page 259 line 8: add period after frame buffer
page 263 line below equation: change 
to 
page 263 items 3 and 4: change && to &
page 263 item 3 delete word logical
page 280 last equation 
page 284 last line of first paragraph in Section 7.8: screen coordinates
not window coordinates
page 288 third equation, change + to -: 
page 288 last equation, top line next to brace change 
to 
page 294 second line of second paragraph: replace claws with teeth