Introduction
A computer can understand and interpret only machine language. Machine language is in binary form and, thus, difficult to write. The assembler language is a symbolic programming language that you can use to code instructions instead of coding in machine language.

Your program, written in the assembler language, is the source module that is input to the assembler. The assembler processes your source module and produces an object module in machine language (called object code). The object module is input to be processed by the linker or the binder. The linker or binder produces a load module (z/OS® and CMS), or a phase (z/VSE®), that the computer can load into its memory and run. Your source module and the object code produced are printed, along with other information, on a program listing.