Divisors of codeword weights

The exponent of a nonzero linear code over a finite field of characteristic p is the exponent in the highest power of p dividing the weights of all the codewords. If the code is a right ideal in a group algebra the exponent is related to invariant multilinear forms on the code. This expository paper presents recent results obtained from that relation, extending earlier work of Delsarte and McEliece.