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Elite on the BBC Micro

Elite A source (6502SP version)

ELITE A FILE Produces the binary file ELTA.bin that gets loaded by elite-bcfs.asm.
CODE% = &1000 LOAD% = &1000 ORG CODE% LOAD_A% = LOAD%
Name: Parasite variables [View individually] Type: Workspace [Compare versions] Address: &1000 to &100B (&1000 to &100D in the Executive version) Category: Workspaces Summary: Various variables used by the parasite
.MOS SKIP 1 \ This variable appears to be unused .COMC SKIP 1 \ The colour of the dot on the compass \ \ * #WHITE2 = the object in the compass is in front of \ us, so the dot is white \ \ * #GREEN2 = the object in the compass is behind us, \ so the dot is green .DNOIZ SKIP 1 \ Sound on/off configuration setting \ \ * 0 = sound is on (default) \ \ * Non-zero = sound is off \ \ Toggled by pressing "S" when paused, see the DK4 \ routine for details .DAMP SKIP 1 \ Keyboard damping configuration setting \ \ * 0 = damping is enabled (default) \ \ * &FF = damping is disabled \ \ Toggled by pressing CAPS LOCK when paused, see the \ DKS3 routine for details .DJD SKIP 1 \ Keyboard auto-recentre configuration setting \ \ * 0 = auto-recentre is enabled (default) \ \ * &FF = auto-recentre is disabled \ \ Toggled by pressing "A" when paused, see the DKS3 \ routine for details .PATG SKIP 1 \ Configuration setting to show the author names on the \ start-up screen and enable manual hyperspace mis-jumps \ \ * 0 = no author names or manual mis-jumps (default) \ \ * &FF = show author names and allow manual mis-jumps \ \ Toggled by pressing "X" when paused, see the DKS3 \ routine for details \ \ This needs to be turned on for manual mis-jumps to be \ possible. To do a manual mis-jump, first toggle the \ author display by pausing the game (COPY) and pressing \ "X", and during the next hyperspace, hold down CTRL to \ force a mis-jump. See routine ee5 for the "AND PATG" \ instruction that implements this logic .FLH SKIP 1 \ Flashing console bars configuration setting \ \ * 0 = static bars (default) \ \ * &FF = flashing bars \ \ Toggled by pressing "F" when paused, see the DKS3 \ routine for details .JSTGY SKIP 1 \ Reverse joystick Y-channel configuration setting \ \ * 0 = standard Y-channel (default) \ \ * &FF = reversed Y-channel \ \ Toggled by pressing "Y" when paused, see the DKS3 \ routine for details .JSTE SKIP 1 \ Reverse both joystick channels configuration setting \ \ * 0 = standard channels (default) \ \ * &FF = reversed channels \ \ Toggled by pressing "J" when paused, see the DKS3 \ routine for details .JSTK SKIP 1 \ Keyboard or joystick configuration setting \ \ * 0 = keyboard (default) \ \ * &FF = joystick \ \ Toggled by pressing "K" when paused, see the DKS3 \ routine for details IF _EXECUTIVE .JUMP SKIP 1 \ Infinite jump range configuration setting \ \ * 0 = maximum jump range is the standard 7 light \ years (default) \ \ * Non-zero = jump range is infinite \ \ Toggled by pressing "@" when paused, see the DK4 \ routine for details \ \ Not only is the jump range infinite, but you don't use \ any fuel when jumping, either .SPEAK SKIP 1 \ Speech configuration setting \ \ * 0 = speech is disabled (default) \ \ * Non-zero = speech is enabled \ \ Toggled by pressing ":" when paused, see the DK4 \ routine for details \ \ For speech to work, the BBC must be fitted with a \ Watford Electronics Beeb Speech Synthesiser ENDIF .BSTK SKIP 1 \ Bitstik configuration setting \ \ * 0 = keyboard or joystick (default) \ \ * &FF = Bitstik \ \ Toggled by pressing "B" when paused, see the DKS3 \ routine for details .CATF SKIP 1 \ This byte appears to be unused (the CATF variable in \ the I/O processor code is used to store the CATF flag, \ not this one) .ZIP SKIP 0 \ This label is not used but is in the original source
Name: S1% [View individually] Type: Variable Category: Save and load Summary: The drive and directory number used when saving or loading a commander file Deep dive: Commander save files.
The drive part of this string (the "0") is updated with the chosen drive in the QUS1 routine, but the directory part (the "E") is fixed. The variable is followed directly by the commander file at NA%, which starts with the commander name, so the full string at S1% is in the format ":0.E.JAMESON", which gives the full filename of the commander file.
.S1% EQUS ":0.E."
Name: NA% [View individually] Type: Variable [Compare versions] Category: Save and load Summary: The data block for the last saved commander Deep dive: Commander save files The competition code
Contains the last saved commander data, with the name at NA% and the data at NA%+8 onwards. The size of the data block is given in NT% (which also includes the two checksum bytes that follow this block). This block is initially set up with the default commander, which can be maxed out for testing purposes by setting Q% to TRUE. The commander's name is stored at NA%, and can be up to 7 characters long (the DFS filename limit). It is terminated with a carriage return character, ASCII 13. The offset of each byte within a saved commander file is also shown as #0, #1 and so on, so the kill tally, for example, is in bytes #71 and #72 of the saved file. The related variable name from the current commander block is also shown.
.NA% IF _SNG45 OR _SOURCE_DISC EQUS "JAMESON" \ The current commander name, which defaults to JAMESON EQUB 13 \ \ The commander name can be up to seven characters (the \ DFS limit for file names), and is terminated by a \ carriage return ELIF _EXECUTIVE EQUS "FIREBUD" \ The current commander name, which defaults to FIREBUD EQUB 13 \ in the Executive version (this version comes with a \ maxed-out commander by default, so it gets a different \ name, which is presumably a seven-character riff on \ "Firebird", the publishers of the non-Acorn versions \ of Elite) \ \ The commander name can be up to seven characters (the \ DFS limit for file names), and is terminated by a \ carriage return ENDIF \ NA%+8 is the start of the commander data block \ \ This block contains the last saved commander data \ block. As the game is played it uses an identical \ block at location TP to store the current commander \ state, and that block is copied here when the game is \ saved. Conversely, when the game starts up, the block \ here is copied to TP, which restores the last saved \ commander when we die \ \ The initial state of this block defines the default \ commander. Q% can be set to TRUE to give the default \ commander lots of credits and equipment EQUB 0 \ TP = Mission status, #0 EQUB 20 \ QQ0 = Current system X-coordinate (Lave), #1 EQUB 173 \ QQ1 = Current system Y-coordinate (Lave), #2 EQUW &5A4A \ QQ21 = Seed s0 for system 0, galaxy 0 (Tibedied), #3-4 EQUW &0248 \ QQ21 = Seed s1 for system 0, galaxy 0 (Tibedied), #5-6 EQUW &B753 \ QQ21 = Seed s2 for system 0, galaxy 0 (Tibedied), #7-8 IF Q% EQUD &00CA9A3B \ CASH = Amount of cash (100,000,000 Cr), #9-12 ELSE EQUD &E8030000 \ CASH = Amount of cash (100 Cr), #9-12 ENDIF EQUB 70 \ QQ14 = Fuel level, #13 IF _SNG45 OR _SOURCE_DISC EQUB 0 \ COK = Competition flags, #14 ELIF _EXECUTIVE EQUB %10000000 \ COK = Competition flags, #14 ENDIF EQUB 0 \ GCNT = Galaxy number, 0-7, #15 EQUB POW+(128 AND Q%) \ LASER = Front laser, #16 EQUB (POW+128) AND Q% \ LASER+1 = Rear laser, #17 EQUB 0 \ LASER+2 = Left laser, #18 EQUB 0 \ LASER+3 = Right laser, #19 EQUW 0 \ These bytes appear to be unused (they were originally \ used for up/down lasers, but they were dropped), \ #20-21 EQUB 22+(15 AND Q%) \ CRGO = Cargo capacity, #22 EQUB 0 \ QQ20+0 = Amount of Food in cargo hold, #23 EQUB 0 \ QQ20+1 = Amount of Textiles in cargo hold, #24 EQUB 0 \ QQ20+2 = Amount of Radioactives in cargo hold, #25 EQUB 0 \ QQ20+3 = Amount of Slaves in cargo hold, #26 EQUB 0 \ QQ20+4 = Amount of Liquor/Wines in cargo hold, #27 EQUB 0 \ QQ20+5 = Amount of Luxuries in cargo hold, #28 EQUB 0 \ QQ20+6 = Amount of Narcotics in cargo hold, #29 EQUB 0 \ QQ20+7 = Amount of Computers in cargo hold, #30 EQUB 0 \ QQ20+8 = Amount of Machinery in cargo hold, #31 EQUB 0 \ QQ20+9 = Amount of Alloys in cargo hold, #32 EQUB 0 \ QQ20+10 = Amount of Firearms in cargo hold, #33 EQUB 0 \ QQ20+11 = Amount of Furs in cargo hold, #34 EQUB 0 \ QQ20+12 = Amount of Minerals in cargo hold, #35 EQUB 0 \ QQ20+13 = Amount of Gold in cargo hold, #36 EQUB 0 \ QQ20+14 = Amount of Platinum in cargo hold, #37 EQUB 0 \ QQ20+15 = Amount of Gem-Stones in cargo hold, #38 EQUB 0 \ QQ20+16 = Amount of Alien Items in cargo hold, #39 EQUB Q% \ ECM = E.C.M., #40 EQUB Q% \ BST = Fuel scoops ("barrel status"), #41 EQUB Q% AND 127 \ BOMB = Energy bomb, #42 EQUB Q% AND 1 \ ENGY = Energy/shield level, #43 EQUB Q% \ DKCMP = Docking computer, #44 EQUB Q% \ GHYP = Galactic hyperdrive, #45 EQUB Q% \ ESCP = Escape pod, #46 EQUD 0 \ These four bytes appear to be unused, #47-50 EQUB 3+(Q% AND 1) \ NOMSL = Number of missiles, #51 EQUB 0 \ FIST = Legal status ("fugitive/innocent status"), #52 EQUB 16 \ AVL+0 = Market availability of Food, #53 EQUB 15 \ AVL+1 = Market availability of Textiles, #54 EQUB 17 \ AVL+2 = Market availability of Radioactives, #55 EQUB 0 \ AVL+3 = Market availability of Slaves, #56 EQUB 3 \ AVL+4 = Market availability of Liquor/Wines, #57 EQUB 28 \ AVL+5 = Market availability of Luxuries, #58 EQUB 14 \ AVL+6 = Market availability of Narcotics, #59 EQUB 0 \ AVL+7 = Market availability of Computers, #60 EQUB 0 \ AVL+8 = Market availability of Machinery, #61 EQUB 10 \ AVL+9 = Market availability of Alloys, #62 EQUB 0 \ AVL+10 = Market availability of Firearms, #63 EQUB 17 \ AVL+11 = Market availability of Furs, #64 EQUB 58 \ AVL+12 = Market availability of Minerals, #65 EQUB 7 \ AVL+13 = Market availability of Gold, #66 EQUB 9 \ AVL+14 = Market availability of Platinum, #67 EQUB 8 \ AVL+15 = Market availability of Gem-Stones, #68 EQUB 0 \ AVL+16 = Market availability of Alien Items, #69 EQUB 0 \ QQ26 = Random byte that changes for each visit to a \ system, for randomising market prices, #70 EQUW 0 \ TALLY = Number of kills, #71-72 EQUB 128 \ SVC = Save count, #73
Name: CHK2 [View individually] Type: Variable [Compare versions] Category: Save and load Summary: Second checksum byte for the saved commander data file Deep dive: Commander save files The competition code
Second commander checksum byte. If the default commander is changed, a new checksum will be calculated and inserted by the elite-checksum.py script. The offset of this byte within a saved commander file is also shown (it's at byte #74).
.CHK2 IF _SNG45 OR _SOURCE_DISC EQUB &03 EOR &A9 \ The checksum value for the default commander, EOR'd \ with &A9 to make it harder to tamper with the checksum \ byte, #74 ELIF _EXECUTIVE EQUB &3F EOR &A9 \ The checksum value for the maxed-out default \ commander, EOR'd with &A9 to make it harder to tamper \ with the checksum byte, #74 ENDIF
Name: CHK [View individually] Type: Variable [Compare versions] Category: Save and load Summary: First checksum byte for the saved commander data file Deep dive: Commander save files The competition code
Commander checksum byte. If the default commander is changed, a new checksum will be calculated and inserted by the elite-checksum.py script. The offset of this byte within a saved commander file is also shown (it's at byte #75).
.CHK IF _SNG45 OR _SOURCE_DISC EQUB &03 \ The checksum value for the default commander, #75 ELIF _EXECUTIVE EQUB &3F \ The checksum value for the maxed-out default \ commander, #75 ENDIF
Name: S% [View individually] Type: Subroutine Category: Loader Summary: Checksum, decrypt and unscramble the main game code, and start the game
This routine reverses the three copy protection mechanisms that the Big Code File puts in place: the checksum in Checksum, the encryption in DEEOR, and the code reversal in do65c02. In the BeebAsm version here, these three protections are applied by elite-checksum.py, and the original 6502 assembly language versions of the three encryption routines can be found in the elite-checksum.asm file. It also adds in a bit of Tube-specific copy protection, by transmitting the do65c02 routine over the Tube before it is run. It's very crafty stuff!
