Dear GAP-Forum,

E.Freitag asks about the availability of O(d,q) in GAP.
In GAP 3 one can use the shared package matrix,
where they are defined. Do
RequirePackage("matrix");
g:=O(w,n,q);

Here
w is the Witt index, n is dimension, and q is field size.

Hope this helps,
Dmitrii