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Created page with "{{FormatInfo |subcat=Error detection and correction |released=1985 }} '''Verifizer''' is a type-in program checker for Commodore used by Transactor magazine. There were five ..."

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{{FormatInfo
|subcat=Error detection and correction
|released=1985
}}
'''Verifizer''' is a type-in program checker for Commodore used by Transactor magazine.

There were five separate versions for PET/CBM, VIC/C64, Plus 4, C128, and B128.

Verigen is the companion program to create program listings.

Every time you press RETURN on a program line, a two-letter report code will appear on the top left of the screen that can be matched against the code in the listing.

It uses a 'weighted checksum technique' that will catch transposition errors but can be fooled if you try hard enough (transpose two sets of 4 characters). The weights 1,2,3,4 are assigned to the tokenised BASIC line, and the low byte of the line number is added in. In other words, a checksum is obtained by taking the line number low byte, adding 1 times the first byte in the BASIC line, 2 times the second, 3 times the third, 4 times the fourth, the 1 times the fifth, etc. The final checksum is a two byte unsigned integer. The high byte is discarded, and the low and high nybbles of the low byte are used to form the two report code characters. Since only the low byte is used, checksum variances of exact multiples of 256 will not be detected.

It ignores spaces and standard keywords (like nE instead of next) will not affect the report code.

== Sample Output ==
[[File:Verifizer.jpg]]

== Links ==
* [https://archive.org/details/transactor-magazines-v5-i06/page/n11/mode/2up Verifizer for C64/VIC20 and PET/CBM, Verigen] (Transactor May 1985 pg 11)
* [https://archive.org/details/transactor-magazines-v6-i05/page/n5/mode/2up Verifizer for Tape mod] (Transactor Mar 1986 pg 5)
* [https://archive.org/details/transactor-magazines-v6-i06/page/n5/mode/2up Double Verifizer mod] (Transactor May 1986 pg 5)
* [https://archive.org/details/transactor-magazines-v7-i01/page/n13/mode/2up Verifizer for Plus 4 and C128 40 col mode] (Transactor Jul 1986 pg 11)
** [http://plus4world.powweb.com/software/Verifizer Verifizer +4 at Plus/4 World]
* [https://archive.org/details/transactor-magazines-v7-i03/page/n7/mode/2up Verifizer for Tape, C128 40 and 80 col mode, B128] (Transactor Nov 1986 pg 4)
** [https://archive.org/details/transactor-magazines-v7-i05/page/n5/mode/2up alt copy with better typography] (Transactor Mar 1987 pg 4)
* [https://archive.org/details/transactor-magazines-v9-i01/page/n5/mode/2up Updated Verifizer for C128] (Transactor Sep 1988 pg 4)
* [https://diskmaster.textfiles.com/browse/26749/Transactor_03_1985_Transactor_Publishing.d64 Verifizer +4, c128, pet, vic/64 in d64 format] ([https://archive.org/details/Transactor_03_1985_Transactor_Publishing backup])
* [https://diskmaster.textfiles.com/browse/26749/Transactor_05_1985_Transactor_Publishing.d64 Verigen in d64 format] ([https://archive.org/details/Transactor_05_1985_Transactor_Publishing backup])
* [https://diskmaster.textfiles.com/browse/26749/Transactor_09_1986_Transactor_Publishing.d64 Verifizer c128 40/80 col mode, b128 in d64 format] ([https://archive.org/details/Transactor_09_1986_Transactor_Publishing backup])
* [https://diskmaster.textfiles.com/browse/26749/Transactor_27_1988_Transactor_Publishing.d64 Verifizer c128 updated in d64 format] ([https://archive.org/details/Transactor_27_1988_Transactor_Publishing backup])

Verifizer - Revision history

Parchivist: Created page with "{{FormatInfo |subcat=Error detection and correction |released=1985 }} '''Verifizer''' is a type-in program checker for Commodore used by Transactor magazine. There were five ..."