EQUD 0 \ These bytes appear to be unused RTS \ The checksum byte goes here, at S%-1. In the original \ source this byte is set by the first call to ZP in the \ Big Code File, though in the BeebAsm version this is \ populated by elite-checksum.py .S% CLD \ Clear the D flag to make sure we are in binary mode SEC \ Set the C flag LDA #LO(G%) \ Set (1 0) = SC(1 0) = G% STA 0 STA SC LDA #HI(G%) STA 1 STA SC+1 LDA #LO(F%-1) \ Set (3 2) = F% - 1 STA 2 LDA #HI(F%-1) STA 3 LDX #LO(prtblock) \ Set (Y X) to point to the prtblock parameter block LDY #HI(prtblock) LDA #249 \ Send an OSWORD 249 command to the I/O processor, which JSR OSWORD \ copies the code of the do65c02 routine from the I/O \ processor to prtblock+2 LDX #SC \ Set X = SC, and because SC is in zero page, this means \ that X contains the whole value of SC, so jumping to \ (X), for example, would jump to the address in SC(1 0) EQUB &AD \ This is the opcode for an LDA absolute instruction, so \ it converts the two OSWORD size bytes at prtblock into \ a harmless LDA &2702 instruction .prtblock EQUB 2 \ The number of bytes to transmit with this command EQUB &27 \ The number of bytes to receive with this command JMP (SC,X) \ This block, between here and G%, is overwritten by the PHP \ code of the do65c02 routine from the I/O processor, so PHY \ this code is never run and is presumably just here to LDA #&34 \ throw the crackers off the scent - it just needs to be PHA \ at least as long as the do65c02 routine, which ends LDX #0 \ with a jump to G% below to start the game RTS BRK EQUS "ELITE - By Ian Bell & David Braben" EQUB 10 EQUB 13 BRK LDA SC \ This section of unused code is particularly useful to ADC 2 \ hackers, as it contains the value of F% (in the CMP F%-1 \ CMP F%-1 instruction), which we need to undo the BNE P%-2 \ encryption. We also need the value of G%, which is EQUD &7547534 \ easy enough to work out as it's just after this block. EQUD &452365 \ See the elite-decrypt.py script for more details EQUB &8D .G% JSR DEEOR \ Decrypt the main game code between &1300 and &9FFF JSR COLD \ Copy the recursive tokens and ship blueprints to their \ correct locations JSR Checksum \ Checksum the code from &1000 to &9FFF and check it \ against S%-1 JMP BEGIN \ Jump to BEGIN to start the game NOP \ This instruction is not used
Name: DEEOR [View individually] Type: Subroutine Category: Copy protection Summary: Decrypt bytes between &1300 and &9FFF by EOR'ing them with their page offset
In the original source, the bytes between &1300 and &9FFF are EOR'd by the first call to SC in the Big Code File, though in the BeebAsm version they are EOR'd by elite-checksum.py. The original 6502 assembly language version of the SC routine can be found in the elite-checksum.asm file.
.DEEOR LDY #0 \ Set (X Y) = SC(1 0) = &1300 STY SC LDX #&13 .DEEL STX SC+1 \ Set SC+1 = X, so now SC(1 0) = (X 0) TYA \ Set A = contents of (SC(1 0) + Y) EOR Y EOR &75 EOR (SC),Y \ = contents of ((X 0) + Y) EOR Y EOR &75 EOR #&75 \ = contents of (X Y) EOR Y EOR &75 IF _REMOVE_CHECKSUMS NOP \ If we have disabled checksums, then don't update (X Y) NOP \ with the result, and just move on to the next byte ELSE STA (SC),Y \ Store the EOR'd value in SC(1 0) + Y, i.e. (X Y) ENDIF DEY \ Decrement the loop counter to process the next byte BNE DEEL \ Loop back until we have done the whole page INX \ Increment the page counter to point to the next page CPX #&A0 \ Loop back to do the next page until X = &A0, when BNE DEEL \ (X Y) = &A000 JMP BRKBK \ Jump to BRKBK to set the standard BRKV handler for the \ game and return from the subroutine using a tail call
Name: DOENTRY [View individually] Type: Subroutine [Compare versions] Category: Flight Summary: Dock at the space station, show the ship hanger and work out any mission progression
.DOENTRY JSR RES2 \ Reset a number of flight variables and workspaces JSR LAUN \ Show the space station docking tunnel STZ DELTA \ Reduce the speed to 0 STZ QQ22+1 \ Reset the on-screen hyperspace counter STZ GNTMP \ Cool down the lasers completely LDA #&FF \ Recharge the forward and aft shields STA FSH STA ASH STA ENERGY \ Recharge the energy banks JSR HALL \ Show the ship hanger LDY #44 \ Wait for 44/50 of a second (0.88 seconds) JSR DELAY LDA TP \ Fetch bits 0 and 1 of TP, and if they are non-zero AND #%00000011 \ (i.e. mission 1 is either in progress or has been BNE EN1 \ completed), skip to EN1 LDA TALLY+1 \ If the high byte of TALLY is zero (so we have a combat BEQ EN4 \ rank below Competent), jump to EN4 as we are not yet \ good enough to qualify for a mission LDA GCNT \ Fetch the galaxy number into A, and if any of bits 1-7 LSR A \ are set (i.e. A > 1), jump to EN4 as mission 1 can BNE EN4 \ only be triggered in the first two galaxies JMP BRIEF \ If we get here, mission 1 hasn't started, we have \ reached a combat rank of Competent, and we are in \ galaxy 0 or 1 (shown in-game as galaxy 1 or 2), so \ it's time to start mission 1 by calling BRIEF .EN1 \ If we get here then mission 1 is either in progress or \ has been completed CMP #%00000011 \ If bits 0 and 1 are not both set, then jump to EN2 BNE EN2 JMP DEBRIEF \ Bits 0 and 1 are both set, so mission 1 is both in \ progress and has been completed, which means we have \ only just completed it, so jump to DEBRIEF to end the \ mission get our reward .EN2 \ Mission 1 has been completed, so now to check for \ mission 2 LDA GCNT \ Fetch the galaxy number into A CMP #2 \ If this is not galaxy 2 (shown in-game as galaxy 3), BNE EN4 \ jump to EN4 as we can only start mission 2 in the \ third galaxy LDA TP \ Extract bits 0-3 of TP into A AND #%00001111 CMP #%00000010 \ If mission 1 is complete and no longer in progress, BNE EN3 \ and mission 2 is not yet started, then bits 0-3 of TP \ will be %0010, so this jumps to EN3 if this is not the \ case LDA TALLY+1 \ If the high byte of TALLY is < 5 (so we have a combat CMP #5 \ rank that is less than 3/8 of the way from Dangerous BCC EN4 \ to Deadly), jump to EN4 as our rank isn't high enough \ for mission 2 JMP BRIEF2 \ If we get here, mission 1 is complete and no longer in \ progress, mission 2 hasn't started, we have reached a \ combat rank of 3/8 of the way from Dangerous to \ Deadly, and we are in galaxy 2 (shown in-game as \ galaxy 3), so it's time to start mission 2 by calling \ BRIEF2 .EN3 CMP #%00000110 \ If mission 1 is complete and no longer in progress, BNE EN5 \ and mission 2 has started but we have not yet been \ briefed and picked up the plans, then bits 0-3 of TP \ will be %0110, so this jumps to EN5 if this is not the \ case LDA QQ0 \ Set A = the current system's galactic x-coordinate CMP #215 \ If A <> 215 then jump to EN4 BNE EN4 LDA QQ1 \ Set A = the current system's galactic y-coordinate CMP #84 \ If A <> 84 then jump to EN4 BNE EN4 JMP BRIEF3 \ If we get here, mission 1 is complete and no longer in \ progress, mission 2 has started but we have not yet \ picked up the plans, and we have just arrived at \ Ceerdi at galactic coordinates (215, 84), so we jump \ to BRIEF3 to get a mission brief and pick up the plans \ that we need to carry to Birera .EN5 CMP #%00001010 \ If mission 1 is complete and no longer in progress, BNE EN4 \ and mission 2 has started and we have picked up the \ plans, then bits 0-3 of TP will be %1010, so this \ jumps to EN5 if this is not the case LDA QQ0 \ Set A = the current system's galactic x-coordinate CMP #63 \ If A <> 63 then jump to EN4 BNE EN4 LDA QQ1 \ Set A = the current system's galactic y-coordinate CMP #72 BNE EN4 \ If A <> 72 then jump to EN4 JMP DEBRIEF2 \ If we get here, mission 1 is complete and no longer in \ progress, mission 2 has started and we have picked up \ the plans, and we have just arrived at Birera at \ galactic coordinates (63, 72), so we jump to DEBRIEF2 \ to end the mission and get our reward .EN4 JMP BAY \ If we get here them we didn't start or any missions, \ so jump to BAY to go to the docking bay (i.e. show the \ Status Mode screen)
Name: BRKBK [View individually] Type: Subroutine [Compare versions] Category: Save and load Summary: Set the standard BRKV handler for the game
BRKV is set to this routine by the BRKBK routine, which is called by the decryption routine at DEEOR just before the game is run for the first time, and at the end of the SVE routine after the disc access menu has been processed (so this resets BRKV to the standard BRKV handler for the game).
.BRKBK LDA #LO(BRBR) \ Set BRKV to point to the BRBR routine, disabling SEI \ interrupts while we make the change and re-enabling STA BRKV \ them once we are done LDA #HI(BRBR) STA BRKV+1 CLI RTS \ Return from the subroutine
Name: Main flight loop (Part 1 of 16) [View individually] Type: Subroutine [Compare versions] Category: Main loop Summary: Seed the random number generator Deep dive: Program flow of the main game loop Generating random numbers
The main flight loop covers most of the flight-specific aspects of Elite. This section covers the following: * Seed the random number generator Other entry points: M% The entry point for the main flight loop
.M% LDA K% \ We want to seed the random number generator with a \ pretty random number, so fetch the contents of K%, \ which is the x_lo coordinate of the planet. This value \ will be fairly unpredictable, so it's a pretty good \ candidate STA RAND \ Store the seed in the first byte of the four-byte \ random number seed that's stored in RAND
Name: Main flight loop (Part 2 of 16) [View individually] Type: Subroutine [Compare versions] Category: Main loop Summary: Calculate the alpha and beta angles from the current pitch and roll of our ship Deep dive: Program flow of the main game loop Pitching and rolling
The main flight loop covers most of the flight-specific aspects of Elite. This section covers the following: * Calculate the alpha and beta angles from the current pitch and roll Here we take the current rate of pitch and roll, as set by the joystick or keyboard, and convert them into alpha and beta angles that we can use in the matrix functions to rotate space around our ship. The alpha angle covers roll, while the beta angle covers pitch (there is no yaw in this version of Elite). The angles are in radians, which allows us to use the small angle approximation when moving objects in the sky (see the MVEIT routine for more on this). Also, the signs of the two angles are stored separately, in both the sign and the flipped sign, as this makes calculations easier.
