Version analysis of ee3 - Elite on the 6502

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: ee3
       Type: Subroutine
   Category: Flight
    Summary: Print the hyperspace countdown in the top-left of the screen

Code variation 1 of 4A variation in the comments only

This variation is blank in the Master version.

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

Cassette, Electron
Flight, Docked, 6502SP
 Print the 8-bit number in X at text location (0, 1). Print the number to
 Print the 8-bit number in X at text location (1, 1). Print the number to

 5 digits, left-padding with spaces for numbers with fewer than 3 digits (so
 numbers < 10000 are right-aligned), with no decimal point.


 Arguments:

   X                    The number to print


.ee3

Code variation 2 of 4Related to the screen mode

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

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Master
6502SP
 LDA #RED               \ Switch to colour 2, which is red in the space view
 STA COL
 LDA #RED               \ Send a #SETCOL RED command to the I/O processor to
 JSR DOCOL              \ switch to colour 2, which is red in the space view

Code variation 3 of 4Related to a standard feature

The cassette and Electron versions print the right-aligned hyperspace countdown in column 0, while the other versions print it one column to the right in column 1.

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Cassette, Electron
Flight, Docked
Master
6502SP
 LDY #1                 \ Move the text cursor to row 1
 STY YC

 DEY                    \ Decrement Y to 0 for the high byte in pr6

 STY XC                 \ Move the text cursor to column 0
 LDY #1                 \ Move the text cursor to column 1
 STY XC

 STY YC                 \ Move the text cursor to row 1

 DEY                    \ Decrement Y to 0 for the high byte in pr6
 LDA #1                 \ Move the text cursor to column 1
 STA XC

 STA YC                 \ Move the text cursor to row 1

 LDY #0                 \ Set Y = 0 for the high byte in pr6
 LDA #1                 \ Move the text cursor to column 1 on row 1
 JSR DOXC
 JSR DOYC

 LDY #0                 \ Set Y = 0 for the high byte in pr6

Code variation 4 of 4Related to the Master version

The Master version's hyperspace countdown is padded to 3 characters rather than 5, so it appears two characters to the left compared to the disc and 6502SP versions.

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Cassette, Flight, Docked, 6502SP, Electron
Master
                        \ Fall through into pr6 to print X to 5 digits, as the
                        \ high byte in Y is 0
 CLC                    \ Call TT11 to print X to 3 digits with no decimal point
 LDA #3                 \ and return from the subroutine using a tail call
 JMP TT11