Editing Block code (section)

=== Popular notation ===
The notation <math>(n,k,d)_q</math> describes a block code over an alphabet <math>\Sigma</math> of size <math>q</math>, with a block length <math>n</math>, message length <math>k</math>, and distance <math>d</math>.
If the block code is a linear block code, then the square brackets in the notation <math>[n,k,d]_q</math> are used to represent that fact.
For binary codes with <math>q=2</math>, the index is sometimes dropped.
For [[maximum distance separable code]]s, the distance is always <math>d=n-k+1</math>, but sometimes the precise distance is not known, non-trivial to prove or state, or not needed. In such cases, the <math>d</math>-component may be missing.

Sometimes, especially for non-block codes, the notation <math>(n,M,d)_q</math> is used for codes that contain <math>M</math> codewords of length <math>n</math>. For block codes with messages of length <math>k</math> over an alphabet of size <math>q</math>, this number would be <math>M=q^k</math>.