LDX JSTX \ Set X to the current rate of roll in JSTX, and JSR cntr \ apply keyboard damping twice (if enabled) so the roll JSR cntr \ rate in X creeps towards the centre by 2 \ The roll rate in JSTX increases if we press ">" (and \ the RL indicator on the dashboard goes to the right). \ This rolls our ship to the right (clockwise), but we \ actually implement this by rolling everything else \ to the left (anticlockwise), so a positive roll rate \ in JSTX translates to a negative roll angle alpha TXA \ Set A and Y to the roll rate but with the sign bit EOR #%10000000 \ flipped (i.e. set them to the sign we want for alpha) TAY AND #%10000000 \ Extract the flipped sign of the roll rate and store STA ALP2 \ in ALP2 (so ALP2 contains the sign of the roll angle \ alpha) STX JSTX \ Update JSTX with the damped value that's still in X EOR #%10000000 \ Extract the correct sign of the roll rate and store STA ALP2+1 \ in ALP2+1 (so ALP2+1 contains the flipped sign of the \ roll angle alpha) TYA \ Set A to the roll rate but with the sign bit flipped BPL P%+7 \ If the value of A is positive, skip the following \ three instructions EOR #%11111111 \ A is negative, so change the sign of A using two's CLC \ complement so that A is now positive and contains ADC #1 \ the absolute value of the roll rate, i.e. |JSTX| LSR A \ Divide the (positive) roll rate in A by 4 LSR A CMP #8 \ If A >= 8, skip the following instruction BCS P%+3 LSR A \ A < 8, so halve A again STA ALP1 \ Store A in ALP1, so we now have: \ \ ALP1 = |JSTX| / 8 if |JSTX| < 32 \ \ ALP1 = |JSTX| / 4 if |JSTX| >= 32 \ \ This means that at lower roll rates, the roll angle is \ reduced closer to zero than at higher roll rates, \ which gives us finer control over the ship's roll at \ lower roll rates \ \ Because JSTX is in the range -127 to +127, ALP1 is \ in the range 0 to 31 ORA ALP2 \ Store A in ALPHA, but with the sign set to ALP2 (so STA ALPHA \ ALPHA has a different sign to the actual roll rate) LDX JSTY \ Set X to the current rate of pitch in JSTY, and JSR cntr \ apply keyboard damping so the pitch rate in X creeps \ towards the centre by 1 TXA \ Set A and Y to the pitch rate but with the sign bit EOR #%10000000 \ flipped TAY AND #%10000000 \ Extract the flipped sign of the pitch rate into A STX JSTY \ Update JSTY with the damped value that's still in X STA BET2+1 \ Store the flipped sign of the pitch rate in BET2+1 EOR #%10000000 \ Extract the correct sign of the pitch rate and store STA BET2 \ it in BET2 TYA \ Set A to the pitch rate but with the sign bit flipped BPL P%+4 \ If the value of A is positive, skip the following \ instruction EOR #%11111111 \ A is negative, so flip the bits ADC #4 \ Add 4 to the (positive) pitch rate, so the maximum \ value is now up to 131 (rather than 127) LSR A \ Divide the (positive) pitch rate in A by 16 LSR A LSR A LSR A CMP #3 \ If A >= 3, skip the following instruction BCS P%+3 LSR A \ A < 3, so halve A again STA BET1 \ Store A in BET1, so we now have: \ \ BET1 = |JSTY| / 32 if |JSTY| < 48 \ \ BET1 = |JSTY| / 16 if |JSTY| >= 48 \ \ This means that at lower pitch rates, the pitch angle \ is reduced closer to zero than at higher pitch rates, \ which gives us finer control over the ship's pitch at \ lower pitch rates \ \ Because JSTY is in the range -131 to +131, BET1 is in \ the range 0 to 8 ORA BET2 \ Store A in BETA, but with the sign set to BET2 (so STA BETA \ BETA has the same sign as the actual pitch rate) LDA BSTK \ If BSTK = 0 then the Bitstik is not configured, so BEQ BS2 \ jump to BS2 to skip the following LDA KTRAN+10 \ Fetch the Bitstik rotation value (high byte) from the \ key logger buffer LSR A \ Divide A by 4 LSR A CMP #40 \ If A < 40, skip the following instruction BCC P%+4 LDA #40 \ Set A = 40, which ensures a maximum speed of 40 STA DELTA \ Update our speed in DELTA BNE MA4 \ If the speed we just set is non-zero, then jump to MA4 \ to skip the following, as we don't need to check the \ keyboard for speed keys, otherwise do check the \ keyboard (so Bitstik users can still use the keyboard \ for speed adjustments if they twist the stick to zero)
Name: Main flight loop (Part 3 of 16) [View individually] Type: Subroutine [Compare versions] Category: Main loop Summary: Scan for flight keys and process the results Deep dive: Program flow of the main game loop The key logger
The main flight loop covers most of the flight-specific aspects of Elite. This section covers the following: * Scan for flight keys and process the results Flight keys are logged in the key logger at location KY1 onwards, with a non-zero value in the relevant location indicating a key press. See the deep dive on "The key logger" for more details. The key presses that are processed are as follows: * Space and "?" to speed up and slow down * "U", "T" and "M" to disarm, arm and fire missiles * TAB to fire an energy bomb * ESCAPE to launch an escape pod * "J" to initiate an in-system jump * "E" to deploy E.C.M. anti-missile countermeasures * "C" to use the docking computer * "A" to fire lasers
.BS2 LDA KY2 \ If Space is being pressed, keep going, otherwise jump BEQ MA17 \ down to MA17 to skip the following LDA DELTA \ The "go faster" key is being pressed, so first we CMP #40 \ fetch the current speed from DELTA into A, and if BCS MA17 \ A >= 40, we are already going at full pelt, so jump \ down to MA17 to skip the following INC DELTA \ We can go a bit faster, so increment the speed in \ location DELTA .MA17 LDA KY1 \ If "?" is being pressed, keep going, otherwise jump BEQ MA4 \ down to MA4 to skip the following DEC DELTA \ The "slow down" key is being pressed, so we decrement \ the current ship speed in DELTA BNE MA4 \ If the speed is still greater than zero, jump to MA4 INC DELTA \ Otherwise we just braked a little too hard, so bump \ the speed back up to the minimum value of 1 .MA4 LDA KY15 \ If "U" is being pressed and the number of missiles AND NOMSL \ in NOMSL is non-zero, keep going, otherwise jump down BEQ MA20 \ to MA20 to skip the following LDY #GREEN2 \ The "disarm missiles" key is being pressed, so call JSR ABORT \ ABORT to disarm the missile and update the missile \ indicators on the dashboard to green (Y = &EE) LDA #40 \ Call the NOISE routine with A = 40 to make a low, JSR NOISE \ long beep to indicate the missile is now disarmed LDA #0 \ Set MSAR to 0 to indicate that no missiles are STA MSAR \ currently armed .MA20 LDA MSTG \ If MSTG is positive (i.e. it does not have bit 7 set), BPL MA25 \ then it indicates we already have a missile locked on \ a target (in which case MSTG contains the ship number \ of the target), so jump to MA25 to skip targeting. Or \ to put it another way, if MSTG = &FF, which means \ there is no current target lock, keep going LDA KY14 \ If "T" is being pressed, keep going, otherwise jump BEQ MA25 \ down to MA25 to skip the following LDX NOMSL \ If the number of missiles in NOMSL is zero, jump down BEQ MA25 \ to MA25 to skip the following STA MSAR \ The "target missile" key is being pressed and we have \ at least one missile, so set MSAR = &FF to denote that \ our missile is currently armed (we know A has the \ value &FF, as we just loaded it from MSTG and checked \ that it was negative) LDY #YELLOW2 \ Change the leftmost missile indicator to yellow JSR MSBAR \ on the missile bar (this call changes the leftmost \ indicator because we set X to the number of missiles \ in NOMSL above, and the indicators are numbered from \ right to left, so X is the number of the leftmost \ indicator) .MA25 LDA KY16 \ If "M" is being pressed, keep going, otherwise jump BEQ MA24 \ down to MA24 to skip the following LDA MSTG \ If MSTG = &FF then there is no target lock, so jump to BMI MA64 \ MA64 to skip the following (also skipping the checks \ for TAB, ESCAPE, "J" and "E") JSR FRMIS \ The "fire missile" key is being pressed and we have \ a missile lock, so call the FRMIS routine to fire \ the missile .MA24 LDA KY12 \ If TAB is being pressed, keep going, otherwise jump BEQ MA76 \ jump down to MA76 to skip the following ASL BOMB \ The "energy bomb" key is being pressed, so double \ the value in BOMB. If we have an energy bomb fitted, \ BOMB will contain &7F (%01111111) before this shift \ and will contain &FE (%11111110) after the shift; if \ we don't have an energy bomb fitted, BOMB will still \ contain 0. The bomb explosion is dealt with in the \ MAL1 routine below - this just registers the fact that \ we've set the bomb ticking .MA76 LDA KY20 \ If "P" is being pressed, keep going, otherwise skip BEQ MA78 \ the next two instructions LDA #0 \ The "cancel docking computer" key is bring pressed, STA auto \ so turn it off by setting auto to 0 .MA78 LDA KY13 \ If ESCAPE is being pressed and we have an escape pod AND ESCP \ fitted, keep going, otherwise jump to noescp to skip BEQ noescp \ the following instructions LDA MJ \ If we are in witchspace, we can't launch our escape BNE noescp \ pod, so jump down to noescp JMP ESCAPE \ The "launch escape pod" button is being pressed and \ we have an escape pod fitted, so jump to ESCAPE to \ launch it, and exit the main flight loop using a tail \ call .noescp LDA KY18 \ If "J" is being pressed, keep going, otherwise skip BEQ P%+5 \ the next instruction JSR WARP \ Call the WARP routine to do an in-system jump LDA KY17 \ If "E" is being pressed and we have an E.C.M. fitted, AND ECM \ keep going, otherwise jump down to MA64 to skip the BEQ MA64 \ following LDA ECMA \ If ECMA is non-zero, that means an E.C.M. is already BNE MA64 \ operating and is counting down (this can be either \ our E.C.M. or an opponent's), so jump down to MA64 to \ skip the following (as we can't have two E.C.M. \ systems operating at the same time) DEC ECMP \ The "E.C.M." button is being pressed and nobody else \ is operating their E.C.M., so decrease the value of \ ECMP to make it non-zero, to denote that our E.C.M. \ is now on JSR ECBLB2 \ Call ECBLB2 to light up the E.C.M. indicator bulb on \ the dashboard, set the E.C.M. countdown timer to 32, \ and start making the E.C.M. sound .MA64 LDA KY19 \ If "C" is being pressed, and we have a docking AND DKCMP \ computer fitted, keep going, otherwise jump down to BEQ MA68 \ MA68 to skip the following STA auto \ Set auto to the non-zero value of A, so the docking \ computer is activated .MA68 LDA #0 \ Set LAS = 0, to switch the laser off while we do the STA LAS \ following logic STA DELT4 \ Take the 16-bit value (DELTA 0) - i.e. a two-byte LDA DELTA \ number with DELTA as the high byte and 0 as the low LSR A \ byte - and divide it by 4, storing the 16-bit result ROR DELT4 \ in DELT4(1 0). This has the effect of storing the LSR A \ current speed * 64 in the 16-bit location DELT4(1 0) ROR DELT4 STA DELT4+1 LDA LASCT \ If LASCT is zero, keep going, otherwise the laser is BNE MA3 \ a pulse laser that is between pulses, so jump down to \ MA3 to skip the following LDA KY7 \ If "A" is being pressed, keep going, otherwise jump BEQ MA3 \ down to MA3 to skip the following LDA GNTMP \ If the laser temperature >= 242 then the laser has CMP #242 \ overheated, so jump down to MA3 to skip the following BCS MA3 LDX VIEW \ If the current space view has a laser fitted (i.e. the LDA LASER,X \ laser power for this view is greater than zero), then BEQ MA3 \ keep going, otherwise jump down to MA3 to skip the \ following \ If we get here, then the "fire" button is being \ pressed, our laser hasn't overheated and isn't already \ being fired, and we actually have a laser fitted to \ the current space view, so it's time to hit me with \ those laser beams PHA \ Store the current view's laser power on the stack AND #%01111111 \ Set LAS and LAS2 to bits 0-6 of the laser power STA LAS STA LAS2 LDA #0 \ Call the NOISE routine with A = 0 to make the sound JSR NOISE \ of our laser firing JSR LASLI \ Call LASLI to draw the laser lines PLA \ Restore the current view's laser power into A BPL ma1 \ If the laser power has bit 7 set, then it's an "always \ on" laser rather than a pulsing laser, so keep going, \ otherwise jump down to ma1 to skip the following \ instruction LDA #0 \ This is an "always on" laser (i.e. a beam laser, \ as the cassette version of Elite doesn't have military \ lasers), so set A = 0, which will be stored in LASCT \ to denote that this is not a pulsing laser .ma1 AND #%11111010 \ LASCT will be set to 0 for beam lasers, and to the STA LASCT \ laser power AND %11111010 for pulse lasers, which \ comes to 10 (as pulse lasers have a power of 15). See \ MA23 below for more on laser pulsing and LASCT
Name: Main flight loop (Part 4 of 16) [View individually] Type: Subroutine [Compare versions] Category: Main loop Summary: For each nearby ship: Copy the ship's data block from K% to the zero-page workspace at INWK Deep dive: Program flow of the main game loop Ship data blocks
The main flight loop covers most of the flight-specific aspects of Elite. This section covers the following: * Start looping through all the ships in the local bubble, and for each one: * Copy the ship's data block from K% to INWK * Set XX0 to point to the ship's blueprint (if this is a ship) Other entry points: MAL1 Marks the beginning of the ship analysis loop, so we can jump back here from part 12 of the main flight loop to work our way through each ship in the local bubble. We also jump back here when a ship is removed from the bubble, so we can continue processing from the next ship
.MA3 LDX #0 \ We're about to work our way through all the ships in \ our local bubble of universe, so set a counter in X, \ starting from 0, to refer to each ship slot in turn .MAL1 STX XSAV \ Store the current slot number in XSAV LDA FRIN,X \ Fetch the contents of this slot into A. If it is 0 BNE P%+5 \ then this slot is empty and we have no more ships to JMP MA18 \ process, so jump to MA18 below, otherwise A contains \ the type of ship that's in this slot, so skip over the \ JMP MA18 instruction and keep going STA TYPE \ Store the ship type in TYPE JSR GINF \ Call GINF to fetch the address of the ship data block \ for the ship in slot X and store it in INF. The data \ block is in the K% workspace, which is where all the \ ship data blocks are stored \ Next we want to copy the ship data block from INF to \ the zero-page workspace at INWK, so we can process it \ more efficiently LDY #NI%-1 \ There are NI% bytes in each ship data block (and in \ the INWK workspace, so we set a counter in Y so we can \ loop through them .MAL2 LDA (INF),Y \ Load the Y-th byte of INF and store it in the Y-th STA INWK,Y \ byte of INWK DEY \ Decrement the loop counter BPL MAL2 \ Loop back for the next byte until we have copied the \ last byte from INF to INWK LDA TYPE \ If the ship type is negative then this indicates a BMI MA21 \ planet or sun, so jump down to MA21, as the next bit \ sets up a pointer to the ship blueprint, and then \ checks for energy bomb damage, and neither of these \ apply to planets and suns ASL A \ Set Y = ship type * 2 TAY LDA XX21-2,Y \ The ship blueprints at XX21 start with a lookup STA XX0 \ table that points to the individual ship blueprints, \ so this fetches the low byte of this particular ship \ type's blueprint and stores it in XX0 LDA XX21-1,Y \ Fetch the high byte of this particular ship type's STA XX0+1 \ blueprint and store it in XX0+1
Name: Main flight loop (Part 5 of 16) [View individually] Type: Subroutine [Compare versions] Category: Main loop Summary: For each nearby ship: If an energy bomb has been set off, potentially kill this ship Deep dive: Program flow of the main game loop
The main flight loop covers most of the flight-specific aspects of Elite. This section covers the following: * Continue looping through all the ships in the local bubble, and for each one: * If an energy bomb has been set off and this ship can be killed, kill it and increase the kill tally
LDA BOMB \ If we set off our energy bomb (see MA24 above), then BPL MA21 \ BOMB is now negative, so this skips to MA21 if our \ energy bomb is not going off CPY #2*SST \ If the ship in Y is the space station, jump to BA21 BEQ MA21 \ as energy bombs are useless against space stations CPY #2*CON \ If the ship in Y is the Constrictor, jump to BA21 BCS MA21 \ as energy bombs are useless against the Constrictor \ (the Constrictor is the target of mission 1, and it \ would be too easy if it could just be blown out of \ the sky with a single key press) LDA INWK+31 \ If the ship we are checking has bit 5 set in its ship AND #%00100000 \ byte #31, then it is already exploding, so jump to BNE MA21 \ BA21 as ships can't explode more than once ASL INWK+31 \ The energy bomb is killing this ship, so set bit 7 of SEC \ the ship byte #31 to indicate that it has now been ROR INWK+31 \ killed JSR EXNO2 \ Call EXNO2 to process the fact that we have killed a \ ship (so increase the kill tally, make an explosion \ sound and possibly display "RIGHT ON COMMANDER!")
