Type IV codes over a non-local non-unital ring.

There is a local ring H of order 4, without identity for the multiplication, defined by generators and relations as H =(a, b I 2a = 2b = 0, a2 = 0, b2 = b, ab = ba = 0). We classify self orthogonal codes of length n and size 2„ (called here quasi self-dual codes or QSD) up to the length n = 6. In particular, we classify quasi Type IV codes (a subclass of Type IV codes, viz QSD codes with even weights) up to n = 6. [ABSTRACT FROM AUTHOR]