This chapter introduces a sample of the more common instruction formats and provides general rules for coding them in their symbolic assembler language format.

For the complete specifications of machine instructions, their object code format, their coding specifications, and their use of registers and virtual storage areas, see the applicable z/Architecture Principles of Operation manual for your processor. If your program requires vector facility instructions, see the applicable Vector Operations manual for the complete specifications of vector-facility instructions.

At assembly time, the assembler converts the symbolic assembler language representation of the machine instructions to the corresponding object code. The computer processes this object code at execution time. Thus, the functions described in this section can be called execution-time functions.

Also at assembly time, the assembler creates the object code of the data constants and reserves storage for the areas you specify in your data definition assembler instructions, such as DC and DS (see Assembler instruction statements). At execution time, the machine instructions can refer to these constants and areas, but the constants themselves are not normally processed.

Each is discussed in the following sections.