Name: Main flight loop (Part 6 of 16) [View individually] Type: Subroutine Category: Main loop Summary: For each nearby ship: Move the ship in space and copy the updated INWK data block back to K% Deep dive: Program flow of the main game loop Program flow of the ship-moving routine Ship data blocks
The main flight loop covers most of the flight-specific aspects of Elite. This section covers the following: * Continue looping through all the ships in the local bubble, and for each one: * Move the ship in space * Copy the updated ship's data block from INWK back to K%
.MA21 JSR MVEIT \ Call MVEIT to move the ship we are processing in space \ Now that we are done processing this ship, we need to \ copy the ship data back from INWK to the correct place \ in the K% workspace. We already set INF in part 4 to \ point to the ship's data block in K%, so we can simply \ do the reverse of the copy we did before, this time \ copying from INWK to INF LDY #(NI%-1) \ Set a counter in Y so we can loop through the NI% \ bytes in the ship data block .MAL3 LDA INWK,Y \ Load the Y-th byte of INWK and store it in the Y-th STA (INF),Y \ byte of INF DEY \ Decrement the loop counter BPL MAL3 \ Loop back for the next byte, until we have copied the \ last byte from INWK back to INF
Name: Main flight loop (Part 7 of 16) [View individually] Type: Subroutine [Compare versions] Category: Main loop Summary: For each nearby ship: Check whether we are docking, scooping or colliding with it Deep dive: Program flow of the main game loop
The main flight loop covers most of the flight-specific aspects of Elite. This section covers the following: * Continue looping through all the ships in the local bubble, and for each one: * Check how close we are to this ship and work out if we are docking, scooping or colliding with it
LDA INWK+31 \ Fetch the status of this ship from bits 5 (is ship AND #%10100000 \ exploding?) and bit 7 (has ship been killed?) from \ ship byte #31 into A JSR MAS4 \ Or this value with x_hi, y_hi and z_hi BNE MA65 \ If this value is non-zero, then either the ship is \ far away (i.e. has a non-zero high byte in at least \ one of the three axes), or it is already exploding, \ or has been flagged as being killed - in which case \ jump to MA65 to skip the following, as we can't dock \ scoop or collide with it LDA INWK \ Set A = (x_lo OR y_lo OR z_lo), and if bit 7 of the ORA INWK+3 \ result is set, the ship is still a fair distance ORA INWK+6 \ away (further than 127 in at least one axis), so jump BMI MA65 \ to MA65 to skip the following, as it's too far away to \ dock, scoop or collide with LDX TYPE \ If the current ship type is negative then it's either BMI MA65 \ a planet or a sun, so jump down to MA65 to skip the \ following, as we can't dock with it or scoop it CPX #SST \ If this ship is the space station, jump to ISDK to BEQ ISDK \ check whether we are docking with it AND #%11000000 \ If bit 6 of (x_lo OR y_lo OR z_lo) is set, then the BNE MA65 \ ship is still a reasonable distance away (further than \ 63 in at least one axis), so jump to MA65 to skip the \ following, as it's too far away to dock, scoop or \ collide with CPX #MSL \ If this ship is a missile, jump down to MA65 to skip BEQ MA65 \ the following, as we can't scoop or dock with a \ missile, and it has its own dedicated collision \ checks in the TACTICS routine LDA BST \ If we have fuel scoops fitted then BST will be &FF, \ otherwise it will be 0 AND INWK+5 \ Ship byte #5 contains the y_sign of this ship, so a \ negative value here means the canister is below us, \ which means the result of the AND will be negative if \ the canister is below us and we have a fuel scoop \ fitted BPL MA58 \ If the result is positive, then we either have no \ scoop or the canister is above us, and in both cases \ this means we can't scoop the item, so jump to MA58 \ to process a collision
Name: Main flight loop (Part 8 of 16) [View individually] Type: Subroutine [Compare versions] Category: Main loop Summary: For each nearby ship: Process us potentially scooping this item Deep dive: Program flow of the main game loop
The main flight loop covers most of the flight-specific aspects of Elite. This section covers the following: * Continue looping through all the ships in the local bubble, and for each one: * Process us potentially scooping this item
CPX #OIL \ If this is a cargo canister, jump to oily to randomly BEQ oily \ decide the canister's contents LDY #0 \ Fetch byte #0 of the ship's blueprint LDA (XX0),Y LSR A \ Shift it right four times, so A now contains the high LSR A \ nibble (i.e. bits 4-7) LSR A LSR A BEQ MA58 \ If A = 0, jump to MA58 to skip all the docking and \ scooping checks \ Only the Thargon, alloy plate, splinter and escape pod \ have non-zero upper nibbles in their blueprint byte #0 \ so if we get here, our ship is one of those, and the \ upper nibble gives the market item number of the item \ when scooped, less 1 ADC #1 \ Add 1 to the upper nibble to get the market item \ number BNE slvy2 \ Skip to slvy2 so we scoop the ship as a market item .oily JSR DORND \ Set A and X to random numbers and reduce A to a AND #7 \ random number in the range 0-7 .slvy2 \ By the time we get here, we are scooping, and A \ contains the type of item we are scooping (a random \ number 0-7 if we are scooping a cargo canister, 3 if \ we are scooping an escape pod, or 16 if we are \ scooping a Thargon). These numbers correspond to the \ relevant market items (see QQ23 for a list), so a \ cargo canister can contain anything from food to \ computers, while escape pods contain slaves, and \ Thargons become alien items when scooped JSR tnpr1 \ Call tnpr1 with the scooped cargo type stored in A \ to work out whether we have room in the hold for one \ tonne of this cargo (A is set to 1 by this call, and \ the C flag contains the result) LDY #78 \ This instruction has no effect, so presumably it used \ to do something, but didn't get removed BCS MA59 \ If the C flag is set then we have no room in the hold \ for the scooped item, so jump down to MA59 make a \ sound to indicate failure, before destroying the \ canister LDY QQ29 \ Scooping was successful, so set Y to the type of \ item we just scooped, which we stored in QQ29 above ADC QQ20,Y \ Add A (which we set to 1 above) to the number of items STA QQ20,Y \ of type Y in the cargo hold, as we just successfully \ scooped one canister of type Y TYA \ Print recursive token 48 + A as an in-flight token, ADC #208 \ which will be in the range 48 ("FOOD") to 64 ("ALIEN JSR MESS \ ITEMS"), so this prints the scooped item's name ASL NEWB \ The item has now been scooped, so set bit 7 of its SEC \ NEWB flags to indicate this ROR NEWB .MA65 JMP MA26 \ If we get here, then the ship we are processing was \ too far away to be scooped, docked or collided with, \ so jump to MA26 to skip over the collision routines \ and move on to missile targeting
Name: Main flight loop (Part 9 of 16) [View individually] Type: Subroutine [Compare versions] Category: Main loop Summary: For each nearby ship: If it is a space station, check whether we are successfully docking with it Deep dive: Program flow of the main game loop Docking checks
The main flight loop covers most of the flight-specific aspects of Elite. This section covers the following: * Process docking with a space station For details on the various docking checks in this routine, see the deep dive on "Docking checks". Other entry points: GOIN We jump here from part 3 of the main flight loop if the docking computer is activated by pressing "C"
.ISDK LDA K%+NI%+36 \ 1. Fetch the NEWB flags (byte #36) of the second ship AND #%00000100 \ in the ship data workspace at K%, which is reserved BNE MA62 \ for the sun or the space station (in this case it's \ the latter), and if bit 2 is set, meaning the station \ is hostile, jump down to MA62 to fail docking (so \ trying to dock at a station that we have annoyed does \ not end well) LDA INWK+14 \ 2. If nosev_z_hi < 214, jump down to MA62 to fail CMP #214 \ docking, as the angle of approach is greater than 26 BCC MA62 \ degrees JSR SPS1 \ Call SPS1 to calculate the vector to the planet and \ store it in XX15 LDA XX15+2 \ Set A to the z-axis of the vector CMP #89 \ 4. If z-axis < 89, jump to MA62 to fail docking, as BCC MA62 \ we are not in the 22.0 degree safe cone of approach LDA INWK+16 \ 5. If |roofv_x_hi| < 80, jump to MA62 to fail docking, AND #%01111111 \ as the slot is more than 36.6 degrees from horizontal CMP #80 BCC MA62 .GOIN \ If we arrive here, either the docking computer has \ been activated, or we just docked successfully JMP DOENTRY \ Go to the docking bay (i.e. show the ship hanger) .MA62 \ If we arrive here, docking has just failed LDA DELTA \ If the ship's speed is < 5, jump to MA67 to register CMP #5 \ some damage, but not a huge amount BCC MA67 JMP DEATH \ Otherwise we have just crashed into the station, so \ process our death
Name: Main flight loop (Part 10 of 16) [View individually] Type: Subroutine Category: Main loop Summary: For each nearby ship: Remove if scooped, or process collisions Deep dive: Program flow of the main game loop
The main flight loop covers most of the flight-specific aspects of Elite. This section covers the following: * Continue looping through all the ships in the local bubble, and for each one: * Remove scooped item after both successful and failed scoopings * Process collisions
.MA59 \ If we get here then scooping failed JSR EXNO3 \ Make the sound of the cargo canister being destroyed \ and fall through into MA60 to remove the canister \ from our local bubble .MA60 \ If we get here then scooping was successful ASL INWK+31 \ Set bit 7 of the scooped or destroyed item, to denote SEC \ that it has been killed and should be removed from ROR INWK+31 \ the local bubble .MA61 \ This label is not used but is in the original source BNE MA26 \ Jump to MA26 to skip over the collision routines and \ to move on to missile targeting (this BNE is \ effectively a JMP as A will never be zero) .MA67 \ If we get here then we have collided with something, \ but not fatally LDA #1 \ Set the speed in DELTA to 1 (i.e. a sudden stop) STA DELTA LDA #5 \ Set the amount of damage in A to 5 (a small dent) and BNE MA63 \ jump down to MA63 to process the damage (this BNE is \ effectively a JMP as A will never be zero) .MA58 \ If we get here, we have collided with something in a \ potentially fatal way ASL INWK+31 \ Set bit 7 of the ship we just collided with, to SEC \ denote that it has been killed and should be removed ROR INWK+31 \ from the local bubble LDA INWK+35 \ Load A with the energy level of the ship we just hit SEC \ Set the amount of damage in A to 128 + A / 2, so ROR A \ this is quite a big dent, and colliding with higher \ energy ships will cause more damage .MA63 JSR OOPS \ The amount of damage is in A, so call OOPS to reduce \ our shields, and if the shields are gone, there's a \ a chance of cargo loss or even death JSR EXNO3 \ Make the sound of colliding with the other ship and \ fall through into MA26 to try targeting a missile
Name: Main flight loop (Part 11 of 16) [View individually] Type: Subroutine [Compare versions] Category: Main loop Summary: For each nearby ship: Process missile lock and firing our laser Deep dive: Program flow of the main game loop Flipping axes between space views
The main flight loop covers most of the flight-specific aspects of Elite. This section covers the following: * Continue looping through all the ships in the local bubble, and for each one: * If this is not the front space view, flip the axes of the ship's coordinates in INWK * Process missile lock * Process our laser firing
