A description in terms of generators and relations is given for the cohomology ring and the Hochschild cohomology ring of the group algebra for the even modular group over the ring of integers. The free resolution of the trivial module described by Wall is used for that. Moreover, the bimodule resolution of the group algebra in question is described. - See more at: http://www.ams.org/journals/spmj/2015-26-01/S1061-0022-2014-01328-3/#sthash.2f0yXV0f.dpuf