U Uencode Usage To Transfer Binary
| Field | Communications - transferring files over text-based systems |
| Went Obsolete | Approximately 1997 |
| Made Obsolete By | More advanced MIME-capable email systems |
| Knowledge Assumed | Moderate familiarity with email |
| When useful | If you're stuck using a really old system to access the internet…. |
UUEncoding? (and the corresponding UUDecoding?) is the act of taking a binary file (anything non-text, so an image or executable or sound clip for example), and converting it to 7-bit ASCII text. Why? In 'the olden days' systems such as email and NNTP assumed you'd only ever want to send text, and even then no 'special' characters were allowed for. This is known as 7-bit ASCII and is capable of recognising 128 different characters. Notable omissions include the british pound sign (�). Trying to send a binary file would result in corruption of the data and mangling of the recipients inbox.
The way around this was to UUEncode? the binary file, which simply converts the regular 8-bit-to-a-byte binary file into blocks of 7 bits, each of which is viewable as a readable character. This can be then sent over email or NNTP, run through a UUDecoder? the other end which converts back to 8-bit binary, and the job is done.
UUEncoded? files can be recognised by the header “begin 644 filename.ext” which is the filename that the file will be given once decoded.