.MA26 LDA NEWB \ If bit 7 of the ship's NEWB flags is clear, skip the BPL P%+5 \ following instruction JSR SCAN \ Bit 7 of the ship's NEWB flags is set, which means the \ ship has docked or been scooped, so we draw the ship \ on the scanner, which has the effect of removing it LDA QQ11 \ If this is not a space view, jump to MA15 to skip BNE MA15 \ missile and laser locking JSR PLUT \ Call PLUT to update the geometric axes in INWK to \ match the view (front, rear, left, right) JSR HITCH \ Call HITCH to see if this ship is in the crosshairs, BCC MA8 \ in which case the C flag will be set (so if there is \ no missile or laser lock, we jump to MA8 to skip the \ following) LDA MSAR \ We have missile lock, so check whether the leftmost BEQ MA47 \ missile is currently armed, and if not, jump to MA47 \ to process laser fire, as we can't lock an unarmed \ missile JSR BEEP \ We have missile lock and an armed missile, so call \ the BEEP subroutine to make a short, high beep LDX XSAV \ Call ABORT2 to store the details of this missile LDY #RED2 \ lock, with the targeted ship's slot number in X JSR ABORT2 \ (which we stored in XSAV at the start of this ship's \ loop at MAL1), and set the colour of the missile \ indicator to the colour in Y (red = &0E) .MA47 \ If we get here then the ship is in our sights, but \ we didn't lock a missile, so let's see if we're \ firing the laser LDA LAS \ If we are firing the laser then LAS will contain the BEQ MA8 \ laser power (which we set in MA68 above), so if this \ is zero, jump down to MA8 to skip the following LDX #15 \ We are firing our laser and the ship in INWK is in JSR EXNO \ the crosshairs, so call EXNO to make the sound of \ us making a laser strike on another ship LDA TYPE \ Did we just hit the space station? If so, jump to CMP #SST \ MA14+2 to make the station hostile, skipping the BEQ MA14+2 \ following as we can't destroy a space station CMP #CON \ If the ship we hit is less than #CON - i.e. it's not BCC BURN \ a Constrictor, Cougar, Dodo station or the Elite logo, \ jump to BURN to skip the following LDA LAS \ Set A to the power of the laser we just used to hit \ the ship (i.e. the laser in the current view) CMP #(Armlas AND 127) \ If the laser is not a military laser, jump to MA14+2 BNE MA14+2 \ to skip the following, as only military lasers have \ any effect on the Constrictor or Cougar (or the Elite \ logo, should you ever bump into one of those out there \ in the black...) LSR LAS \ Divide the laser power of the current view by 4, so LSR LAS \ the damage inflicted on the super-ship is a quarter of \ the damage our military lasers would inflict on a \ normal ship .BURN LDA INWK+35 \ Fetch the hit ship's energy from byte #35 and subtract SEC \ our current laser power, and if the result is greater SBC LAS \ than zero, the other ship has survived the hit, so BCS MA14 \ jump down to MA14 ASL INWK+31 \ Set bit 7 of the ship byte #31 to indicate that it has SEC \ now been killed ROR INWK+31 LDA TYPE \ Did we just kill an asteroid? If not, jump to nosp, CMP #AST \ otherwise keep going BNE nosp LDA LAS \ Did we kill the asteroid using mining lasers? If not, CMP #Mlas \ jump to nosp, otherwise keep going BNE nosp JSR DORND \ Set A and X to random numbers LDX #SPL \ Set X to the ship type for a splinter AND #3 \ Reduce the random number in A to the range 0-3 JSR SPIN2 \ Call SPIN2 to spawn A items of type X (i.e. spawn \ 0-3 spliters) .nosp LDY #PLT \ Randomly spawn some alloy plates JSR SPIN LDY #OIL \ Randomly spawn some cargo canisters JSR SPIN JSR EXNO2 \ Call EXNO2 to process the fact that we have killed a \ ship (so increase the kill tally, make an explosion \ sound and so on) .MA14 STA INWK+35 \ Store the hit ship's updated energy in ship byte #35 LDA TYPE \ Call ANGRY to make this ship hostile, now that we JSR ANGRY \ have hit it
Name: Main flight loop (Part 12 of 16) [View individually] Type: Subroutine [Compare versions] Category: Main loop Summary: For each nearby ship: Draw the ship, remove if killed, loop back Deep dive: Program flow of the main game loop Drawing ships
The main flight loop covers most of the flight-specific aspects of Elite. This section covers the following: * Continue looping through all the ships in the local bubble, and for each one: * Draw the ship * Process removal of killed ships * Loop back up to MAL1 to move onto the next ship in the local bubble
.MA8 JSR LL9 \ Call LL9 to draw the ship we're processing on-screen .MA15 LDY #35 \ Fetch the ship's energy from byte #35 and copy it to LDA INWK+35 \ byte #35 in INF (so the ship's data in K% gets STA (INF),Y \ updated) LDA NEWB \ If bit 7 of the ship's NEWB flags is set, which means BMI KS1S \ the ship has docked or been scooped, jump to KS1S to \ skip the following, as we can't get a bounty for a \ ship that's no longer around LDA INWK+31 \ If bit 7 of the ship's byte #31 is clear, then the BPL MAC1 \ ship hasn't been killed by energy bomb, collision or \ laser fire, so jump to MAC1 to skip the following AND #%00100000 \ If bit 5 of the ship's byte #31 is clear then the BEQ MAC1 \ ship is no longer exploding, so jump to MAC1 to skip \ the following LDA NEWB \ Extract bit 6 of the ship's NEWB flags, so A = 64 if AND #%01000000 \ bit 6 is set, or 0 if it is clear. Bit 6 is set if \ this ship is a cop, so A = 64 if we just killed a \ policeman, otherwise it is 0 ORA FIST \ Update our FIST flag ("fugitive/innocent status") to STA FIST \ at least the value in A, which will instantly make us \ a fugitive if we just shot the sheriff, but won't \ affect our status if the enemy wasn't a copper LDA DLY \ If we already have an in-flight message on-screen (in ORA MJ \ which case DLY > 0), or we are in witchspace (in BNE KS1S \ which case MJ > 0), jump to KS1S to skip showing an \ on-screen bounty for this kill LDY #10 \ Fetch byte #10 of the ship's blueprint, which is the LDA (XX0),Y \ low byte of the bounty awarded when this ship is BEQ KS1S \ killed (in Cr * 10), and if it's zero jump to KS1S as \ there is no on-screen bounty to display TAX \ Put the low byte of the bounty into X INY \ Fetch byte #11 of the ship's blueprint, which is the LDA (XX0),Y \ high byte of the bounty awarded (in Cr * 10), and put TAY \ it into Y JSR MCASH \ Call MCASH to add (Y X) to the cash pot LDA #0 \ Print control code 0 (current cash, right-aligned to JSR MESS \ width 9, then " CR", newline) as an in-flight message .KS1S JMP KS1 \ Process the killing of this ship (which removes this \ ship from its slot and shuffles all the other ships \ down to close up the gap) .MAC1 LDA TYPE \ If the ship we are processing is a planet or sun, BMI MA27 \ jump to MA27 to skip the following two instructions JSR FAROF \ If the ship we are processing is a long way away (its BCC KS1S \ distance in any one direction is > 224, jump to KS1S \ to remove the ship from our local bubble, as it's just \ left the building .MA27 LDY #31 \ Fetch the ship's explosion/killed state from byte #31 LDA INWK+31 \ and copy it to byte #31 in INF (so the ship's data in STA (INF),Y \ K% gets updated) LDX XSAV \ We're done processing this ship, so fetch the ship's \ slot number, which we saved in XSAV back at the start \ of the loop INX \ Increment the slot number to move on to the next slot JMP MAL1 \ And jump back up to the beginning of the loop to get \ the next ship in the local bubble for processing
Name: Main flight loop (Part 13 of 16) [View individually] Type: Subroutine [Compare versions] Category: Main loop Summary: Show energy bomb effect, charge shields and energy banks Deep dive: Program flow of the main game loop Scheduling tasks with the main loop counter
The main flight loop covers most of the flight-specific aspects of Elite. This section covers the following: * Show energy bomb effect (if applicable) * Charge shields and energy banks (every 7 iterations of the main loop)
.MA18 LDA BOMB \ If we set off our energy bomb (see MA24 above), then BPL MA77 \ BOMB is now negative, so this skips to MA21 if our \ energy bomb is not going off ASL BOMB \ We set off our energy bomb, so rotate BOMB to the \ left by one place. BOMB was rotated left once already \ during this iteration of the main loop, back at MA24, \ so if this is the first pass it will already be \ %11111110, and this will shift it to %11111100 - so \ if we set off an energy bomb, it stays activated \ (BOMB > 0) for four iterations of the main loop JSR WSCAN \ Call WSCAN to wait for the vertical sync, so the whole \ screen gets drawn and the following palette change \ won't kick in while the screen is still refreshing LDA #DOFE21 \ Send a #DOFE21 %00110000 command to the I/O processor JSR OSWRCH \ to map logical colour 0 to physical colour 7 (white), LDA #%00110000 \ but with only one mapping (rather than the 7 JSR OSWRCH \ mappings required to do the mapping properly). This \ makes the space screen flash with coloured stripes. \ See p.382 of the Advanced User Guide for details of \ why this single palette change creates a special \ effect .MA77 LDA MCNT \ Fetch the main loop counter and calculate MCNT mod 7, AND #7 \ jumping to MA22 if it is non-zero (so the following BNE MA22 \ code only runs every 8 iterations of the main loop) LDX ENERGY \ Fetch our ship's energy levels and skip to b if bit 7 BPL b \ is not set, i.e. only charge the shields from the \ energy banks if they are at more than 50% charge LDX ASH \ Call SHD to recharge our aft shield and update the JSR SHD \ shield status in ASH STX ASH LDX FSH \ Call SHD to recharge our forward shield and update JSR SHD \ the shield status in FSH STX FSH .b SEC \ Set A = ENERGY + ENGY + 1, so our ship's energy LDA ENGY \ level goes up by 2 if we have an energy unit fitted, ADC ENERGY \ otherwise it goes up by 1 BCS P%+5 \ If the value of A did not overflow (the maximum STA ENERGY \ energy level is &FF), then store A in ENERGY
Name: Main flight loop (Part 14 of 16) [View individually] Type: Subroutine [Compare versions] Category: Main loop Summary: Spawn a space station if we are close enough to the planet Deep dive: Program flow of the main game loop Scheduling tasks with the main loop counter Ship data blocks
The main flight loop covers most of the flight-specific aspects of Elite. This section covers the following: * Spawn a space station if we are close enough to the planet (every 32 iterations of the main loop)
LDA MJ \ If we are in witchspace, jump down to MA23S to skip BNE MA23S \ the following, as there are no space stations in \ witchspace LDA MCNT \ Fetch the main loop counter and calculate MCNT mod 32, AND #31 \ jumping to MA93 if it is on-zero (so the following BNE MA93 \ code only runs every 32 iterations of the main loop LDA SSPR \ If we are inside the space station safe zone, jump to BNE MA23S \ MA23S to skip the following, as we already have a \ space station and don't need another TAY \ Set Y = A = 0 (A is 0 as we didn't branch with the \ previous BNE instruction) JSR MAS2 \ Call MAS2 to calculate the largest distance to the BNE MA23S \ planet in any of the three axes, and if it's \ non-zero, jump to MA23S to skip the following, as we \ are too far from the planet to bump into a space \ station \ We now want to spawn a space station, so first we \ need to set up a ship data block for the station in \ INWK that we can then pass to NWSPS to add a new \ station to our bubble of universe. We do this by \ copying the planet data block from K% to INWK so we \ can work on it, but we only need the first 29 bytes, \ as we don't need to worry about bytes #29 to #35 \ for planets (as they don't have rotation counters, \ AI, explosions, missiles, a ship line heap or energy \ levels) LDX #28 \ So we set a counter in X to copy 29 bytes from K%+0 \ to K%+28 .MAL4 LDA K%,X \ Load the X-th byte of K% and store in the X-th byte STA INWK,X \ of the INWK workspace DEX \ Decrement the loop counter BPL MAL4 \ Loop back for the next byte until we have copied the \ first 28 bytes of K% to INWK \ We now check the distance from our ship (at the \ origin) towards the planet's surface, by adding the \ planet's nosev vector to the planet's centre at \ (x, y, z) and checking our distance to the end \ point along the relevant axis INX \ Set X = 0 (as we ended the above loop with X as &FF) LDY #9 \ Call MAS1 with X = 0, Y = 9 to do the following: JSR MAS1 \ \ (x_sign x_hi x_lo) += (nosev_x_hi nosev_x_lo) * 2 \ \ A = |x_hi| BNE MA23S \ If A > 0, jump to MA23S to skip the following, as we \ are too far from the planet in the x-direction to \ bump into a space station LDX #3 \ Call MAS1 with X = 3, Y = 11 to do the following: LDY #11 \ JSR MAS1 \ (y_sign y_hi y_lo) += (nosev_y_hi nosev_y_lo) * 2 \ \ A = |y_hi| BNE MA23S \ If A > 0, jump to MA23S to skip the following, as we \ are too far from the planet in the y-direction to \ bump into a space station LDX #6 \ Call MAS1 with X = 6, Y = 13 to do the following: LDY #13 \ JSR MAS1 \ (z_sign z_hi z_lo) += (nosev_z_hi nosev_z_lo) * 2 \ \ A = |z_hi| BNE MA23S \ If A > 0, jump to MA23S to skip the following, as we \ are too far from the planet in the z-direction to \ bump into a space station LDA #192 \ Call FAROF2 to compare x_hi, y_hi and z_hi with 192, JSR FAROF2 \ which will set the C flag if all three are < 192, or \ clear the C flag if any of them are >= 192 BCC MA23S \ Jump to MA23S if any one of x_hi, y_hi or z_hi are \ >= 192 (i.e. they must all be < 192 for us to be near \ enough to the planet to bump into a space station) JSR WPLS \ Call WPLS to remove the sun from the screen, as we \ can't have both the sun and the space station at the \ same time JSR NWSPS \ Add a new space station to our local bubble of \ universe .MA23S JMP MA23 \ Jump to MA23 to skip the following planet and sun \ altitude checks
