CHECK/CHECK2/CHECK3 - Revision history

JTN: /* Links */ missing punctuation

2026-02-19T15:44:17Z

‎Links: missing punctuation

JTN: /* Unofficial versions */ link to chek5sea.com

2026-02-19T15:43:42Z

‎Unofficial versions: link to chek5sea.com

JTN: /* Links */ link to typeins.tar.gz

2026-02-19T15:31:46Z

‎Links: link to typeins.tar.gz

JTN: s/After-market/Unofficial/

2026-02-19T14:40:48Z

s/After-market/Unofficial/

JTN: initial version without external links

2026-02-19T14:38:40Z

initial version without external links

New page

{{FormatInfo
|subcat=Error detection and correction
|released=July 1987
}}
'''CHECK/CHECK2/CHECK3''' was a Type-in Program Validator for (Mallard) [[BASIC]] program listings for the Amstrad PCW which were published in the UK's ''8000 Plus'' magazine (later renamed to ''PCW Plus'').

It generates one 4-hex-digit checksum for every line of program listing, case-insensitively and ignoring spaces. It operates on the ASCII (not tokenised) version of the listing.

== Version history ==
=== Original (buggy) version, 1987–1988 ===
The first version was published in issue 10 (July 1987) p60 of ''8000 Plus'' magazine (as a type-in BASIC listing). It was titled "BASIC Checker" and credited to Adrian Wilkins. All type-in listings in the magazine from this issue through issue 25 were accompanied by checksums generated by this program; the program itself was reprinted every few issues.

Unfortunately, this version was buggy -- while it would flag many mistakes, the checksum ignored every seventh character.

(John Elliott retrospectively refers to this version as 'check1'.)

=== CHECK2/3, 1988–1995 ===
A corrected version was published in issue 26 (November 1988) p64 under the name '''CHECK2.BAS'''; the correction was attributed to Peter Crane.

The checksums produced by this version were of course different from the first version. All type-in listings in the magazine from this issue through ''PCW Plus'' issue 106 (July 1995) were accompanied by these checksums.

(A third and last version of the checker, '''CHECK3.BAS''', was published in issue 43 (April 1990) pp60,63. There was no change to the checksum algorithm; the program just had more options for where to output the checksummed listing. This version was reprinted every few issues while checksummed listings were still being published.)

=== After-market versions ===
'''CHECK5''' (1994–5) by John Elliott extends the Mallard BASIC implementation to produce these checksums (compatible with CHECK2/3) directly, rather than having to save the program being keyed and feed it to a separate program. ("CHECK4" was an earlier attempt at the same thing by the same author.) 

== Sample output ==
This is an example of CHECK2 checksums.

[[File:8000_plus_pcw_basic_check2_sample.png|800px|alt=A dot-matrix printed program listing, with a column of checksums to the first. The first line is "140 check%=0 : j%=0" and has checksum "06BD".]]

== Links ==
* ''FIXME link to JCE's typeins.tar.gz on seasip.info'', a collection of all the type-in listings from ''8000/PCW Plus'', put together by John Elliott; the <tt>Checker</tt> directory contains all the versions of the BASIC checker program, a history, C versions, and the author's own CHECK5.

← Older revision		Revision as of 15:44, 19 February 2026
Line 31:		Line 31:

	== Links ==		== Links ==
−	* [https://www.seasip.info/Cpm/software/typeins.tar.gz typeins.tar.gz] (linked from [https://www.seasip.info/Unix/Joyce/index.html John Elliott's PCW page] is a collection of all the type-in listings from ''8000/PCW Plus''; the <tt>Checker</tt> directory contains all the versions of the BASIC checker program, a history, C versions, and the author's own CHECK5.	+	* [https://www.seasip.info/Cpm/software/typeins.tar.gz typeins.tar.gz] (linked from [https://www.seasip.info/Unix/Joyce/index.html John Elliott's PCW page]) is a collection of all the type-in listings from ''8000/PCW Plus''; the <tt>Checker</tt> directory contains all the versions of the BASIC checker program, a history, C versions, and the author's own CHECK5.

@@ Line 23: / Line 23: @@
 === Unofficial versions ===
-'''CHECK5''' (1994–5) by John Elliott extends the Mallard BASIC implementation to produce these checksums (compatible with CHECK2/3) directly, rather than having to save the program being keyed and feed it to a separate program. ("CHECK4" was an earlier attempt at the same thing by the same author.)  <!-- FIXME link to chek5sea.com on seasip.info -->
+'''CHECK5''' (1994–5) by John Elliott extends the Mallard BASIC implementation to produce these checksums (compatible with CHECK2/3) directly, rather than having to save the program being keyed and feed it to a separate program. ("CHECK4" was an earlier attempt at the same thing by the same author.)  It is downloadable as [https://www.seasip.info/Cpm/software/chek5sea.com chek5sea.com] ([[PMsfx]] self-extracting archive).
 == Sample output ==

← Older revision		Revision as of 15:31, 19 February 2026
Line 31:		Line 31:

	== Links ==		== Links ==
−	* ~~''FIXME link to JCE's~~ typeins.tar.gz on seasip.info'', a collection of all the type-in listings from ''8000/PCW Plus''~~, put together by John Elliott~~; the <tt>Checker</tt> directory contains all the versions of the BASIC checker program, a history, C versions, and the author's own CHECK5.	+	* [https://www.seasip.info/Cpm/software/typeins.tar.gz typeins.tar.gz] (linked from [https://www.seasip.info/Unix/Joyce/index.html John Elliott's PCW page] is a collection of all the type-in listings from ''8000/PCW Plus''; the <tt>Checker</tt> directory contains all the versions of the BASIC checker program, a history, C versions, and the author's own CHECK5.

@@ Line 22: / Line 22: @@
 (A third and last version of the checker, '''CHECK3.BAS''', was published in issue 43 (April 1990) pp60,63. There was no change to the checksum algorithm; the program just had more options for where to output the checksummed listing. This version was reprinted every few issues while checksummed listings were still being published.)
-=== After-market versions ===
+=== Unofficial versions ===
 '''CHECK5''' (1994–5) by John Elliott extends the Mallard BASIC implementation to produce these checksums (compatible with CHECK2/3) directly, rather than having to save the program being keyed and feed it to a separate program. ("CHECK4" was an earlier attempt at the same thing by the same author.)  <!-- FIXME link to chek5sea.com on seasip.info -->