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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...

I am trying to load and run my HILOADER in the C64 Macro Assembly Development System. It is supposed to load at 51200 and then use SYS 51200 to run. However it just crashes at this point. At load up, my C64 is just turned on with nothing else running. Has anyone else run this loader at this...

All, Is there a generally "Recognized Standard" for C64 Assembly Language? I have been using the full "C64 Macro Assembler Development System" and had assumed it was the fullest and most complete assembler package "officially" released by CBM (1982). Is this so? I also see the Merlin64...

All, I have acquired a number of older disks on eBay, some with Assemblers and others as "new" disks (boxes still in plastic). Many of these I want to keep as "my originals" while making copies of them, but the write-protect tabs keep lifting off and (potentially) locking up the 1541 drive...

This is a continuation of my previous thread on connecting Basic to Assembly. Thanks to all who responded. I got one small simple program (Basic -> Assembly -> Basic) to run nicely. I have used RTS, USR, SYS, $C000,$8000 etc. I thought I had "gotten it"!! However, all subsequent small...

This is probably obvious to all the experienced C64 programmers here, but to a new "retro" member (myself!) I was puzzled by how to connect Basic to Assembly with the USR function. Initially I loaded the Assembly Code at $8000 (Hex) and then composed a short Basic code to access it and see if...