Name: Main flight loop (Part 15 of 16) [View individually] Type: Subroutine [Compare versions] Category: Main loop Summary: Perform altitude checks with the planet and sun and process fuel scooping if appropriate Deep dive: Program flow of the main game loop Scheduling tasks with the main loop counter
The main flight loop covers most of the flight-specific aspects of Elite. This section covers the following: * Perform an altitude check with the planet (every 32 iterations of the main loop, on iteration 10 of each 32) * Perform an an altitude check with the sun and process fuel scooping (every 32 iterations of the main loop, on iteration 20 of each 32)
.MA22 LDA MJ \ If we are in witchspace, jump down to MA23S to skip BNE MA23S \ the following, as there are no planets or suns to \ bump into in witchspace LDA MCNT \ Fetch the main loop counter and calculate MCNT mod 32, AND #31 \ which tells us the position of this loop in each block \ of 32 iterations .MA93 CMP #10 \ If this is the tenth iteration in this block of 32, BNE MA29 \ do the following, otherwise jump to MA29 to skip the \ planet altitude check and move on to the sun distance \ check IF _SNG45 OR _SOURCE_DISC LDA #50 \ If our energy bank status in ENERGY is >= 50, skip CMP ENERGY \ printing the following message (so the message is BCC P%+6 \ only shown if our energy is low) ASL A \ Print recursive token 100 ("ENERGY LOW{beep}") as an JSR MESS \ in-flight message ELIF _EXECUTIVE LDA #50 \ If our energy bank status in ENERGY is >= 50, skip CMP ENERGY \ printing the following message (so the message is BCC P%+11 \ only shown if our energy is low) ASL A \ Print recursive token 100 ("ENERGY LOW{beep}") as an JSR MESS \ in-flight message LDX #2 \ Call TALK with X = 2 to say "Energy low" using the JSR TALK \ Watford Electronics Beeb Speech Synthesiser (if one \ is fitted and speech has been enabled) ENDIF LDY #&FF \ Set our altitude in ALTIT to &FF, the maximum STY ALTIT INY \ Set Y = 0 JSR m \ Call m to calculate the maximum distance to the \ planet in any of the three axes, returned in A BNE MA23 \ If A > 0 then we are a fair distance away from the \ planet in at least one axis, so jump to MA23 to skip \ the rest of the altitude check JSR MAS3 \ Set A = x_hi^2 + y_hi^2 + z_hi^2, so using Pythagoras \ we now know that A now contains the square of the \ distance between our ship (at the origin) and the \ centre of the planet at (x_hi, y_hi, z_hi) BCS MA23 \ If the C flag was set by MAS3, then the result \ overflowed (was greater than &FF) and we are still a \ fair distance from the planet, so jump to MA23 as we \ haven't crashed into the planet SBC #36 \ Subtract 36 from x_hi^2 + y_hi^2 + z_hi^2. The radius \ of the planet is defined as 6 units and 6^2 = 36, so \ A now contains the high byte of our altitude above \ the planet surface, squared BCC MA28 \ If A < 0 then jump to MA28 as we have crashed into \ the planet STA R \ We are getting close to the planet, so we need to JSR LL5 \ work out how close. We know from the above that A \ contains our altitude squared, so we store A in R \ and call LL5 to calculate: \ \ Q = SQRT(R Q) = SQRT(A Q) \ \ Interestingly, Q doesn't appear to be set to 0 for \ this calculation, so presumably this doesn't make a \ difference LDA Q \ Store the result in ALTIT, our altitude STA ALTIT BNE MA23 \ If our altitude is non-zero then we haven't crashed, \ so jump to MA23 to skip to the next section .MA28 JMP DEATH \ If we get here then we just crashed into the planet \ or got too close to the sun, so jump to DEATH to start \ the funeral preparations and return from the main \ flight loop using a tail call .MA29 CMP #15 \ If this is the 15th iteration in this block of 32, BNE MA33 \ do the following, otherwise jump to MA33 to skip the \ docking computer manoeuvring LDA auto \ If auto is zero, then the docking computer is not BEQ MA23 \ activated, so jump to MA33 to skip the \ docking computer manoeuvring LDA #123 \ Set A = 123 and jump down to MA34 to print token 123 BNE MA34 \ ("DOCKING COMPUTERS ON") as an in-flight message .MA33 CMP #20 \ If this is the 20th iteration in this block of 32, BNE MA23 \ do the following, otherwise jump to MA23 to skip the \ sun altitude check LDA #30 \ Set CABTMP to 30, the cabin temperature in deep space STA CABTMP \ (i.e. one notch on the dashboard bar) LDA SSPR \ If we are inside the space station safe zone, jump to BNE MA23 \ MA23 to skip the following, as we can't have both the \ sun and space station at the same time, so we clearly \ can't be flying near the sun LDY #NI% \ Set Y to NI%, which is the offset in K% for the sun's \ data block, as the second block at K% is reserved for \ the sun (or space station) JSR MAS2 \ Call MAS2 to calculate the largest distance to the BNE MA23 \ sun in any of the three axes, and if it's non-zero, \ jump to MA23 to skip the following, as we are too far \ from the sun for scooping or temperature changes JSR MAS3 \ Set A = x_hi^2 + y_hi^2 + z_hi^2, so using Pythagoras \ we now know that A now contains the square of the \ distance between our ship (at the origin) and the \ heart of the sun at (x_hi, y_hi, z_hi) EOR #%11111111 \ Invert A, so A is now small if we are far from the \ sun and large if we are close to the sun, in the \ range 0 = far away to &FF = extremely close, ouch, \ hot, hot, hot! ADC #30 \ Add the minimum cabin temperature of 30, so we get \ one of the following: \ \ * If the C flag is clear, A contains the cabin \ temperature, ranging from 30 to 255, that's hotter \ the closer we are to the sun \ \ * If the C flag is set, the addition has rolled over \ and the cabin temperature is over 255 STA CABTMP \ Store the updated cabin temperature BCS MA28 \ If the C flag is set then jump to MA28 to die, as \ our temperature is off the scale CMP #&E0 \ If the cabin temperature < 224 then jump to MA23 to BCC MA23 \ to skip fuel scooping, as we aren't close enough LDA BST \ If we don't have fuel scoops fitted, jump to BA23 to BEQ MA23 \ skip fuel scooping, as we can't scoop without fuel \ scoops LDA DELT4+1 \ We are now successfully fuel scooping, so it's time LSR A \ to work out how much fuel we're scooping. Fetch the \ high byte of DELT4, which contains our current speed \ divided by 4, and halve it to get our current speed \ divided by 8 (so it's now a value between 1 and 5, as \ our speed is normally between 1 and 40). This gives \ us the amount of fuel that's being scooped in A, so \ the faster we go, the more fuel we scoop, and because \ the fuel levels are stored as 10 * the fuel in light \ years, that means we just scooped between 0.1 and 0.5 \ light years of free fuel ADC QQ14 \ Set A = A + the current fuel level * 10 (from QQ14) CMP #70 \ If A > 70 then set A = 70 (as 70 is the maximum fuel BCC P%+4 \ level, or 7.0 light years) LDA #70 STA QQ14 \ Store the updated fuel level in QQ14 LDA #160 \ Set A to token 160 ("FUEL SCOOPS ON") .MA34 JSR MESS \ Print the token in A as an in-flight message
Name: Main flight loop (Part 16 of 16) [View individually] Type: Subroutine [Compare versions] Category: Main loop Summary: Process laser pulsing, E.C.M. energy drain, call stardust routine Deep dive: Program flow of the main game loop
The main flight loop covers most of the flight-specific aspects of Elite. This section covers the following: * Process laser pulsing * Process E.C.M. energy drain * Jump to the stardust routine if we are in a space view * Return from the main flight loop
.MA23 LDA LAS2 \ If the current view has no laser, jump to MA16 to skip BEQ MA16 \ the following LDA LASCT \ If LASCT >= 8, jump to MA16 to skip the following, so CMP #8 \ for a pulse laser with a LASCT between 8 and 10, the BCS MA16 \ the laser stays on, but for a LASCT of 7 or less it \ gets turned off and stays off until LASCT reaches zero \ and the next pulse can start (if the fire button is \ still being pressed) \ \ For pulse lasers, LASCT gets set to 10 in ma1 above, \ and it decrements every vertical sync (50 times a \ second), so this means it pulses five times a second, \ with the laser being on for the first 3/10 of each \ pulse and off for the rest of the pulse \ \ If this is a beam laser, LASCT is 0 so we always keep \ going here. This means the laser doesn't pulse, but it \ does get drawn and removed every cycle, in a slightly \ different place each time, so the beams still flicker \ around the screen JSR LASLI2 \ Redraw the existing laser lines, which has the effect \ of removing them from the screen LDA #0 \ Set LAS2 to 0 so if this is a pulse laser, it will STA LAS2 \ skip over the above until the next pulse (this has no \ effect if this is a beam laser) .MA16 LDA ECMP \ If our E.C.M is not on, skip to MA69, otherwise keep BEQ MA69 \ going to drain some energy JSR DENGY \ Call DENGY to deplete our energy banks by 1 BEQ MA70 \ If we have no energy left, jump to MA70 to turn our \ E.C.M. off .MA69 LDA ECMA \ If an E.C.M is going off (our's or an opponent's) then BEQ MA66 \ keep going, otherwise skip to MA66 DEC ECMA \ Decrement the E.C.M. countdown timer, and if it has BNE MA66 \ reached zero, keep going, otherwise skip to MA66 .MA70 JSR ECMOF \ If we get here then either we have either run out of \ energy, or the E.C.M. timer has run down, so switch \ off the E.C.M. .MA66 LDA QQ11 \ If this is not a space view (i.e. QQ11 is non-zero) BNE oh \ then jump to oh to return from the main flight loop \ (as oh is an RTS) JSR STARS \ This is a space view, so call the STARS routine to \ process the stardust JMP PBFL \ And call PBFL to ask the I/O processor to draw the \ dust particles, returning from the main flight loop \ using a tail call
Name: SPIN [View individually] Type: Subroutine [Compare versions] Category: Universe Summary: Randomly spawn cargo from a destroyed ship
Arguments: Y The type of cargo to consider spawning (typically #PLT or #OIL) Other entry points: oh Contains an RTS SPIN2 Remove any randomness: spawn cargo of a specific type (given in X), and always spawn the number given in A
.SPIN JSR DORND \ Fetch a random number, and jump to oh if it is BPL oh \ positive (50% chance) TYA \ Copy the cargo type from Y into A and X TAX LDY #0 \ Fetch the first byte of the hit ship's blueprint, AND (XX0),Y \ which determines the maximum number of bits of \ debris shown when the ship is destroyed, and AND \ with the random number we just fetched AND #15 \ Reduce the random number in A to the range 0-15 .SPIN2 STA CNT \ Store the result in CNT, so CNT contains a random \ number between 0 and the maximum number of bits of \ debris that this ship will release when destroyed \ (to a maximum of 15 bits of debris) .spl BEQ oh \ We're going to go round a loop using CNT as a counter \ so this checks whether the counter is zero and jumps \ to oh when it gets there (which might be straight \ away) LDA #0 \ Call SFS1 to spawn the specified cargo from the now JSR SFS1 \ deceased parent ship, giving the spawned canister an \ AI flag of 0 (no AI, no E.C.M., non-hostile) DEC CNT \ Decrease the loop counter BNE spl+2 \ Jump back up to the LDA &0 instruction above (this BPL \ is effectively a JMP as CNT will never be negative) .oh RTS \ Return from the subroutine
Name: MT27 [View individually] Type: Subroutine [Compare versions] Category: Text Summary: Print the captain's name during mission briefings Deep dive: Extended text tokens
This routine prints the following tokens, depending on the galaxy number: * Token 217 ("CURRUTHERS") in galaxy 0 * Token 218 ("FOSDYKE SMYTHE") in galaxy 1 * Token 219 ("FORTESQUE") in galaxy 2 This is used when printing extended token 213 as part of the mission briefings, which looks like this when printed: Commander {commander name}, I am Captain {mission captain's name} of Her Majesty's Space Navy where {mission captain's name} is replaced by one of the names above.
.MT27 LDA #217 \ Set A = 217, so when we fall through into MT28, the \ 217 gets added to the current galaxy number, so the \ extended token that is printed is 217-219 (as this is \ only called in galaxies 0 through 2) EQUB &2C \ Skip the next instruction by turning it into \ &2C &A9 &DC, or BIT &DCA9, which does nothing apart \ from affect the flags
Name: MT28 [View individually] Type: Subroutine Category: Text Summary: Print the location hint during the mission 1 briefing Deep dive: Extended text tokens
This routine prints the following tokens, depending on the galaxy number: * Token 220 ("WAS LAST SEEN AT {single cap}REESDICE") in galaxy 0 * Token 221 ("IS BELIEVED TO HAVE JUMPED TO THIS GALAXY") in galaxy 1 This is used when printing extended token 10 as part of the mission 1 briefing, which looks like this when printed: It went missing from our ship yard on Xeer five months ago and {mission 1 location hint} where {mission 1 location hint} is replaced by one of the names above.
