Instruction Set Architecture (ISA) 

The collection of assembly/machine instruction set of the machine and the machine resources (memory and programmer-accessible registers) that can be managed with these instructions is called Instruction Set Architecture ( ISA ). An Assembly programmer must understand the ISA of the specific machine he is writing codes for in order to write correct programs.

Fig. m010133.1 shows a few examples of the ISA of several machines.

Fig. m010133.1 The ISA of several machines