Errata
The following is a list of some of the errors in the text
"Computer Theory" by Cohen, 2nd ed. Most of these were
uncovered by David F. Appleyard (DFA). Please report any
more to me for inclusion on this list.

Part I
Ch. 1
  p. 4, line 19, replace "weather" by "whether".
Ch. 2
Ch. 3
Ch. 4
  p. 41, line -13 (13th from the bottum) delete "whether" or "if".
         line -2, delete ".". 
Ch. 5
  p. 55, line -3, replace "..." by "...qn".
         line -1, replace "..." by "...xm".
  p. 56, replace "xk" by "qk".
  p. 71, line 10, replace "2-3" by "2-2-3".
Ch. 6
  p. 86, line 7, replace "not only" by "only".
Ch. 7
  p. 95, line 7, The empty set is not a regular expression, according to
                 the def. of regular expression.
  p. 98, line 5, replace "unless" by "useless"
  p. 100, line 13, replace "being" by "begin"
  p. 107, 2nd graph, place an "a" on the bottum loop.
  p. 110, line 30, replace "send" by "sends".
  p. 116, line 4, replace "form" by "from".
  p. 120, line 17, add "(we have just looped from y1 back to y1,
                   while running on FA2)".
  p. 124, line 7, replace "loose" by "lose".
  p. 131, line 11, replace "z2" by "z4".
  p. 132, line 25, replace "FA2" by "FA*".
  p. 139, 2nd graph, add a "b" to the edge from x4 to empty.
          4th graph, replace "x2 or x3" by "x1 or x2 or x3".
  p. 140, 2nd graph, 
            replace in the upper right state "1 or 2 or 3" by "1 or 2 or 3 or 4",
	    replace in the lower middle state "1 or 3 or 6" by "1 or 5 or 6", and
	    replace in the lower right state "1 or 4" by "1 or 4 or 5 or 6".	  		      
Ch. 8
Ch. 9
  p. 177, line 11, replace "for l1" by "for L2".
  p. 179, line -3(3rd from the bottum) replace "L1" and "r1" by "L2" and "r2".
Ch. 10
  p. 200, lines -3 and -7, replace "R/Q" by "R/P".
Ch. 11

Part II
Ch. 12
  p. 235, line 24, replace "fix" by "first".
  p. 237, line 8, interchange "left" and "right".
  p. 239, line -11, replace "At" by "All".
  p. 255, line 2, "aX" not "ax".
Ch. 13
  p. 273, line -1, B -> S|a|b.
Ch. 14
  p. 307, line -3, replace "within" by "with".
Ch. 15
  p. 319, In the chart the label on the edge from POP to PUSH C 
          should be "A" not "S".
  p. 328  line 4 should read
     "All branching, in or out, deterministic or nondeterministic, ...".
  p. 330  The discussion of Condition 5 should also include the rectification
    of the case when multiple branches are entering a POP. This can be handled
    either by bifurcating the POP into multiple POP's with one incoming branch
    each or by replacing it by a HERE (which allows branching in and out 
    followed by a POP. 
  p. 331, Top chart: Delete the arrowhead coming into PUSH a from the left.
  p. 331, Bottom chart: The POP state leading into the accept state should
    be labelled POP3. And, to be consistent with the next page as well as
    the preceding discussion, this PDA should have no b-edge from READ2 to POP1.
    Instead, it should have a b-edge to the new state POP7 just to its left, 
    and then POP7 should have an a-edge straight up to the HERE state.
  p. 335, Step 4: insert joint-consistent and" in front of "STACK-consistent".	  
  p. 345, Note that the POP in the PDA shown gets replaced by a HERE on the
    next page folllowed by POP's.
Ch. 16
  p. 354, line -14. "node" not "mode".
  p. 365, line 3: "on" not "of".
  p. 372, third paragraph, second sentence is false; v could be all b's and y
    all a's, for example. But by pumping once we can get the contradiction.
Ch. 17
  p. 383, line -2, make that "(baabbbbb)(a)"
  p. 392, line -8, append "in" to the line.
Ch. 18
  p. 410, line 10, replace "B->A" by "B->bAA".

Part III
Ch. 19
Ch. 20
Ch. 21\
Ch. 22
Ch. 23
  p. 544, line 17, replace "closure" by "intersection"
  p. 563, 3rd diagram, the two rightmost edges should point to the right.
Ch. 24
  p. 579, line -1, replace q1 by q0.
  p. 580 , first line of 2nd paragraph. Insert "only" to obtain 
     "grammar only for".
  p. 582, fist line after the black square, replace "1 through 7" by 
     "1 through 6".
  p. 584, line -1. Replace p.575 by p. 576.
  p. 586, line 12, replace right by left.
Ch. 25
  p. 606, bottom diagram. On State 10, both labels on the loop
     should move R.