Uuencoding

Content sourced from Wikipedia, licensed under CC BY-SA 3.0.

Uuencoding is an old Unix method for turning binary data into readable text so it can travel safely through email and Usenet. It uses a 6‑bit scheme, turning every 3 bytes into 4 printable ASCII characters. Each line of encoded data starts with a character that indicates how many bytes were encoded on that line (the value is 32 plus the byte count; a line with zero bytes uses a backtick). Most lines carry 45 bytes of data, which becomes 60 encoded characters. A file is sent with a begin line like "begin 644 filename", followed by the encoded lines, and ends with an end marker. To decode, uudecode reverses the process: it converts each group of four encoded characters back into 3 bytes. Uuencoding was popular for sending binary attachments by email and on Usenet, but it has largely been replaced by MIME with Base64. Many programming languages still support uuencoding, but Base64 and other formats are now standard.