Instruction Set

The set of machine instructions that a microprocessor recognizes and can execute – the
only language microprocessor knows
An instruction set includes low-level, a single step-at-a-time instructions, such as add,
subtract, multiply, and divide
 Each microprocessor family has its unique instruction set
Bigger instruction-sets mean more complex chips (higher costs, reduced efficiency), but
shorter programs
An  instruction set, or instruction set architecture (ISA), is a specification detailing the
commands that a computer's CPU should be able to understand and execute, or the set
of all commands implemented by a particular CPU design. The term describes the
aspects of a computer or microprocessor typically visible to a programmer, including the
native datatypes, instructions, registers, memory architecture, interrupt and fault system,
and external I/O (if any). "Instruction set architecture" is sometimes used to distinguish
this set of characteristics from the Micro-Architecture, which are the elements and
techniques used to implement the ISA, e.g. microcode, pipelining, cache systems, etc.
Bigger instruction-sets mean more complex chips (higher costs, reduced efficiency), but
shorter programs. Each microprocessor family has its unique instruction set. Following
are the few ISA;
MIPS  
Motorola 6800  
ARM  
PowerPC  
x86 (Pentium)  
ALGOL Object Code  
SPARC