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

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

Cassette, Disc (flight), Disc (docked), 6502 Second Processor, Master and Electron

Code variations between these versions are shown below.

       Name: wW
       Type: Subroutine
   Category: Flight
    Summary: Start a hyperspace countdown


 Start the hyperspace countdown (for both inter-system hyperspace and the
 galactic hyperdrive).

Code variation 1 of 4A variation in the comments only

This variation is blank in the Cassette, Disc (flight), Disc (docked) and Electron versions.

6502SP, Master
 Other entry points:

   wW2                  Start the hyperspace countdown, starting the countdown
                        from the value in A


.wW

 LDA #15                \ The hyperspace countdown starts from 15, so set A to
                        \ 15 so we can set the two hyperspace counters

Code variation 2 of 4A variation in the labels only

This variation is blank in the Cassette, Disc (flight), Disc (docked) and Electron versions.

6502SP, Master
.wW2

 STA QQ22+1             \ Set the number in QQ22+1 to A, which is the number
                        \ that's shown on-screen during the hyperspace countdown

 STA QQ22               \ Set the number in QQ22 to 15, which is the internal
                        \ counter that counts down by 1 each iteration of the
                        \ main game loop, and each time it reaches zero, the
                        \ on-screen counter gets decremented, and QQ22 gets set
                        \ to 5, so setting QQ22 to 15 here makes the first tick
                        \ of the hyperspace counter longer than subsequent ticks

Code variation 3 of 4Minor and very low-impact

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

Cassette, Flight, Docked, 6502SP, Master
Electron
 TAX                    \ Print the 8-bit number in X (i.e. 15) at text location
 JMP ee3                \ (0, 1), padded to 5 digits, so it appears in the top
                        \ left corner of the screen, and return from the
                        \ subroutine using a tail call
IF _IB_SUPERIOR

 TAX                    \ Print the 8-bit number in X (i.e. 15) at text location
 JMP ee3                \ (0, 1), padded to 5 digits, so it appears in the top
                        \ left corner of the screen, and return from the
                        \ subroutine using a tail call

ELIF _IB_ACORNSOFT

 TAX                    \ Print the 8-bit number in X (i.e. 15) at text location
 JSR ee3                \ (0, 1), padded to 5 digits, so it appears in the top
                        \ left corner of the screen

 RTS                    \ Return from the subroutine

ENDIF

Code variation 4 of 4A variation in the comments only

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

Cassette
\.hy5                   \ This instruction and the hy5 label are commented out
\RTS                    \ in the original - they can actually be found at the
                        \ end of the jmp routine below, so perhaps this is where
                        \ they were originally, but the authors realised they
                        \ could save a byte by using a tail call instead of an
                        \ RTS?