In this section, we concentrate on the ARM processor. ARM is actually a family of RISC architectures that have been developed over many years. ARM does not manufacture its own chips; rather, it licenses its architecture to companies who either manufacture the CPU itself or integrate the ARM processor into a larger system.
The textual description of instructions, as opposed to their binary representation, is called an assembly language. ARM instructions are written one per line, starting after the first column. Comments begin with a semicolon and continue to the end of the line. A label, which gives a name to a memory location, comes at the beginning of the line, starting in the first column:
LDR r0,[r8] ; a comment
label ADD ...