Re: Code ?
Just google around for "Line Coding", lots of hits. It usually describes the logic representation of "0" and "1" bits.
There are other coding techniques other than line coding.
From a stream of raw data, you first carry out source (aka compressional) coding, then channel (aka error correction) coding, followed by line coding, then modulation. On the receiver end, you carry out the reverse.
As for RC5, I would term it more of a protocol than a code, normally used with remote controls.