greg76 · June 29, 2025 12:42
diff --git a/helloworld.asm b/helloworld.asm
 ;
 ; assembly example to write a message on the Commodore 64 screen
 ;

 ; address of the basic loader. the RUN command is looking for the first instruction here.
 ; the assembly code should be compiled to start here as well, so it can be run with a sys command
 *=$0801

 ; this is the basic loader, this is mimicing of jumping in to the assembly code with a sys command
 !byte $0c,$08,$b5,$07,$9e,$20,$32,$30,$36,$32,$00,$00,$00
 jmp main

 ; this is a "data segment" where we define our variables, strings, tables, any data your program needs
 .hellotext
    !scr "greetings to csillik rasterbar laszlo!",0
    !set ofs = 1            ; this is just an offset of how much the message should be shifted to the right.

 ; this is the actual code part that gets executed
 main 
    ldy #0                  ; y is one of the registers of the CPU we will use it to iterate over our message

 hello
    lda .hellotext,y        ; the y-th chacter of our message is loaded into the A register
    beq +                   ; branch on result zero (the message is zero padded, when A contains zero we should terminate
    sta $400+ofs,y          ; default display memory address (we store the character stored in reg. A on ofs+y -th position)
    lda #1                  ; color code of white (1) is loaded into reg. A (https://www.c64-wiki.com/wiki/Color)
    sta $d800+ofs,y         ; color ram (the color code has to be written to the color ram, offsetted with the same value)
    iny                     ; increment Y so we can read the next character and write it to the next location
    jmp hello
 +
    rts
	;
	; assembly example to write a message on the Commodore 64 screen
	;

	; address of the basic loader. the RUN command is looking for the first instruction here.
	; the assembly code should be compiled to start here as well, so it can be run with a sys command
	*=$0801

	; this is the basic loader, this is mimicing of jumping in to the assembly code with a sys command
	!byte $0c,$08,$b5,$07,$9e,$20,$32,$30,$36,$32,$00,$00,$00
	jmp main

	; this is a "data segment" where we define our variables, strings, tables, any data your program needs
	.hellotext
	!scr "greetings to csillik rasterbar laszlo!",0
	!set ofs = 1 ; this is just an offset of how much the message should be shifted to the right.

	; this is the actual code part that gets executed
	main
	ldy #0 ; y is one of the registers of the CPU we will use it to iterate over our message

	hello
	lda .hellotext,y ; the y-th chacter of our message is loaded into the A register
	beq + ; branch on result zero (the message is zero padded, when A contains zero we should terminate
	sta $400+ofs,y ; default display memory address (we store the character stored in reg. A on ofs+y -th position)
	lda #1 ; color code of white (1) is loaded into reg. A (https://www.c64-wiki.com/wiki/Color)
	sta $d800+ofs,y ; color ram (the color code has to be written to the color ram, offsetted with the same value)
	iny ; increment Y so we can read the next character and write it to the next location
	jmp hello
	+
	rts
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