C64 Programmer's Reference Guide: BASIC to Machine Language

If we write a program with 64MON and put the BRK instruction at the end, then when the program is executed, it will return to 64MON when it is finished. This might not happen if there is a mistake in your program, or the BRK instruction is never reached (just like an END statement in BASIC may never get executed). This means that if the Commodore 64 didn't have a STOP key, you wouldn't be able to abort your BASIC programs!

WRITING YOUR FIRST PROGRAM

If you've used the POKE statement in BASIC to put characters onto the screen, you're aware that the character codes for POKEing are different from CBM ASCII character values. For example, if you enter:

   PRINT ASC("A") (and press <RETURN> )

the Commodore 64 will respond with:

   65

   READY.

However, to put an "A" onto the screen by POKEing, the code is 1, enter:

   <SHIFT+CLR/HOME> to clear the screen

   POKE 1024,1:POKE 55296,14 (and <RETURN> (1024 is the start of screen
   memory)

The "P" in the POKE statement should now be an "A." Now let's try this in machine language. Type the following in 64MON: (Your cursor should be flashing alongside a "." right now.)

   .A 1400 LDA#$01 (and press <RETURN>)

This page has been created by Sami Rautiainen.
Read the small print.	Last updated July 10, 2002.