AnachronautandClaude Opus 5
023362b05a
A screen drawn where it can be seen is seen half drawn. A program that moves forty things and rewrites the map underneath them is wrong for as long as it takes to put them all right, and at a megahertz that is long enough to look at. So the device brings a second screen bank, on port 0x3B, and port 0x3C says which of the two is displayed. Everything a program draws into the other one is invisible until one byte shows the whole of it at once. ONE REGISTER IS ENOUGH, where the hardware this imitates needed two. The other said which screen the CPU's window pointed at; there is no window here, because a program reaches a bank through the memory controller by its number. Writing to the screen that is not shown is a matter of naming its bank, and the device never has to be told. And a flip cannot tear: a frame is drawn from one bank in one go, so a flip either happened before that frame or happens before the next. There is nothing to race, where the real machines had to catch the few lines between frames to swap in. The console draws into whichever screen is displayed rather than one of its own, so a fault message lands where somebody can read it even if a game had flipped. And CosmOS puts the displayed screen back at exit, the way it already puts back the cursor and the ink: a program that faulted while flipped could not have, and a shell that only came out right for programs which remembered would come out wrong the day one crashed. Flip.asm is the worked example. It deliberately does NOT restore the display itself - that is the point of the paragraph above, and it is what makes the system's guarantee the thing under test rather than the program's good manners. Written the other way round first, where it passed with the guarantee deleted. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW
129 lines
3.2 KiB
Plaintext
129 lines
3.2 KiB
Plaintext
CosmOS
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> monitor
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x examine, d disassemble, a assemble, s set, b bank, g go, exit leaves
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* b nonsense
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b <program|data|number>
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* b 9
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there is no such bank
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* load greet.sbx
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loaded, starting at 5000
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* b program
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bank 00
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* d 5000
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5000 47 00 30 00 SETD.0 3000
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5004 72 10 SWI 10
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5006 47 00 30 44 SETD.0 3044
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500A 72 10 SWI 10
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500C 47 00 30 7A SETD.0 307A
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5010 27 1F INIB 1F
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5012 72 11 SWI 11
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5014 47 00 30 5D SETD.0 305D
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* x 5000
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5000 47 00 30 00 72 10 47 00 30 44 72 10 47 00 30 7A G.0.r.G.0Dr.G.0z
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5010 27 1F 72 11 47 00 30 5D 72 10 47 00 30 7A 72 10 '.r.G.0]r.G.0zr.
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5020 47 00 30 65 72 10 20 72 12 00 00 00 00 00 00 00 G.0er. r........
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5030 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
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* b data
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bank 01
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* x 3000
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3000 61 20 70 72 6F 67 72 61 6D 2C 20 6C 6F 61 64 65 a program, loade
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3010 64 20 6F 66 66 20 61 20 64 69 73 6B 2C 20 72 75 d off a disk, ru
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3020 6E 6E 69 6E 67 20 6F 6E 20 74 68 65 20 73 79 73 nning on the sys
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3030 74 65 6D 20 74 68 61 74 20 6C 6F 61 64 65 64 20 tem that loaded
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* b 2
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bank 02
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* x 0
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0000 01 FF 00 00 00 00 00 00 01 FF 00 00 00 00 00 00 ................
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0010 03 FF 08 00 00 00 00 00 01 20 01 00 00 00 00 00 ......... ......
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0020 00 FF 00 00 00 00 00 00 00 FF 00 00 00 00 00 00 ................
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0030 00 FF 00 00 00 00 00 00 00 FF 00 00 00 00 00 00 ................
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* s 0 FF
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that bank will not be written
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* b program
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bank 00
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* s 8000 26 48 D1 00 26 0A D1 00 18 12
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* d 8000
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8000 26 48 INIA 48
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8002 D1 00 OUTA 00
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8004 26 0A INIA 0A
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8006 D1 00 OUTA 00
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8008 18 SHR
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8009 12 AND
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800A 00 ?
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800B 00 ?
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* g 8000
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H
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that byte is not an instruction, at 800A
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A 85 B 3F Q 05
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the program was stopped
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* d 8000
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8000 26 48 INIA 48
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8002 D1 00 OUTA 00
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8004 26 0A INIA 0A
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8006 D1 00 OUTA 00
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8008 18 SHR
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8009 12 AND
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800A 00 ?
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800B 00 ?
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* b data
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bank 01
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* s 8100 68 65 6C 6C 6F 2C 20 74 79 70 65 64 0A 00
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* b program
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bank 00
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* a 8200
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8200: SETD.0 8100
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8204: SWI 10
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8206: lda.2
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8208: LDD.0.1
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820B: frobnicate
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no such instruction
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820B: INIA
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that one needs a value after it
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820B: SWI 12
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820D: .
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* d 8200
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8200 47 00 81 00 SETD.0 8100
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8204 72 10 SWI 10
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8206 42 02 LDA.2
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8208 4A 00 01 LDD.0.1
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820B 72 12 SWI 12
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820D 00 ?
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820E 00 ?
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820F 00 ?
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* g 8200
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hello, typed
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finished
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* exit
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> dir
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greet.sbx 211
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hello.sbx 53
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Life.sbx 1396
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Snake.sbx 2164
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Keys.sbx 664
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Say.sbx 156
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Break.sbx 149
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Grid.sbx 571
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Press.sbx 872
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Mode.sbx 48
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Flip.sbx 291
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Crash.sbx 632
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vars.script 50
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blocks.script 343
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loops.script 272
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tune.sbx 306
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notes.txt 21
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Apps <dir>
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hi.script 121
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bad.script 45
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plain.script 24
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cross.script 280
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nonl.script 38
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outer.script 376
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inner.script 44
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loop.script 35
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25 files, 1 directory
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> exit
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halted
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Execution halted.
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[exit 0]
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