1.1 Structure of this Manual
This manual is intended to describe what you need to know to use gnu as. We cover the syntax expected in source files, including notation for symbols, constants, and expressions; the directives that as understands; and of course how to invoke as.
This manual also describes some of the machine-dependent features of various flavors of the assembler.
On the other hand, this manual is not intended as an introduction to programming in assembly language—let alone programming in general! In a similar vein, we make no attempt to introduce the machine architecture; we do not describe the instruction set, standard mnemonics, registers or addressing modes that are standard to a particular architecture. You may want to consult the manufacturer's machine architecture manual for this information.