In a single-parity-check code, a single parity bit is appended to a block of k message bits (m₁, m₂,,.., m_k,). The single parity bit b1 is chosen so that the code word satisfies the even parity ride:

m₁ + m₂ + . . . + m_k + b₁ = 0, mod 2 for k = 3, set up the 2k possible code words in the code defined by this rule.