Multiplication of a 2's-complement number by a known coefficient is often required in digital signal processing and other applications. When this is required to be performed on a microprocessor, an extension of Booth's algorithm (e.b.a.) can be used. Examples are presented to demonstrate how the multiplication is performed using e.b.a. on a microprocessor, and comparisons are made with the machine multiply instruction (m.m.i.) which show that the e.b.a. can take significantly less machine time.