By “parallel programming” is meant the control of two or more operations which are executed virtually simultaneously, and each of which entails following a series of instructions. This can be brought about in a single computer either by equipping it with more than one control unit, or by allowing time-sharing of one control unit between several activities; the latter case seems of greater practical interest. Some of the advantages to be gained and some of the programming problems to be solved in putting these ideas into practice are discussed.