UUcoding
UUcoding is a common method for transmitting binary files (I.e. non-text files) via e-mail. The method originated in the Unix community and was originally designed for ASCII text. The method involves two utilities. First, the UUencode utility encodes the files by converting 8-bit characters into 7-bit ASCII text for sending, and then the UUdecode utility decodes it back to its original format at the receiving end.
According to PC Magazine, "UUcoding was one of the first methods for sending binary files as attached files over Internet e-mail. Today, MIME is widely used."
On Apple computers, the same type of process is called BinHex.