Editing Block code (section)

=== The rate ''R'' ===
The '''rate''' of a block code is defined as the ratio between its message length and its block length:
:<math>R=k/n</math>.
A large rate means that the amount of actual message per transmitted block is high. In this sense, the rate measures the transmission speed and the quantity <math>1-R</math> measures the overhead that occurs due to the encoding with the block code.
It is a simple [[information theory|information theoretical]] fact that the rate cannot exceed <math>1</math> since data cannot in general be losslessly compressed. Formally, this follows from the fact that the code <math>C</math> is an injective map.