.MT28 LDA #220 \ Set A = galaxy number in GCNT + 220, which is in the CLC \ range 220-221, as this is only called in galaxies 0 ADC GCNT \ and 1 BNE DETOK \ Jump to DETOK to print extended token 220-221, \ returning from the subroutine using a tail call (this \ BNE is effectively a JMP as A is never zero)
Name: DETOK3 [View individually] Type: Subroutine Category: Text Summary: Print an extended recursive token from the RUTOK token table Deep dive: Extended system descriptions Extended text tokens
Arguments: A The recursive token to be printed, in the range 0-255 Returns: A A is preserved Y Y is preserved V(1 0) V(1 0) is preserved
.DETOK3 PHA \ Store A on the stack, so we can retrieve it later TAX \ Copy the token number from A into X TYA \ Store Y on the stack PHA LDA V \ Store V(1 0) on the stack PHA LDA V+1 PHA LDA #LO(RUTOK) \ Set V to the low byte of RUTOK STA V LDA #HI(RUTOK) \ Set A to the high byte of RUTOK BNE DTEN \ Call DTEN to print token number X from the RUTOK \ table and restore the values of A, Y and V(1 0) from \ the stack, returning from the subroutine using a tail \ call (this BNE is effectively a JMP as A is never \ zero)
Name: DETOK [View individually] Type: Subroutine Category: Text Summary: Print an extended recursive token from the TKN1 token table Deep dive: Extended text tokens
Arguments: A The recursive token to be printed, in the range 1-255 Returns: A A is preserved Y Y is preserved V(1 0) V(1 0) is preserved Other entry points: DTEN Print recursive token number X from the token table pointed to by (A V), used to print tokens from the RUTOK table via calls to DETOK3
.DETOK PHA \ Store A on the stack, so we can retrieve it later TAX \ Copy the token number from A into X TYA \ Store Y on the stack PHA LDA V \ Store V(1 0) on the stack PHA LDA V+1 PHA LDA #LO(TKN1) \ Set V to the low byte of TKN1 STA V LDA #HI(TKN1) \ Set A to the high byte of TKN1, so when we fall \ through into DTEN, V(1 0) gets set to the address of \ the TKN1 token table .DTEN STA V+1 \ Set the high byte of V(1 0) to A, so V(1 0) now points \ to the start of the token table to use LDY #0 \ First, we need to work our way through the table until \ we get to the token that we want to print. Tokens are \ delimited by #VE, and VE EOR VE = 0, so we work our \ way through the table in, counting #VE delimiters \ until we have passed X of them, at which point we jump \ down to DTL2 to do the actual printing. So first, we \ set a counter Y to point to the character offset as we \ scan through the table .DTL1 LDA (V),Y \ Load the character at offset Y in the token table, \ which is the next character from the token table EOR #VE \ Tokens are stored in memory having been EOR'd with \ #VE, so we repeat the EOR to get the actual character \ in this token BNE DT1 \ If the result is non-zero, then this is a character \ in a token rather than the delimiter (which is #VE), \ so jump to DT1 DEX \ We have just scanned the end of a token, so decrement \ X, which contains the token number we are looking for BEQ DTL2 \ If X has now reached zero then we have found the token \ we are looking for, so jump down to DTL2 to print it .DT1 INY \ Otherwise this isn't the token we are looking for, so \ increment the character pointer BNE DTL1 \ If Y hasn't just wrapped around to 0, loop back to \ DTL1 to process the next character INC V+1 \ We have just crossed into a new page, so increment \ V+1 so that V points to the start of the new page BNE DTL1 \ Jump back to DTL1 to process the next character (this \ BNE is effectively a JMP as V+1 won't reach zero \ before we reach the end of the token table) .DTL2 INY \ We just detected the delimiter byte before the token \ that we want to print, so increment the character \ pointer to point to the first character of the token, \ rather than the delimiter BNE P%+4 \ If Y hasn't just wrapped around to 0, skip the next \ instruction INC V+1 \ We have just crossed into a new page, so increment \ V+1 so that V points to the start of the new page LDA (V),Y \ Load the character at offset Y in the token table, \ which is the next character from the token we want to \ print EOR #VE \ Tokens are stored in memory having been EOR'd with \ #VE, so we repeat the EOR to get the actual character \ in this token BEQ DTEX \ If the result is zero, then this is the delimiter at \ the end of the token to print (which is #VE), so jump \ to DTEX to return from the subroutine, as we are done \ printing JSR DETOK2 \ Otherwise call DETOK2 to print this part of the token JMP DTL2 \ Jump back to DTL2 to process the next character .DTEX PLA \ Restore V(1 0) from the stack, so it is preserved STA V+1 \ through calls to this routine PLA STA V PLA \ Restore Y from the stack, so it is preserved through TAY \ calls to this routine PLA \ Restore A from the stack, so it is preserved through \ calls to this routine RTS \ Return from the subroutine
Name: DETOK2 [View individually] Type: Subroutine Category: Text Summary: Print an extended text token (1-255) Deep dive: Extended text tokens
Arguments: A The token to be printed (1-255) Returns: A A is preserved Y Y is preserved V(1 0) V(1 0) is preserved Other entry points: DTS Print the single letter pointed to by A, where A is an address within the extended two-letter token tables of TKN2 and QQ16
.DETOK2 CMP #32 \ If A < 32 then this is a jump token, so skip to DT3 to BCC DT3 \ process it BIT DTW3 \ If bit 7 of DTW3 is clear, then extended tokens are BPL DT8 \ enabled, so jump to DT8 to process them \ If we get there then this is not a jump token and \ extended tokens are not enabled, so we can call the \ standard text token routine at TT27 to print the token TAX \ Copy the token number from A into X TYA \ Store Y on the stack PHA LDA V \ Store V(1 0) on the stack PHA LDA V+1 PHA TXA \ Copy the token number from X back into A JSR TT27 \ Call TT27 to print the text token JMP DT7 \ Jump to DT7 to restore V(1 0) and Y from the stack and \ return from the subroutine .DT8 \ If we get here then this is not a jump token and \ extended tokens are enabled CMP #'[' \ If A < ASCII "[" (i.e. A <= ASCII "Z", or 90) then BCC DTS \ this is a printable ASCII character, so jump down to \ DTS to print it CMP #129 \ If A < 129, so A is in the range 91-128, jump down to BCC DT6 \ DT6 to print a randomised token from the MTIN table CMP #215 \ If A < 215, so A is in the range 129-214, jump to BCC DETOK \ DETOK as this is a recursive token, returning from the \ subroutine using a tail call \ If we get here then A >= 215, so this is a two-letter \ token from the extended TKN2/QQ16 table SBC #215 \ Subtract 215 to get a token number in the range 0-12 \ (the C flag is set as we passed through the BCC above, \ so this subtraction is correct) ASL A \ Set A = A * 2, so it can be used as a pointer into the \ two-letter token tables at TKN2 and QQ16 PHA \ Store A on the stack, so we can restore it for the \ second letter below TAX \ Fetch the first letter of the two-letter token from LDA TKN2,X \ TKN2, which is at TKN2 + X JSR DTS \ Call DTS to print it PLA \ Restore A from the stack and transfer it into X TAX LDA TKN2+1,X \ Fetch the second letter of the two-letter token from \ TKN2, which is at TKN2 + X + 1, and fall through into \ DTS to print it .DTS CMP #'A' \ If A < ASCII "A", jump to DT9 to print this as ASCII BCC DT9 BIT DTW6 \ If bit 7 of DTW6 is set, then lower case has been BMI DT10 \ enabled by jump token 13, {lower case}, so jump to \ DT10 to apply the lower case and single cap masks BIT DTW2 \ If bit 7 of DTW2 is set, then we are not currently BMI DT5 \ printing a word, so jump to DT5 so we skip the setting \ of lower case in Sentence Case (which we only want to \ do when we are already printing a word) .DT10 ORA DTW1 \ Convert the character to lower case if DTW1 is \ %00100000 (i.e. if we are in {sentence case} mode) .DT5 AND DTW8 \ Convert the character to upper case if DTW8 is \ %11011111 (i.e. after a {single cap} token) .DT9 JMP DASC \ Jump to DASC to print the ASCII character in A, \ returning from the routine using a tail call .DT3 \ If we get here then the token number in A is in the \ range 1 to 32, so this is a jump token that should \ call the corresponding address in the jump table at \ JMTB TAX \ Copy the token number from A into X TYA \ Store Y on the stack PHA LDA V \ Store V(1 0) on the stack PHA LDA V+1 PHA TXA \ Copy the token number from X back into A ASL A \ Set A = A * 2, so it can be used as a pointer into the \ jump table at JMTB, though because the original range \ of values is 1-32, so the doubled range is 2-64, we \ need to take the offset into the jump table from \ JMTB-2 rather than JMTB TAX \ Copy the doubled token number from A into X LDA JMTB-2,X \ Set DTM(2 1) to the X-th address from the table at STA DTM+1 \ JTM-2, which modifies the JSR DASC instruction at LDA JMTB-1,X \ label DTM below so that it calls the subroutine at the STA DTM+2 \ relevant address from the JMTB table TXA \ Copy the doubled token number from X back into A LSR A \ Halve A to get the original token number .DTM JSR DASC \ Call the relevant JMTB subroutine, as this instruction \ will have been modified by the above to point to the \ relevant address .DT7 PLA \ Restore V(1 0) from the stack, so it is preserved STA V+1 \ through calls to this routine PLA STA V PLA \ Restore Y from the stack, so it is preserved through TAY \ calls to this routine RTS \ Return from the subroutine .DT6 \ If we get here then the token number in A is in the \ range 91-128, which means we print a randomly picked \ token from the token range given in the corresponding \ entry in the MTIN table STA SC \ Store the token number in SC TYA \ Store Y on the stack PHA LDA V \ Store V(1 0) on the stack PHA LDA V+1 PHA JSR DORND \ Set X to a random number TAX LDA #0 \ Set A to 0, so we can build a random number from 0 to \ 4 in A plus the C flag, with each number being equally \ likely CPX #51 \ Add 1 to A if X >= 51 ADC #0 CPX #102 \ Add 1 to A if X >= 102 ADC #0 CPX #153 \ Add 1 to A if X >= 153 ADC #0 CPX #204 \ Set the C flag if X >= 204 LDX SC \ Fetch the token number from SC into X, so X is now in \ the range 91-128 ADC MTIN-91,X \ Set A = MTIN-91 + token number (91-128) + random (0-4) \ = MTIN + token number (0-37) + random (0-4) JSR DETOK \ Call DETOK to print the extended recursive token in A JMP DT7 \ Jump to DT7 to restore V(1 0) and Y from the stack and \ return from the subroutine using a tail call
Name: Firebird [View individually] Type: Variable [Compare versions] Category: Copy protection Summary: The name "Firebird", buried in the code of the Executive version
IF _EXECUTIVE EQUS "Firebird" EQUB 13 ENDIF
Name: MT1 [View individually] Type: Subroutine Category: Text Summary: Switch to ALL CAPS when printing extended tokens Deep dive: Extended text tokens
This routine sets the following: * DTW1 = %00000000 (do not change case to lower case) * DTW6 = %00000000 (lower case is not enabled)
.MT1 LDA #%00000000 \ Set A = %00000000, so when we fall through into MT2, \ both DTW1 and DTW6 get set to %00000000 EQUB &2C \ Skip the next instruction by turning it into \ &2C &A9 &20, or BIT &20A9, which does nothing apart \ from affect the flags
Name: MT2 [View individually] Type: Subroutine Category: Text Summary: Switch to Sentence Case when printing extended tokens Deep dive: Extended text tokens
This routine sets the following: * DTW1 = %00100000 (apply lower case to the second letter of a word onwards) * DTW6 = %00000000 (lower case is not enabled)
.MT2 LDA #%00100000 \ Set DTW1 = %00100000 STA DTW1 LDA #00000000 \ Set DTW6 = %00000000 STA DTW6 RTS \ Return from the subroutine
Name: MT8 [View individually] Type: Subroutine [Compare versions] Category: Text Summary: Tab to column 6 and start a new word when printing extended tokens Deep dive: Extended text tokens
This routine sets the following: * XC = 6 (tab to column 6) * DTW2 = %11111111 (we are not currently printing a word)
.MT8 LDA #6 \ Move the text cursor to column 6 JSR DOXC LDA #%11111111 \ Set all the bits in DTW2 STA DTW2 RTS \ Return from the subroutine
Name: MT9 [View individually] Type: Subroutine [Compare versions] Category: Text Summary: Clear the screen and set the current view type to 1 Deep dive: Extended text tokens
This routine sets the following: * XC = 1 (tab to column 1) before calling TT66 to clear the screen and set the view type to 1.
.MT9 LDA #1 \ Call DOXC to move the text cursor to column 1 JSR DOXC JMP TT66 \ Jump to TT66 to clear the screen and set the current \ view type to 1, returning from the subroutine using a \ tail call
Name: MT13 [View individually] Type: Subroutine Category: Text Summary: Switch to lower case when printing extended tokens Deep dive: Extended text tokens
This routine sets the following: * DTW1 = %00100000 (apply lower case to the second letter of a word onwards) * DTW6 = %10000000 (lower case is enabled)
.MT13 LDA #%10000000 \ Set DTW6 = %10000000 STA DTW6 LDA #%00100000 \ Set DTW1 = %00100000 STA DTW1 RTS \ Return from the subroutine
Name: MT6 [View individually] Type: Subroutine Category: Text Summary: Switch to standard tokens in Sentence Case Deep dive: Extended text tokens
This routine sets the following: * QQ17 = %10000000 (set Sentence Case for standard tokens) * DTW3 = %11111111 (print standard tokens)
.MT6 LDA #%10000000 \ Set bit 7 of QQ17 to switch standard tokens to STA QQ17 \ Sentence Case LDA #%11111111 \ Set A = %11111111, so when we fall through into MT5, \ DTW3 gets set to %11111111 and calls to DETOK print \ standard tokens EQUB &2C \ Skip the next instruction by turning it into \ &2C &A9 &00, or BIT &00A9, which does nothing apart \ from affect the flags
Name: MT5 [View individually] Type: Subroutine Category: Text Summary: Switch to extended tokens Deep dive: Extended text tokens
This routine sets the following: * DTW3 = %00000000 (print extended tokens)
.MT5 LDA #%00000000 \ Set DTW3 = %00000000, so that calls to DETOK print STA DTW3 \ extended tokens RTS \ Return from the subroutine
Name: MT14 [View individually] Type: Subroutine Category: Text Summary: Switch to justified text when printing extended tokens Deep dive: Extended text tokens
This routine sets the following: * DTW4 = %10000000 (justify text, print buffer on carriage return) * DTW5 = 0 (reset line buffer size)
.MT14 LDA #%10000000 \ Set A = %10000000, so when we fall through into MT15, \ DTW4 gets set to %10000000 EQUB &2C \ Skip the next instruction by turning it into \ &2C &A9 &00, or BIT &00A9, which does nothing apart \ from affect the flags
Name: MT15 [View individually] Type: Subroutine Category: Text Summary: Switch to left-aligned text when printing extended tokens Deep dive: Extended text tokens
This routine sets the following: * DTW4 = %00000000 (do not justify text, print buffer on carriage return) * DTW5 = 0 (reset line buffer size)
.MT15 LDA #0 \ Set DTW4 = %00000000 STA DTW4 ASL A \ Set DTW5 = 0 (even when we fall through from MT14 with STA DTW5 \ A set to %10000000) RTS \ Return from the subroutine
Name: MT17 [View individually] Type: Subroutine Category: Text Summary: Print the selected system's adjective, e.g. Lavian for Lave Deep dive: Extended text tokens
The adjective for the current system is generated by taking the system name, removing the last character if it is a vowel, and adding "-ian" to the end, so: * Lave gives Lavian (as in "Lavian tree grub") * Leesti gives Leestian (as in "Leestian Evil Juice") This routine is called by jump token 17, {system name adjective}, and it can only be used when justified text is being printed - i.e. following jump token 14, {justify} - because the routine needs to use the line buffer to work.
