Version analysis of DELT - Elite on the BBC Micro and NES

This code appears in the following versions (click to see it in the source code):

Disc (docked), 6502 Second Processor and Master

Code variations between these versions are shown below.

       Name: DELT
       Type: Subroutine
   Category: Save and load
    Summary: Catalogue a disc, ask for a filename to delete, and delete the
             file


 This routine asks for a disc drive number, and if it is a valid number (0-3)
 it displays a catalogue of the disc in that drive. It then asks for a filename
 to delete, updates the OS command at DELI so that when that command is run, it
 deletes the correct file, and then it does the deletion.


 Other entry points:

   DELT-1               Contains an RTS


.DELT

 JSR CATS               \ Call CATS to ask for a drive number (or a directory
                        \ name on the Master Compact) and catalogue that disc
                        \ or directory

 BCS SVE                \ If the C flag is set then an invalid drive number was
                        \ entered as part of the catalogue process, so jump to
                        \ SVE to display the disc access menu

Code variation 1 of 6Specific to an individual platform

Tap on a block to expand it, and tap it again to revert.

Docked
Master
6502SP
 LDA CTLI+1             \ The call to CATS above put the drive number into
 STA DELI+4             \ CTLI+1, so copy the drive number into DELI+4 so that
                        \ the drive number in the "DE.:0.E.1234567" string
                        \ gets updated (i.e. the number after the colon)
IF _SNG47

 LDA CTLI+4             \ The call to CATS above put the drive number into
 STA DELI+8             \ CTLI+4, so copy the drive number into DELI+8 so that
                        \ the drive number in the "DELETE :1.1234567" string
                        \ gets updated (i.e. the number after the colon)

ENDIF
 LDA CTLI+1             \ The call to CATS above put the drive number into
 STA DELI+7             \ CTLI+1, so copy the drive number into DELI+7 so that
                        \ the drive number in the "DELETE:0.E.1234567" string
                        \ gets updated (i.e. the number after the colon)

Code variation 2 of 6Related to the Master version

When deleting a file via the disc menu, the disc and 6502SP versions ask for the "FILE TO DELETE?", while the Master version asks for the "COMMANDER'S NAME?".

Tap on a block to expand it, and tap it again to revert.

Docked, 6502SP
Master
 LDA #9                 \ Print extended token 9 ("{clear bottom of screen}FILE
 JSR DETOK              \ TO DELETE?")
 LDA #8                 \ Print extended token 8 ("{single cap}COMMANDER'S
 JSR DETOK              \ NAME? ")

 JSR MT26               \ Call MT26 to fetch a line of text from the keyboard
                        \ to INWK+5, with the text length in Y

 TYA                    \ If no text was entered (Y = 0) then jump to SVE to
 BEQ SVE                \ display the disc access menu

Code variation 3 of 6A variation in the comments only

Tap on a block to expand it, and tap it again to revert.

Docked
Master
6502SP
                        \ We now copy the entered filename from INWK to DELI, so
                        \ that it overwrites the filename part of the string,
                        \ i.e. the "E.1234567" part of "DE.:0.E.1234567"

 LDX #9                 \ Set up a counter in X to count from 9 to 1, so that we
                        \ copy the string starting at INWK+4+1 (i.e. INWK+5) to
                        \ DELI+5+1 (i.e. DELI+6 onwards, or "E.1234567")
IF _SNG47

                        \ We now copy the entered filename from INWK to DELI, so
                        \ that it overwrites the filename part of the string,
                        \ i.e. the "E.1234567" part of "DELETE :1.1234567"

 LDX #9                 \ Set up a counter in X to count from 9 to 1, so that we
                        \ copy the string starting at INWK+4+1 (i.e. INWK+5) to
                        \ DELI+9+1 (i.e. DELI+10 onwards, or "1.1234567")
                        \
                        \ Note that this is a bug - X should be set to 8, as a
                        \ value of 9 overwrites the first character of the
                        \ "SAVE" command in savosc
                        \
                        \ This means that if you delete a file, it breaks the
                        \ save command, so you can't save a commander file if
                        \ you have previously deleted a file

