AnSTRACT. Let G = GLn(Fq) be the finite general linear group and let M = M,(Fq) be the monoid of all n x n matrices over Fq. Let B be a Borel subgroup of G, let W be the subgroup of permutation matrices, and let ~ D W be the monoid of all zero-one matrices which have at most one non-zero entry in each row and each column. The monoid ~ plays the same role for M that the Weyl group W does for G. In particular there is a length function on ~ which extends the length function on W and a C-algebra Hc(M, B) which includes lwahori's 'Hecke algebra' Hc(G, B) and shares many of its properties.
Added in proof.Concerning the remarks which precede Theorem 4.41 and the related footnote: About a week ago Putcha informed me that there is a gap in my argument for the semisimplicity of C [M]. Thus, at this writing, the only proof of semisimplicity is the one by Oknifiski and Putcha.