B protocol
The B protocol, or CIS B, is a file transfer protocol developed for the CompuServe Information Service, and implemented in 1981. The protocol was later expanded in the QuickB version (which was an asynchronous version of the standard protocol) and later the enhanced B Plus version. It was a fairly advanced protocol for its era, supporting efficient transfers of files, commands and other data as well, and could be used in both directions at the same time in certain modes. These advanced features were not widely used, but could be found in a small number of client-side packages. Since B protocol was designed only to work within the CompuServe, most third-party communications clients of the day were not compatible with it. Notable exceptions were Tera Term and Datastorm's ProComm Plus on the PC which featured the ability to listen for the command on the active communications port, and ZTerm on the Mac which allowed auto-starting transfers. This development was part of a wider trend of using external communications applications in conjunction with online services. Description The original version of the B Protocol was an outgrowth of an earlier bi-directional protocol introduced in 1979, adding options for including a standardized command