The Automatic Proofreader
Encyclopedia
The Automatic Proofreader is a series of checksum
utilities published by COMPUTE! Publications for its COMPUTE!
and COMPUTE!'s Gazette
magazines, and various books. These programs were designed to allow home computer
users to easily detect errors on BASIC type-in program
s, and worked by displaying a hash value
for each line entered that could be compared against the reference value printed in the magazine. Initially published for use with the Commodore 64
and VIC-20
, the Proofreader was later made available for the Atari 8-bit family
, Apple II family, and IBM PC
/PCjr
as well.
The line-individual "real-time" feedback feature was something of a novelty at the time, and represented a significant improvement over earlier checksum utilities, which were typically run only after a user program had been entered, most often giving a single control value for the entire program. The majority of such schemes lacked an error location feature, and, due to quite simplistic checksum algorithms, had serious trouble catching many "minor" typing errors like transposed characters (these errors having the potential of being just as detrimental as "major" ones to the typed-in program's functioning).
-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 spacing 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 with a letter pair.
The New Automatic Proofreader was designed to run on any Commodore 8-bit
home computer (including the C16
/Plus/4
and C128
), 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.
Checksum
A checksum or hash sum is a fixed-size datum computed from an arbitrary block of digital data for the purpose of detecting accidental errors that may have been introduced during its transmission or storage. The integrity of the data can be checked at any later time by recomputing the checksum and...
utilities published by COMPUTE! Publications for its COMPUTE!
COMPUTE!
Compute! was an American computer magazine that was published from 1979 to 1994, though it can trace its origin to 1978 in Len Lindsay's PET Gazette, one of the first magazines for the Commodore PET computer. In its 1980s heyday Compute! covered all major platforms, and several single-platform...
and COMPUTE!'s Gazette
COMPUTE!'s Gazette
COMPUTE!'s Gazette was a computer magazine of the 1980s, directed at users of Commodore's 8-bit home computers. Publishing its first issue in July 1983, the Gazette was a Commodore-only daughter magazine of the computer hobbyist magazine COMPUTE!....
magazines, and various books. These programs were designed to allow home computer
Home computer
Home computers were a class of microcomputers entering the market in 1977, and becoming increasingly common during the 1980s. They were marketed to consumers as affordable and accessible computers that, for the first time, were intended for the use of a single nontechnical user...
users to easily detect errors on BASIC type-in program
Type-in program
A type-in program, or just type-in, is a computer program listing printed in a computer magazine or book, meant to be typed in by the reader in order to run the program on a computer....
s, and worked by displaying a hash value
Hash function
A hash function is any algorithm or subroutine that maps large data sets to smaller data sets, called keys. For example, a single integer can serve as an index to an array...
for each line entered that could be compared against the reference value printed in the magazine. Initially published for use with the Commodore 64
Commodore 64
The Commodore 64 is an 8-bit home computer introduced by Commodore International in January 1982.Volume production started in the spring of 1982, with machines being released on to the market in August at a price of US$595...
and VIC-20
Commodore VIC-20
The VIC-20 is an 8-bit home computer which was sold by Commodore Business Machines. The VIC-20 was announced in 1980, roughly three years after Commodore's first personal computer, the PET...
, the Proofreader was later made available for the Atari 8-bit family
Atari 8-bit family
The Atari 8-bit family is a series of 8-bit home computers manufactured from 1979 to 1992. All are based on the MOS Technology 6502 CPU and were the first home computers designed with custom coprocessor chips...
, Apple II family, and IBM PC
IBM PC
The IBM Personal Computer, commonly known as the IBM PC, is the original version and progenitor of the IBM PC compatible hardware platform. It is IBM model number 5150, and was introduced on August 12, 1981...
/PCjr
IBM PCjr
The IBM PCjr was IBM's first attempt to enter the home computer market. The PCjr, IBM model number 4860, retained the IBM PC's 8088 CPU and BIOS interface for compatibility, but various design and implementation decisions led the PCjr to be a commercial failure.- Features :Announced November 1,...
as well.
The line-individual "real-time" feedback feature was something of a novelty at the time, and represented a significant improvement over earlier checksum utilities, which were typically run only after a user program had been entered, most often giving a single control value for the entire program. The majority of such schemes lacked an error location feature, and, due to quite simplistic checksum algorithms, had serious trouble catching many "minor" typing errors like transposed characters (these errors having the potential of being just as detrimental as "major" ones to the typed-in program's functioning).
Commodore versions
The Automatic Proofreader was first introduced in October 1983 for the Commodore 64 and VIC-20. The same listing was designed to work on both systems. This version of the Proofreader would display a byteByte
The byte is a unit of digital information in computing and telecommunications that most commonly consists of eight bits. Historically, a byte was the number of bits used to encode a single character of text in a computer and for this reason it is the basic addressable element in many computer...
-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
Datassette
The Commodore 1530 Datasette , was Commodore's dedicated computer tape drive.It provided access to an inexpensive storage medium for Commodore's 8-bit home/personal computers, notably the PET, VIC-20, and C64...
. 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
Transpose
In linear algebra, the transpose of a matrix A is another matrix AT created by any one of the following equivalent actions:...
errors, nor did it take whitespace
Whitespace (computer science)
In computer science, whitespace is any single character or series of characters that represents horizontal or vertical space in typography. When rendered, a whitespace character does not correspond to a visual mark, but typically does occupy an area on a page...
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 spacing 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 with a letter pair.
The New Automatic Proofreader was designed to run on any Commodore 8-bit
8-bit
The first widely adopted 8-bit microprocessor was the Intel 8080, being used in many hobbyist computers of the late 1970s and early 1980s, often running the CP/M operating system. The Zilog Z80 and the Motorola 6800 were also used in similar computers...
home computer (including the C16
Commodore 16
The Commodore 16 was a home computer made by Commodore with a 6502-compatible 8501 CPU, released in 1984. It was intended to be an entry-level computer to replace the VIC-20 and it often sold for 99 USD...
/Plus/4
Commodore Plus/4
The Commodore Plus/4 was a home computer released by Commodore International in 1984. The "Plus/4" name refers to the four-application ROM resident office suite ; it was billed as "the productivity computer with software built-in"...
and C128
Commodore 128
The Commodore 128 home/personal computer was the last 8-bit machine commercially released by Commodore Business Machines...
), 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
Disk magazine
A disk magazine, colloquially known as a diskmag, is a magazine that is distributed in electronic form to be read using computers. These had some popularity in the 1980s and 1990s as periodicals distributed on floppy disk, hence their name...
after the December 1993 issue.