Msg: 5248 *Conference*
07-31-94 16:24:00
From: COMET _
To : JOHN RUSSO
Subj: ROM ROUTINES
The BASIC "CALL" command allows you to pass control to a given address, and set the value of the "A" register and the "HL" register pair. Any ROM routines that require additional entry conditions (e.g. PLOT requires the "D" and "E" registers be given values) will not be able to be CALLed directly from BASIC; you will need to write a M/L program which loads values into these registers, and then jumps to the indicated address. There are a couple assembler programs which would allow you to write higher than machine language. These assemblers can be found in the progrm library. You'll need to know assembly language (and not just BASIC) in order to get much use of them, though. I'm a programmer by profession, and have ordered an assembly language book from Intel on the 8080/8085 CPU. Sometimes you will find books in your local public library, too. You can find good examples of assembly code by running a disassembler (also found in Club 100's library) on any LOADM'ed .CO files (which can get created from a .BA program, several examples in the Club 100 library).