Checksummer
Checksummer is a type-in program checker for Commodore used by the German magazines 64'er and Happy Computer.
To help readers by typewriting the program listings, at the begin of the year 1985 the little programming helpers MSE (Maschinenspracheeingabeeditor / Computer Code Editor / for Assembler-Listings) and Checksummer (Prüfsummenprogramm / to check the right BASIC-Codes) were published. In the next months the programming helpers were upgraded. Other German computer magazines published this helper-methods, too.
It produces a 000-255 checksum for each line.
Checksums V1 and V2 sum the bytes of the tokenized line including the line number as a 16-bit number, with the exception of all $20 (spaces), which are ignored. The low byte gives the checksum.
Checksummer V3 rolls each byte to the left by a certain number of bits before summing, starting with 0 bits at the first byte of the line, then each byte one bit more. Otherwise, the calculation corresponds to that of the older versions.
Sample Output
Links
- Info about 64'er and Checksummer
- German C64 wiki article about Checksummer
- Checksummer (64'er Jan 1985 pg 72)
- Checksummer 2.0 (64'er Mar 1985 pg 68)
- Checksummer 3.0 (64'er Apr 1985 pg 6)
- Javascript implementation of algorithm
