Copyright
N60 BASIC
A copyright signature for NOSTROMO occupied the first 9 lines of the BASIC portion.
A player would have to LIST out the BASIC program after loading to have a chance to ever encounter this copyright message.
It does not show up anywhere, ever, in the running game itself.
1 REM************************** 2 REM* * 3 REM* NOSTROMO * 4 REM* * 5 REM* Copyright 1982 ASCII * 6 REM* * 7 REM* by HIROMI OHBA * 8 REM* * 9 REM**************************
6809
One decision when porting I had to make came down to “what should I do with these 9 lines?”
Just delete them?
That didn't seem right.
Instead, I thought the copyright REMarks could make a screen of their own to expose the credits rather than skip, ignore, or delete them.
There were a number of choices of how I could turn these lines into a screen:
- Create a 32×16 block of data and copy it to screen RAM
- Clear the screen somewhere, and copy the 9 lines one after another, spaces and all into a block on the cleared screen
- Clear screen, draw each star as a box and put each specific centered string in their specific place
The first option drastically wastes memory in the assembled binary: 512 bytes plus code to copy it to the screen.
The second option uses far less memory, holding only 26×9 bytes to place on the screen, and the code to do so, something having 9 print statements in a row.
But all those spaces …
The third option requires the most lines of source code to implement, but ends up using the least space in the assembled binary or memory.
To do this I created and leveraged these functions:
- CLEAR SCREEN - a general function I'd already created elsewhere
- COLOR1 - a simple convenience to reuse code for common color setting events
- HLINE - draw a horizontal line of repeating characters, such as asterisks
- VLINE - draw a vertical line of repeating characters
- PRINTAT - place a string at a given location on screen
- INITTMR - initialize a countdown timer
- WAITSYNC - wait for the vertical sync pulse, 50 or 60 of them equals 1 second
With that, drawing the the copyright onto the screen broke down into seven steps
- Use HLINE to place the top of the box characters on screen
- Use VLINE to place the left side of the box characters on screen
- Use VLINE to create the right side of the box characters on screen
- Use HLINE to place the bottom line of the box characters on screen
- Use PRINTAT to write NOSTROMO as a single string
- Use PRINTAT to write Copyright 1982 ASCII as a single string
- Use PRINTAT to write by HIROMI OHBA as a single string
Finally, I needed a pause of some sort before moving on to give the player a short opportunity to see the screen before moving on, without leaving it on screen so long it becomes an irritation over many starts.
Since the game already required a seconds countdown timer, I could use that.
So this is what I came up with expose the copyright remarks as a new screen, rather than skip over or simply delete them unused.
;*********************************************************************
;* COPYRIGHT
;* Display a copyright screen from original REM statements
;* Entry Values
;* None
;* Exit Values
;* None
;* Control Register Modifications
;* A,X,Y
;* Subroutines Called
;* COLOR1,HLINE,VLINE,PRINTAT
;*********************************************************************
COPYRIGHT: ; 1 REM**************************
; 2 REM* *
; 3 REM* NOSTROMO *
; 4 REM* *
; 5 REM* Copyright 1982 ASCII *
; 6 REM* *
; 7 REM* by HIROMI OHBA *
; 8 REM* *
; 9 REM**************************
; 12345678901234567890123456
lbsr COLOR1 ; Setup white letters on black background
BAS0001: ; Draw box top
lda #3 ; start drawing at ...
sta TX ; ... column 3
sta TY ; ... row 3
lda #29 ; for 29 horizontal characters
sta INDEXIX ; working varable for horizontal count
ldb #$6A ; '* to draw
lbsr HLINE ; now go draw horizonal line of *
; Draw box left side
ldd #$0304 ; draw vertical line of * at column 3
sta TX ; ... column 3
stb TY ; ... row 4
lda #11 ; for 8 vertical characters
sta INDEXIY ; working variable for vertical count
ldb #$6A ; '* to draw
lbsr VLINE ; now go draw vertical line of *
; Draw box right side
ldd #$1C04 ; draw vertical line of * at column 29
sta TX ; ... column 29
stb TY ; ... row 4
lda #11 ; for 8 vertical characters
sta INDEXIY ; working varable for vertical count
ldb #$6A ; '* to draw
lbsr VLINE ; now go draw vertical line of *
; Draw box bottom
ldd #$030B ; start drawing at ...
sta TX ; ... column 3
stb TY ; ... row 11
lda #29 ; for 29 horizontal characters
sta INDEXIX ; working variable for horizontal count
ldb #$6A ; '* to draw
lbsr HLINE ; now go draw horizontal line of *
; Draw TXTNAME program name message
ldd #$0C05 ; start drawing at ...
sta TX ; ... column 12
stb TY ; ... row 5
ldx #TXTNAME ; load X with pointer to string
stx STRPTR ; ... and store in temp
lda #8 ; load Y with length of string
sta STRLEN ; ... and store in temp
lbsr PRINTAT ; now go print string at
; Draw TXTCOPY copyright message
ldd #$0707 ; start drawing at ...
sta TX ; ... column 7
stb TY ; ... row 7
ldx #TXTCOPY ; load X with pointer to string
stx STRPTR ; ... and store in temp
lda #20 ; load Y with length of string
sta STRLEN ; ... and store in temp
lbsr PRINTAT ; now go print string at
; Draw TXTAUTH author message
ldd #$0909 ; start drawing at ...
sta TX ; ... column 12
stb TY ; ... row 9
ldx #TXTAUTH ; load X with pointer to string
stx STRPTR ; ... and store in temp
lda #14 ; load Y with length of string
sta STRLEN ; ... and store in temp
lbsr PRINTAT ; now go print string at
; FIXME TEST CODE
lbsr INITTMR ; INITIALIZE TIMER ROUTINE
lda #1 ; LETS WAIT 5 SECONDS
sta SECONDS ; STORE FOR NUMBER OF SECONDS TO WAIT
WAIT1: lbsr WAITSYNC ; WAIT FOR VSYNC
lda SECONDS ; HAS SECONDS COUNTED OUT TO 0?
cmpa #0 ; Out of Seconds?
bne WAIT1 ; NO, SECONDS WAS > 0 SO WAIT MORE
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