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BillG

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About BillG

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    Space Invader

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  • Location
    North Tejas
  • Interests
    Programming and refurbishing vintage computers

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  1. The CP/M convention is that the letter 'Q' replaces the middle letter of the extension of files compressed with the SQ (squeeze) utility. Use USQ (unsqueeze) to decompress it.
  2. And yours has disk images; the other one does not.
  3. How much existing code uses just the register number instead of Rx? Is it worth a mode in which the assembler requires the Rx form?
  4. Amen to that. They only seem too many until you start using them. Earlier in the year, I started implementing clones of the old Space Voyage game for the SWTPC 6800 on other platforms. In the original 6800 version, has to be written on the 6502, due to the lack of a bls instruction.
  5. Segmentation on the x86 is something that the programmer had to get used to managing. I have done so much of it that it is second nature. The ironic thing is that IBM chose the 8088 for their small computer. The IBM mainframe architecture is notorious for how difficult it was to program. Addressing required using a base register. A section of code started with a BALR (BrAnch and Link Register) instruction to get something related to the current program counter into a register. All other branches must be offsets to that base address. IIRC, a section of code is limited to 4K bytes, so any sizeable program had to be broken up into small pieces.
  6. <snip> I do not own real hardware and use Steem and Devpac to do testing. I use my own cross assembler and emulator to do most of the development; everything so far treats the ST display and keyboard as a TTY.
  7. I find that programming the 6502 to manipulate 16-bit and larger quantities to be tedious. ADDQ instead of INX bothers me because as an addition operation, it affects the carry (and X) flag whereas an increment or decrement on most processors do not.
  8. It is probably historical. The first part is derived from CP/M --> Concurrent PC DOS --> DR DOS plus the GSX graphics extensions originally hosted by CP/M. The second part is the GEM GUI.
  9. Dec 13 was Friday the thirteenth. The previous Friday the thirteenth was 13 weeks prior; the next one is 13 weeks later...
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