How to write conditional assembly instructions

This chapter describes the conditional assembly language. With the conditional assembly language, you can carry out general arithmetic and logical computations, and many of the other functions you can carry out with any other programming language. Also, by writing conditional assembly instructions in combination with other assembler language statements, you can:

Select sequences of these source statements, called model statements, from which machine and assembler instructions are generated
Vary the contents of these model statements during generation

The assembler processes the instructions and expressions of the conditional assembly language during conditional assembly processing. Then, at assembly time, it processes the generated instructions. Conditional assembly instructions, however, are not processed after conditional assembly processing is completed.

The conditional assembly language is more versatile when you use it to interact with symbolic parameters and the system variable symbols inside a macro definition. However, you can also use the conditional assembly language in open code; that is, code that is not within a macro definition.