The Automatic Proofreader was first introduced in October 1983 for the Commodore 64 and VIC-20. 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. The initial version of the Proofreader, however, had several drawbacks. It was loaded into the cassette buffer (memory area), which was overwritten whenever a program was loaded or saved using the
Datassette. 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. Also, the checksum method used was relatively rudimentary, and did not catch
transposition errors, nor did it take
whitespace into account. Because of this, the
New Automatic Proofreader was introduced in February 1986. This version used a more sophisticated checksum algorithm that could catch transposition errors. It also took spaces into account if they were within quotes (where they were generally significant to the program's operation), while ignoring them outside of quotes (where they were not relevant). Also, the decimal display of the checksum was replaced by two letters. The New Automatic Proofreader was designed to run on any Commodore
8-bit home computer (including the
Commodore 16,
Plus/4, and
Commodore 128), automatically relocating itself to the bottom of BASIC
RAM and moving pointers to hide its presence. It was continuously published until ''COMPUTE!'s Gazette'' switched over to a
disk-only format after the December 1993 issue. ==References==