Recent content by AAGDOS

Thanks to Robbert and Bruce for the good information! I will follow up and get to the bottom of this.!!!! I have the books by Mark Andrews and Jim Butterfield, but had not yet really dug into the variables' values being expressed in floating point numbers! It was hard to "reverse engineer" from...

I am confused on how the BASIC Interpreter is formatting the values of integers? They do not seem to be either straight binary or BCD?? I typed in and ran a very simple BASIC program... 10 N=2 20 END Start of Basic (SOB) is correct at $0801. The code ends with 3 zeros at $0810. On Using the ML...

Thanks to Dave and others for the insight! This was more subtle than I had anticipated, and setting SEC at the start of the code works! I have done more of a "deep dive" into the books by 1) Bush and Holmes, and 2) Leventhal., and found far more explanation. Thanks also for pointing me toward...

Dave, I have no idea!! I didn't see anything about that in the C64 Reference Manual (CBM). I'll try that in the morning! Thanks. Anthony G

Dave, I changed the code to start with CLC as a second guess. It made no difference. After the BRK, the SR = B0, so the carry flag = 0. Does this answer anything?? Thanks. Anthony G

All, Please excuse what appears to be a stupid question! Is my SBC messed up or am I messed up??? I am subtracting 02-05 = -03 = FD. But my code gives FC???? LDA $$05 STA $0350 LDA #$02 SBC $0350 BRK SBC is supposed to be "Subtract Memory from Accumulator....", and I assume the...

I am getting weird results in loading and displaying the Floating Point Accumulator (FAC)? If I take 8000 (Hex) and load subroutine $B391 by, LDY #$00 LDA #$80 JSR $B391 BRK Then checking...gives... .M 0061 90 80 00 00 00 00 which is correct in $0061 -$0066...

All, I may be mis-understanding something in the BIT test...????? If I load $04-> Accumulator and $04-> $0360, and test.... CMP $0360 BEQ $0350 the Z flag is set to Z=1 and it branches correctly to $0350. If I replace CMP with BIT and test.... BIT $0360 BEQ $0350 it does not...

I have written a Quick Start Guide to Assembly Language Programing on the C64. Over the past year I had struggled to get the correct syntax and format for all the commands to run the Assembler, Loaders(2) and Monitors(2) in the Macro Assembler Development System (CBM 1982). I wrote this up for...

Has anyone copied a disk in the 1541-11 using program "SD.BACKUP.C64" from the "TEST/DEMO" 1541-11 diskette (CBM 198x) ? I tried last evening and it seemed stuck in a loop...I was switching disks every 2-3 seconds for over 15 minutes. Insert Source Disk, press SPACE Reading Buffer #1...

I am running many of my small Assembly Language codes on the VICE Emulator 3.1 on my PC Win 10. However, I have not (readily) found a guide or "help list" for some of the original C64 keys. Does anyone know of a good link to find them? For example.... CTRL RUN/STOP CLR/HOME When running under...

All, I have been writing many smaller Assembly Codes on my original Commodore 64 using the C64 Macro Assembler Development System (on disk in 1541). Full Editor, Assembler, Loader, Monitor ..etc for larger codes, Monitor$C000 for shorter codes. I have just downloaded WinVICE 3.1 x64 to run on...

I am writing a number of simple examples in Assembly Language for the C64 using CBM's ML Monitor$C000. However, the Monitor does not appear to accept Labels (e.g."Loop")? Is this true, or am I missing something? ML Monitor$C000 ------ .A 033C LDX #$04 .A 033E DEX .A 033F BNE...

I just posted this in the "marketplace", but am also posting it here under C64s ! I have a collection of four C64s retrieved from my closet after 30 years. I have disassembled and cleaned three of them to good working condition, but the 4th needs more repair skills than I have. Can anyone...

A number of articles have mentioned an "Easter Egg" that Microsoft put into the Basic that Commodore picked up and released (with some mods) as V2.0. The command "WAIT 6502" is supposed to show a pop up display "MICROSOFT!", even though it cannot be located with a dis-assembler. However, my C64...