Reed–Solomon error correction
QR codes use Reed–Solomon error correction over the finite field formula_1, the elements of which are encoded as bytes of 8 bits; the byte formula_2 with a standard numerical value formula_3 encodes the field element formula_4 where formula_5 is taken to be a primitive element satisfying formula_6. The Reed–Solomon code uses one of 37 different polynomials over formula_1, with degrees ranging from 7 to 68, depending on how many error correction bytes the code adds. It is implied by the form of Reed–Solomon used () that these polynomials are all on the form formula_8, however the rules for selecting the degree formula_9 are specific to the QR standard.