Block code

In information theory, a block code is a code which encodes strings formed from an alphabet set ${\displaystyle S}$ into code words by encoding each letter of ${\displaystyle S}$ separately. Let ${\displaystyle (k_{1},k_{2},\ldots ,k_{m})}$ be a sequence of natural numbers each less than ${\displaystyle |S|}$. If ${\displaystyle S={s_{1},s_{2},\ldots ,s_{n}}}$ and a particular word ${\displaystyle W}$ is written as ${\displaystyle W=s_{k_{1}}s_{k_{2}}\ldots s_{k_{m}}}$, then the code word corresponding to ${\displaystyle W}$, namely ${\displaystyle C(W)}$, is

${\displaystyle C(W)=C(s_{k_{1}})C(s_{k_{2}})\ldots C(s_{k_{m}})}$.