Software named after the Muppet frog character in the children’s educational program, Sesame Street. Controls data exchanges between PCs and mainframe computers. It is an asynchronous file-transfer protocol, largely replaced by internet protocols (IP), but was once popular during the electronic bulletin board era. Automatic error detection and correction during transmission over ‘noisy’ telephone lines was its strength. Lack of speed was its weakness. Developed at Columbia University as an open source, non-proprietary and public domain, free software.