ELIF _COMPACT

                        \ We now copy the entered filename from INWK to DELI, so
                        \ that it overwrites the filename part of the string,
                        \ i.e. the "1234567890" part of "DELETE 1234567890"

 LDX #8                 \ Set up a counter in X to count from 8 to 0, so that we
                        \ copy the string starting at INWK+5+0 (i.e. INWK+5) to
                        \ DELI+7+0 (i.e. DELI+7 onwards, or "1234567890")

ENDIF
                        \ We now copy the entered filename from INWK to DELI, so
                        \ that it overwrites the filename part of the string,
                        \ i.e. the "E.1234567" part of "DELETE:0.E.1234567"

 LDX #9                 \ Set up a counter in X to count from 9 to 1, so that we
                        \ copy the string starting at INWK+4+1 (i.e. INWK+5) to
                        \ DELI+8+1 (i.e. DELI+9 onwards, or "E.1234567")

.DELL1

Code variation 4 of 6Specific to an individual platform

Tap on a block to expand it, and tap it again to revert.

Docked
Master
6502SP
 LDA INWK+4,X           \ Copy the X-th byte of INWK+4 to the X-th byte of
 STA DELI+5,X           \ DELI+5

 DEX                    \ Decrement the loop counter

 BNE DELL1              \ Loop back to DELL1 to copy the next character until we
                        \ have copied the whole filename
IF _SNG47

 LDA INWK+4,X           \ Copy the X-th byte of INWK+4 to the X-th byte of
 STA DELI+9,X           \ DELI+9

 DEX                    \ Decrement the loop counter

 BNE DELL1              \ Loop back to DELL1 to copy the next character until we
                        \ have copied the whole filename

 JSR getzp              \ Call getzp to store the top part of zero page in the
                        \ the buffer at &3000, as it gets corrupted by the MOS
                        \ during disc access

ELIF _COMPACT

 LDA INWK+5,X           \ Copy the X-th byte of INWK+5 to the X-th byte of
 STA DELI+7,X           \ DELI+7

 DEX                    \ Decrement the loop counter

 BPL DELL1              \ Loop back to DELL1 to copy the next character until we
                        \ have copied the whole filename

 JSR NMIRELEASE         \ Release the NMI workspace (&00A0 to &00A7) so the MOS
                        \ can use it, and store the top part of zero page in the
                        \ the buffer at &3000, as it gets corrupted by the MOS
                        \ during disc access

ENDIF
 LDA INWK+4,X           \ Copy the X-th byte of INWK+4 to the X-th byte of
 STA DELI+8,X           \ DELI+8

 DEX                    \ Decrement the loop counter

 BNE DELL1              \ Loop back to DELL1 to copy the next character until we
                        \ have copied the whole filename

 LDX #LO(DELI)          \ Set (Y X) to point to the OS command at DELI, which
 LDY #HI(DELI)          \ contains the DFS command for deleting this file

Code variation 5 of 6Specific to an individual platform

Tap on a block to expand it, and tap it again to revert.

Docked, Master
6502SP
 JSR OSCLI              \ Call OSCLI to execute the OS command at (Y X), which
                        \ catalogues the disc
 JSR SCLI2              \ Call SCLI2 to execute the OS command at (Y X), which
                        \ deletes the file, setting the SVN flag while it's
                        \ running to indicate disc access is in progress

Code variation 6 of 6Specific to an individual platform

This variation is blank in the Disc (docked) and 6502 Second Processor versions.

Master
 JSR getzp              \ Call getzp to restore the top part of zero page from
                        \ the buffer at &3000

 JMP SVE                \ Jump to SVE to display the disc access menu and return
                        \ from the subroutine using a tail call