F64Summer

F64Summer by Felix Palmen (aka Zirias) is a type-in program checker for Commodore used by the German-language mazine Weihnachten auf dem Commodore (Christmas on the Commodore), a joint project by Christian Gleinser (aka ZeHa) and Forum64 members.

It displays a four-digit checksum for each entered line

Version 2 was released in November 2019, which can now optionally ignore comments in the program (REM commands) when creating checksums and when entering them.

It uses a 16-bit Galois LFSR. Spaces outside strings are ignored. Checksum is created after tokenization, so equivalent commands like PRINT and ? are treated the same.

For each character read, an inner loop iterates over all 8 bits. The LFSR is shifted once with feedback for each bit, but the output bit is also XORed with the respective bit of the character currently being processed before the feedback.

There are currently 4 different variants of the F64Summer that can be run on VC20, C64 , C16 / C116 / Plus/4 and C128. There is also a 32-bit Windows application "mksums.exe" with which the creator of a listing can calculate the checksums for all lines of a BASIC file in PRG format. These checksums can then be combined with the listing to be printed. The source is also available to be ported to any platform

Sample Output

Links

• CSDb
• Plus/4 World
• German C64 wiki article
• English C64 wiki article
• Release thread on Forum64.de (Includes details on how algorithm works)
• Source on github
• Youtube video of F64Summer in action