Chapter 5: Procedures and Units

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5.1 Chapter Overview

In a procedural programming language the basic unit of code is the procedure. A procedure is a set of instructions that compute some value or take some action (such as printing or reading a character value). The definition of a procedure is very similar to the definition of an algorithm. A procedure is a set of rules to follow which, if they conclude, produce some result. An algorithm is also such a sequence, but an algorithm is guaranteed to terminate whereas a procedure offers no such guarantee.

This chapter discusses how HLA implements procedures. It begins by discussing HLA's high level syntax for procedure declarations and invocations, but it also describes the low level implementation of procedures at the machine level. At this point, you should be getting comfortable with assembly language programming, so it's time to start presenting "pure" assembly language rather than continuing to rely on HLA's high level syntax as a crutch.