Codes Defined by Forms of Degree 2 on Quadric Surfaces

In this correspondence, we study the functional codes C₂(X) defined on projective varieties X, in the case where X sub P³(F_q) is a 1-degenerate quadric or a nondegenerate quadric (hyperbolic or elliptic). We find the minimum distance of these codes, the second weight, and the third weight. We also show the geometrical structure of the first weight and second weight codewords. One result states that the codes C₂(X) defined on the elliptic quadrics are good codes according to the table of A. E. Brouwer.