The earliest version of Punter supports only 7-bit transfers and uses a back-correction algorithm involving two checksums for failsafes.

The most noticeable part of the transmission is the report of status codes like ACK, GOO, BAD, and SYN for handshaking results.

Unlike modern computers, the C64 and C128 can poll the User Port (where the modem is interfaced) at slightly different baud rates and connection speeds.

C1 was the standard protocol for use on Commodore BBSes, and was rarely supported by terminal or BBS software for other operating systems.

Nevertheless, the protocol came into widespread use because Punter released the source code for the original implementation into the public domain.