.MT17 LDA QQ17 \ Set QQ17 = %10111111 to switch to Sentence Case AND #%10111111 STA QQ17 LDA #3 \ Print control code 3 (selected system name) into the JSR TT27 \ line buffer LDX DTW5 \ Load the last character of the line buffer BUF into A LDA BUF-1,X \ (as DTW5 contains the buffer size, so character DTW5-1 \ is the last character in the buffer BUF) JSR VOWEL \ Test whether the character is a vowel, in which case \ this will set the C flag BCC MT171 \ If the character is not a vowel, skip the following \ instruction DEC DTW5 \ The character is a vowel, so decrement DTW5, which \ removes the last character from the line buffer (i.e. \ it removes the trailing vowel from the system name) .MT171 LDA #153 \ Print extended token 153 ("IAN"), returning from the JMP DETOK \ subroutine using a tail call
Name: MT18 [View individually] Type: Subroutine Category: Text Summary: Print a random 1-8 letter word in Sentence Case Deep dive: Extended text tokens
.MT18 JSR MT19 \ Call MT19 to capitalise the next letter (i.e. set \ Sentence Case for this word only) JSR DORND \ Set A and X to random numbers and reduce A to a AND #3 \ random number in the range 0-3 TAY \ Copy the random number into Y, so we can use Y as a \ loop counter to print 1-4 words (i.e. Y+1 words) .MT18L JSR DORND \ Set A and X to random numbers and reduce A to an even AND #62 \ random number in the range 0-62 (as bit 0 of 62 is 0) TAX \ Copy the random number into X, so X contains the table \ offset of a random extended two-letter token from 0-31 \ which we can now use to pick a token from the combined \ tables at TKN2+2 and QQ16 (we intentionally exclude \ the first token in TKN2, which contains a newline) LDA TKN2+2,X \ Print the first letter of the token at TKN2+2 + X JSR DTS LDA TKN2+3,X \ Print the second letter of the token at TKN2+2 + X JSR DTS DEY \ Decrement the loop counter BPL MT18L \ Loop back to MT18L to print another two-letter token \ until we have printed Y+1 of them RTS \ Return from the subroutine
Name: MT19 [View individually] Type: Subroutine Category: Text Summary: Capitalise the next letter Deep dive: Extended text tokens
This routine sets the following: * DTW8 = %11011111 (capitalise the next letter)
.MT19 LDA #%11011111 \ Set DTW8 = %11011111 STA DTW8 RTS \ Return from the subroutine
Name: VOWEL [View individually] Type: Subroutine Category: Text Summary: Test whether a character is a vowel
Arguments: A The character to be tested Returns: C flag The C flag is set if the character is a vowel, otherwise it is clear
.VOWEL ORA #%00100000 \ Set bit 5 of the character to make it lower case CMP #'a' \ If the letter is a vowel, jump to VRTS to return from BEQ VRTS \ the subroutine with the C flag set (as the CMP will CMP #'e' \ set the C flag if the comparison is equal) BEQ VRTS CMP #'i' BEQ VRTS CMP #'o' BEQ VRTS CMP #'u' BEQ VRTS CLC \ The character is not a vowel, so clear the C flag .VRTS RTS \ Return from the subroutine
Name: WHITETEXT [View individually] Type: Subroutine Category: Text Summary: Switch to white text
.WHITETEXT LDA #32 \ Send a #SETVDU19 32 command to the I/O processor to JSR DOVDU19 \ switch to the mode 1 palette for the title screen, \ which is yellow (colour 1), white (colour 2) and cyan \ (colour 3) LDA #RED \ Send a #SETCOL RED command to the I/O processor to JMP DOCOL \ switch to colour 2, which is white in the title \ screen, and return from the subroutine using a tail \ call
Name: JMTB [View individually] Type: Variable [Compare versions] Category: Text Summary: The extended token table for jump tokens 1-32 (DETOK) Deep dive: Extended text tokens
.JMTB EQUW MT1 \ Token 1: Switch to ALL CAPS EQUW MT2 \ Token 2: Switch to Sentence Case EQUW TT27 \ Token 3: Print the selected system name EQUW TT27 \ Token 4: Print the commander's name EQUW MT5 \ Token 5: Switch to extended tokens EQUW MT6 \ Token 6: Switch to standard tokens, in Sentence Case EQUW DASC \ Token 7: Beep EQUW MT8 \ Token 8: Tab to column 6 EQUW MT9 \ Token 9: Clear screen, tab to column 1, view type = 1 EQUW DASC \ Token 10: Line feed EQUW NLIN4 \ Token 11: Draw box around title (line at pixel row 19) EQUW DASC \ Token 12: Carriage return EQUW MT13 \ Token 13: Switch to lower case EQUW MT14 \ Token 14: Switch to justified text EQUW MT15 \ Token 15: Switch to left-aligned text EQUW MT16 \ Token 16: Print the character in DTW7 (drive number) EQUW MT17 \ Token 17: Print system name adjective in Sentence Case EQUW MT18 \ Token 18: Randomly print 1 to 4 two-letter tokens EQUW MT19 \ Token 19: Capitalise first letter of next word only EQUW DASC \ Token 20: Unused EQUW CLYNS \ Token 21: Clear the bottom few lines of the space view EQUW PAUSE \ Token 22: Display ship and wait for key press EQUW MT23 \ Token 23: Move to row 10, white text, set lower case EQUW PAUSE2 \ Token 24: Wait for a key press EQUW BRIS \ Token 25: Show incoming message screen, wait 2 seconds EQUW MT26 \ Token 26: Fetch line input from keyboard (filename) EQUW MT27 \ Token 27: Print mission captain's name (217-219) EQUW MT28 \ Token 28: Print mission 1 location hint (220-221) EQUW MT29 \ Token 29: Column 6, white text, lower case in words EQUW WHITETEXT \ Token 30: White text EQUW DASC \ Token 31: Unused EQUW DASC \ Token 32: Unused
Name: TKN2 [View individually] Type: Variable Category: Text Summary: The extended two-letter token lookup table Deep dive: Extended text tokens
Two-letter token lookup table for extended tokens 215-227.
.TKN2 EQUB 12, 10 \ Token 215 = {crlf} EQUS "AB" \ Token 216 EQUS "OU" \ Token 217 EQUS "SE" \ Token 218 EQUS "IT" \ Token 219 EQUS "IL" \ Token 220 EQUS "ET" \ Token 221 EQUS "ST" \ Token 222 EQUS "ON" \ Token 223 EQUS "LO" \ Token 224 EQUS "NU" \ Token 225 EQUS "TH" \ Token 226 EQUS "NO" \ Token 227
Name: QQ16 [View individually] Type: Variable [Compare versions] Category: Text Summary: The two-letter token lookup table Deep dive: Printing text tokens
Two-letter token lookup table for tokens 128-159. See the deep dive on "Printing text tokens" for details of how the two-letter token system works. These two-letter tokens can also be used in the extended text token system, by adding 100 to the token number. So the extended two-letter token 228 is "AL", the same as the standard two-letter token 128. In this system, the last four tokens are not available, as they would have numbers greater than 255.
.QQ16 EQUS "AL" \ Token 128 EQUS "LE" \ Token 129 EQUS "XE" \ Token 130 EQUS "GE" \ Token 131 EQUS "ZA" \ Token 132 EQUS "CE" \ Token 133 EQUS "BI" \ Token 134 EQUS "SO" \ Token 135 EQUS "US" \ Token 136 EQUS "ES" \ Token 137 EQUS "AR" \ Token 138 EQUS "MA" \ Token 139 EQUS "IN" \ Token 140 EQUS "DI" \ Token 141 EQUS "RE" \ Token 142 EQUS "A?" \ Token 143 EQUS "ER" \ Token 144 EQUS "AT" \ Token 145 EQUS "EN" \ Token 146 EQUS "BE" \ Token 147 EQUS "RA" \ Token 148 EQUS "LA" \ Token 149 EQUS "VE" \ Token 150 EQUS "TI" \ Token 151 EQUS "ED" \ Token 152 EQUS "OR" \ Token 153 EQUS "QU" \ Token 154 EQUS "AN" \ Token 155 EQUS "TE" \ Token 156 EQUS "IS" \ Token 157 EQUS "RI" \ Token 158 EQUS "ON" \ Token 159
Name: shpcol [View individually] Type: Variable Category: Drawing ships Summary: Ship colours
.shpcol EQUB 0 EQUB YELLOW \ Missile EQUB CYAN \ Coriolis space station EQUB CYAN \ Escape pod EQUB CYAN \ Alloy plate EQUB CYAN \ Cargo canister EQUB RED \ Boulder EQUB RED \ Asteroid EQUB RED \ Splinter EQUB CYAN \ Shuttle EQUB CYAN \ Transporter EQUB CYAN \ Cobra Mk III EQUB CYAN \ Python EQUB CYAN \ Boa EQUB CYAN \ Anaconda EQUB RED \ Rock hermit (asteroid) EQUB CYAN \ Viper EQUB CYAN \ Sidewinder EQUB CYAN \ Mamba EQUB CYAN \ Krait EQUB CYAN \ Adder EQUB CYAN \ Gecko EQUB CYAN \ Cobra Mk I EQUB CYAN \ Worm EQUB CYAN \ Cobra Mk III (pirate) EQUB CYAN \ Asp Mk II EQUB CYAN \ Python (pirate) EQUB CYAN \ Fer-de-lance EQUB %11001001 \ Moray (colour 3, 2, 0, 1 = cyan/red/black/yellow) EQUB WHITE \ Thargoid EQUB WHITE \ Thargon EQUB CYAN \ Constrictor EQUB CYAN \ The Elite logo EQUB CYAN \ Cougar
Name: scacol [View individually] Type: Variable Category: Drawing ships Summary: Ship colours on the scanner
.scacol EQUB 0 EQUB YELLOW2 \ Missile EQUB GREEN2 \ Coriolis space station EQUB BLUE2 \ Escape pod EQUB BLUE2 \ Alloy plate EQUB BLUE2 \ Cargo canister EQUB RED2 \ Boulder EQUB RED2 \ Asteroid EQUB RED2 \ Splinter EQUB CYAN2 \ Shuttle EQUB CYAN2 \ Transporter EQUB CYAN2 \ Cobra Mk III EQUB MAG2 \ Python EQUB MAG2 \ Boa EQUB MAG2 \ Anaconda EQUB RED2 \ Rock hermit (asteroid) EQUB CYAN2 \ Viper EQUB CYAN2 \ Sidewinder EQUB CYAN2 \ Mamba EQUB CYAN2 \ Krait EQUB CYAN2 \ Adder EQUB CYAN2 \ Gecko EQUB CYAN2 \ Cobra Mk I EQUB BLUE2 \ Worm EQUB CYAN2 \ Cobra Mk III (pirate) EQUB CYAN2 \ Asp Mk II EQUB MAG2 \ Python (pirate) EQUB CYAN2 \ Fer-de-lance EQUB CYAN2 \ Moray EQUB WHITE2 \ Thargoid EQUB CYAN2 \ Thargon EQUB CYAN2 \ Constrictor EQUB 0 \ The Elite logo EQUB CYAN2 \ Cougar EQUD 0
Name: LSX2 [View individually] Type: Variable [Compare versions] Category: Drawing lines Summary: The ball line heap for storing x-coordinates Deep dive: The ball line heap
.LSX2 SKIP 256 \ The ball line heap for storing x-coordinates (see the \ deep dive on "The ball line heap" for details)
Name: LSY2 [View individually] Type: Variable [Compare versions] Category: Drawing lines Summary: The ball line heap for storing y-coordinates Deep dive: The ball line heap
.LSY2 SKIP 256 \ The ball line heap for storing y-coordinates (see the \ deep dive on "The ball line heap" for details)
Save output/ELTA.bin
PRINT "ELITE A" PRINT "Assembled at ", ~S1% PRINT "Ends at ", ~P% PRINT "Code size is ", ~(P% - S1%) PRINT "Execute at ", ~LOAD% PRINT "Reload at ", ~LOAD_A% PRINT "S.ELTA ", ~S1%, " ", ~P%, " ", ~LOAD%, " ", ~LOAD_A% SAVE "output/ELTA.bin", S1%, P%, LOAD%