Biderivations of generalized matrix algebras

The aim of the paper is to give a description of biderivations for a certain class of generalized matrix algebras. We prove that under certain conditions a biderivation of a generalized matrix algebra is a sum of an extremal and an inner biderivation. We also consider the question when a biderivation of a generalized matrix algebra is an inner biderivation. As a consequence we show that every biderivation of a full matrix algebra over a unital algebra is inner.