The assembler produces a listing of your source module, including any generated statements, and the object code assembled from the source module. You can control the form and content of the listing using assembler listing control instructions, assembler options, and user I/O exits. The listing control instructions are described in Assembler instruction statements, and in Processing statements. Assembler options and user I/O exits are discussed in the chapters "Controlling Your Assembly with Options" and "Providing User Exits" in the HLASM Programmer's Guide.

The assembler also prints messages about actual errors and warnings about potential errors in your source module.