[Coco] Hello World part3

[Roger Taylor]

Here's a very short Hello World example.

         org     12000
msg     fcc     "HELLO WORLD OF ASSEMBLY"
         fcb     13,0
start   ldx     #msg    point to our message
p@      lda     ,x+     get current ASCII character
         beq     x@      exit if it's the NULL-terminator
         jsr     [40962] print the character using stdout hook
         bra     p@      keep printing
x@      rts
         end     start





At 03:27 PM 1/21/2004 -0500, you wrote:
>It has been mentioned that assembly programming is not done in a vacuum. 
>There is normally an operating system (OS) present and it make sense to 
>use as many routines from the OS as possible in your own programs.
>
>Here is a version of Hello World that uses ROM routines. It will clear and 
>print to the screen regardless of Coco3 text mode; 32, 40, 80. This type 
>of coding requires a knowledge of the ROMs that can only be obtained from 
>sources such as the Unravelled series of books. They can be found on the 
>Internet with a good search engine.
>
>* HELLO WORLD USING ROM ROUTINES
>
>PRNSTR  EQU     $B99C   ROM PRINT STRING ROUTINE
>CLRSCR  EQU     $A910   ROM CLEAR SCREEN
>CURPOS  EQU     $88     CURRENT SCREEN POSITION, LOW RES
>CRSLOC  EQU     $FE00   "        "          FOR HIGH RES
>SMODE   EQU     $E7     SCREEN MODE 0=32COL,1=40COL,2=80COL
>
>         ORG     $7000
>START   JSR     CLRSCR
>         LDA     SMODE   FIND OUT WHICH TEXT SCREEN IS IN USE
>         BNE     HRES
>         LDX     #$4EA   CENTER OF LOW RES SCREEN
>         STX     CURPOS
>         BRA     NEXT
>HRES    LDX     CRSLOC
>         CMPA    #1
>         BEQ     MRES
>         LEAX    1670,X  ABOUT CENTER OF 80 COL. SCREEN
>         BRA     NEXT
>MRES    LEAX    824,X   ABOUT CENTER OF 40 COL. SCREEN
>NEXT    STX     CRSLOC
>         LEAX    MESGE-1,PCR     THE -1 IS NECESSARY
>         JSR     PRNSTR
>LOOP    BRA     LOOP
>
>MESGE   FCC     /Hello, World/
>         FCB     0
>
>         END     START
>
>
>--
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----------
Roger Taylor