101
013
The telegraph operator (or theorist, or compression algorithm) must pay attention to the whole message. Nonetheless, the extra information is minimal; the message can still be compressed, wherever pattern exists. We may say it contains a redundant part and an arbitrary part.
It was Shannon who first showed that anything nonrandom in a message allows compression:
F: 101
101
0111
1011
0110
1011
1010
1110
1111
0100
1110
1101
0011
1101
110