The answer says

You probably predicted a height of 8.9861

I wonder which calculations should be made to predict such a height. The most simple calculations produce the value 8.98608, namely:

Take the old height (6.83331) and add to it the amount of shift (2.15277), which yields 6.83331+2.15277=8.98608

  • My TeXbook doesn't even have that comment (commenting on the width instead). Moreover, the "old height" is 6.83333. Commented Oct 1, 2020 at 8:39
  • @DonaldArseneau My copy has the comments as Igor's
    – Joseph Wright
    Commented Oct 1, 2020 at 8:53
  • I agree the comment doesn't really make sense: there's no reason to work in pt here as we know the sizes the information earlier in the chapter
    – Joseph Wright
    Commented Oct 1, 2020 at 8:54
  • Possibly a mix-up due to the shift from AM to CM fonts.
    – egreg
    Commented Oct 1, 2020 at 9:20
  • I would guess that there was some mix-up with old and new numbers at the time the fonts were changed (@egreg), and Don noticed (1) the discrepancy in width was gone, and (2) the new height didn't match the height calculated from the old original log listing. Commented Oct 1, 2020 at 9:32

1 Answer 1


Congratulations. I think you've found an error in The TeXbook. However, apparently according to https://www-cs-faculty.stanford.edu/~knuth/abcde.html there are printings that include changes not included in the errata files on ctan and it's unclear that the texbook.tex source on ctan (which includes this error) is the same as the latest printing.

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