This thesis describes a set of computer program control structures which permits the application of certain structured programming techniques to the IBM/360 assembly language (ALC). The control structures are implemented by programmerdefined instructions known as macros. A history of computer software is presented, providing a basis for the emergence of structured programming. A survey of the major concepts of structured programming with special attention to control structures and their significance to structured programming follows. The macros developed in this study include DO, ENDDO, LEAVE, CASE, and ENDCASE. They provide a looping control structure, a loop-escape construct, and a selective control structure. Examples of usage are given.