AnachronautandClaude Opus 5
588e02aff5
The memory map gave CosmOS 0x0000 through 0x1FFF of Program Memory and applications 0x2000 and above. CosmOS is 8141 bytes at the previous commit, which is fifty one bytes short of the line, and the next thing added to it went over. GOING OVER DOES NOT FAIL WHERE IT HAPPENS. Nothing enforces the division: an application says where it goes with #Base and the loader puts it there, so a CosmOS that has grown past 0x1FFF simply has the next program loaded written over the end of it. What breaks is whichever part of the shell that program happened to cover, at whatever later moment somebody uses it. It turned up here as the monitor's assemble command answering "I do not know" to valid instructions, several commands into a session, on a machine that had booted perfectly well. Both halves are doubled: applications now start at 0x4000 in Program Memory and 0x2000 in Data Memory. That is 16K of code and 8K of data for the system, against the 8775 and 2948 it uses today. Both were on the same trajectory, and moving them together means the twenty files that say #Base are edited once rather than twice. The standalone loader's loadable.asm keeps its old base: it belongs to the loader CosmOS grew out of, not to CosmOS, and its addresses answer to a different program. The unbased-segment diagnostic keeps its old base too - it exists to produce an error message that names the address, and the message is what is recorded. Tests/docs.sh now reads the two limits out of the table in the README and measures both segments against them. It reads them rather than being told them because the table is the specification, and this is the second time in this project that the thing nobody checked is the thing that rotted. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW
75 lines
3.3 KiB
NASM
75 lines
3.3 KiB
NASM
; This is an implementation of The Sieve of Eratosthenes that finds all the primes between 2 and 255.
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#Include services.asm
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#Program
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#Base 0x4000
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start:
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; Search the list until we find a prime.
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SETD DataTop
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CCF ; Clear the carry flag. In later cycles, the carry flag will be set at the end of the next loop. We'll want it cleared.
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RSTA
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RSTB
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findPrimeLoop:
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LDB ; Load an element into B.
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BRB foundPrime ; If it's zero, it's a prime.
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INCA ; Increment A, our index.
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INCD ; Increment the Data Pointer.
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BRA end ; If A becomes zero, we've looked through the whole list without finding another prime.
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BRI findPrimeLoop ; Keep searching for the next prime.
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foundPrime:
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; If we've found a prime, we should print it and mark it off the list so we don't print it again.
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CALL printByteDecimal ; A contains our prime, so we can just call the print subroutine.
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CALL blankSpace ; Put a space afterward to keep things easy to read.
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INIB 0x01 ; Set B to 1.
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STB ; Mark this prime off the list.
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markMultiples:
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; Now, we mark each multiple of this prime as nonprime until we reach the end of the list.
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PSHD ; Save the Data Pointer to the stack.
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POPB ; Pop its low byte into B.
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ADD ; Add them together.
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PSHQ ; Store the result back onto the stack.
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POPD ; Pop the modified address into the Data Pointer.
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INIB 0x01 ; Set B to 1.
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STB ; Store B to mark the value as nonprime.
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BRC start ; If the previous add overflowed, the next nonprime is outside the range of our list, so start over with a new prime.
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BRI markMultiples ; Otherwise, loop again to mark the next multiple as nonprime.
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end:
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CALL lineFeed ; Print a linefeed to make it look nice.
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SWI osExit ; The program is done, we found all the primes!
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#Data
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#Base 0x2000
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; The table of our prime candidates. It has to begin on a page boundary: marking walks
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; the pointer's low byte and treats the carry out as running off the end of the table,
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; which only finds the right end if the table starts on one.
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#Align 0x100
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DataTop:
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0x01 0x01 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
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0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
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0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
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0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
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0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
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0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
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0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
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0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
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0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
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0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
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0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
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0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
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0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
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0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
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0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
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0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
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#Include print.asm
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