                     MACHINE LANGUAGE - Part IV_
                         by Lyle Giese (LYLEG)


Welcome to this month's installment of how to talk to your computer in
its own language!  First of all, I know that at least one person reads
my column!

Bill Brier (a.k.a. TROUBLESOME) reports that the KERNAL routine
CHROUT($FFD2) does not corrupt the Accumlator even though CBM's
Programmers Reference Guide says so. He has used that routine on the 64
and C-128 without ever seeing the Accumlator change. (Probably on one or
more of the earlier PET's it did change the Accumlator's value and CBM
made the KERNAL chart from some of the old PRG'S. But that's just
speculation.)

This month's program will help us start doing I/O to the disk drive. My
example will create a SEQ file on your disk and send it (what else
but???) the alphabet. Here is the program:

         .A C000 LDA #$08
         .A C002 LDX #$08
         .A C004 LDY #$08
         .A C006 JSR $FFBA
         .A C009 LDA #$08
         .A C00B LDX #$45
         .A C00D LDY #$C0
         .A C00F JSR $FFBD
         .A C012 JSR $FFC0
         .A C015 BCC $C018
         .A C017 RTS
         .A C018 LDX #$08
         .A C01A JSR $FFC9
         .A C01D JSR $FFB7
         .A C020 BEQ $C023
         .A C022 RTS
         .A C023 LDA #$41
         .A C025 STA $FB
         .A C027 JSR $FFD2
         .A C02A JSR $FFB7
         .A C02D BNE $C037
         .A C02F INC $FB
         .A C031 LDA $FB
         .A C033 CMP #$5A
         .A C035 BCC $C027
         .A C037 LDA #$0D
         .A C039 JSR $FFD2
         .A C03C JSR $FFCC
         .A C03F LDA #$08
         .A C041 JSR $FFC3
         .A C044 RTS
         .M C045
         :C045 54 45 53 54 2C 53 2C 57 TEST,S,W


A little larger than our previous programs, but we are doing a lot with
it.

See you next month.

Lyle Giese (LYLEG)
