The UNIX Time-Sharing System
1974 · paper · Computer science
Describes UNIX, a general-purpose multi-user interactive operating system for PDP-11/40 and 11/45 computers, covering its file system and command interface. The authors say it shows a powerful interactive system need not be expensive in equipment or effort.
Checked: PDF from cs.cmu.edu, fetched 4 Oct 2026. Page numbers are those of that PDF.
1 finding
Wording 'Wait may also present status from a grandchild or more distant ancestor; see §5.5.' should read 'more distant descendant'.
- p. 6 §5.4 Process Synchronization, last sentence
Wait may also present status from a grandchild or more distant ancestor; see §5.5.
- p. 6
Wait may also present status from a grandchild or more distant ancestor
Judge's note: Checked crop C004-a on p.6. wait returns status from the caller's children, and the same paragraph says 'An error return is taken if the calling process has no descendants.' A grandchild is a descendant, so 'or more distant ancestor' reverses the relationship. The fix is evident from context.
Second check: another model agreed
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5 minor (typos and the like; most checked by the judge only)
Wording §3.5 says set-user-ID changes the user ID 'to that of the creator of the file', but files are 'marked with the user ID of its owner' and §3.6.1 lists a call to 'change the protection mode or the owner of a file'.
- p. 3 §3.5 Protection, second paragraph
that of the creator of the file whenever the file is executed
- p. 4 §3.6.1 Other I/O Calls
change the protec- tion mode or the owner of a file
- p. 3 §3.5 Protection, first two paragraphs
to that of the creator of the file whenever the file is executed
- p. 3 §3.5 Protection
it is marked with the user ID of its owner
Judge's note: Checked crops C002-a and C002-b. On p.3, §3.5 says a new file is marked with its owner's user ID; the next paragraph says set-user-ID switches to the 'creator'. On p.4, §3.6.1 provides a call to change a file's owner. Because the owner can change, 'creator' and 'owner' can differ, and the later mkdir example ('owned by the super-user') points to the owner. This is loose wording rather than a substantive error.
Second check: another model agreed
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Wording In §9.3 '1.6% backup dumper' is followed by '1.8% assembler', and the right column starts at '1.7% Fortran compiler', breaking the otherwise descending order.
- p. 11 §9.3 Command CPU Usage, end of left column
1.6% backup dumper
- p. 11 §9.3 Command CPU Usage, last left-column entry
1.8% assembler
Only the authors can say what is right here.
Judge's note: Checked crop C007-a on p.11. The left column reads 15.7, 15.2, 11.7, 5.8, 5.3, 3.3, 3.1, 1.6, 1.8; the right column reads 1.7, 1.6, 1.6, 1.6, 1.4, 1.3, 1.3, 1.1, 1.0. The §9.4 list in the same crop is also in descending order. Either the assembler row is out of place or one of the two percentages is misprinted; only the authors can say which.
Second check: another model agreed
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Wording 'Files on that disk were backed up three days.' appears to be missing a word (e.g. 'every three days' or 'three days earlier').
- p. 11 §9.5 Reliability, second paragraph
Files on that disk were backed up three days.
Only the authors can say what is right here.
Judge's note: Checked crop C009-a on p.11. The sentence reads exactly as quoted. It can mean either a three-day backup cycle or a backup made three days before the loss, so the intended meaning is unclear.
Second check: another model agreed
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Typo 'the large disk drive, which contains user's files' should be 'users' files' (plural possessive).
- p. 3 §3.4 Removable File Systems
which contains user's files
Judge's note: Checked crop C003-a: p.3, §3.4 prints 'user's files'. The large drive holds files for all users, and with no article the singular possessive reads as an apostrophe slip.
Second check: none (judge only)
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Typo 'We be-' / 'believe that a properly-designed interactive system' prints a duplicated syllable; should be 'We believe'.
- p. 10
We be- believe that a properly-designed interactive system
Judge's note: Checked crop C006-a on p.10, left column. The printed page itself has 'We be-' at a line end followed by 'believe' on the next line, so the duplication is in the typesetting, not an extraction artefact.
Second check: none (judge only)