The Automatic Proofreader is a series of checksum utilities published by COMPUTE!
[5] This version of the Proofreader would display a byte-sized numeric value at the top left corner of the screen whenever a program line was entered.
This caused difficulties if a cassette user had to resume work on a partially completed listing.
A complicated method had to be used to get both the Proofreader and the program listing in memory at the same time.
[6] Also, the checksum method used was relatively rudimentary, and did not catch transposition errors, nor did it take whitespace into account.