Elite on the BBC Micro and NES

# Universe: Ze

## [Acorn Electron version]

```       Name: Ze                                                      [Show more]
Type: Subroutine
Category: Universe
Summary: Initialise the INWK workspace to a hostile ship
Deep dive: Fixing ship positions
Context: See this subroutine in context in the source code
Variations: See code variations for this subroutine in the different versions
References: This subroutine is called as follows:
* DEATH calls Ze
* Main game loop (Part 3 of 6) calls Ze
* Main game loop (Part 4 of 6) calls Ze

Specifically, this routine does the following:

* Reset the INWK ship workspace

* Set the ship to a fair distance away in all axes, in front of us but
randomly up or down, left or right

* Give the ship a 4% chance of having E.C.M.

* Set the ship to hostile, with AI enabled

This routine also sets A, X, T1 and the C flag to random values.

Note that because this routine uses the value of X returned by DORND, and X
contains the value of A returned by the previous call to DORND, this routine
does not necessarily set the new ship to a totally random location. See the
deep dive on "Fixing ship positions" for details.

.Ze

JSR ZINF               \ Call ZINF to reset the INWK ship workspace

JSR DORND              \ Set A and X to random numbers

STA T1                 \ Store A in T1

AND #%10000000         \ Extract the sign of A and store in x_sign
STA INWK+2

TXA                    \ Extract the sign of X and store in y_sign
AND #%10000000
STA INWK+5

LDA #32                \ Set x_hi = y_hi = z_hi = 32, a fair distance away
STA INWK+1
STA INWK+4
STA INWK+7

TXA                    \ Set the C flag if X >= 245 (4% chance)
CMP #245

ROL A                  \ Set bit 0 of A to the C flag (i.e. there's a 4%
\ chance of this ship having E.C.M.)

ORA #%11000000         \ Set bits 6 and 7 of A, so the ship is hostile (bit 6
\ and has AI (bit 7)

STA INWK+32            \ Store A in the AI flag of this ship

\ Fall through into DORND2 to set A, X and the C flag
\ randomly
```