nstruction Set I
O CPU has built-in ability to execute a particular set of machine instructions, called its instruction set. O Most CPUs have 200 or more instructions (such as add, subtract, compare, etc.) in their instruction set. O CPUs made by different manufacturers have different instruction sets. O Manufacturers tend to group their CPUs into “families” having similar instruction sets. O New CPU whose instruction set includes instruction set of its predecessor CPU is said to be backward compatible with its predecessor.
Registers
O Special memory units, called registers, are used to hold information on a temporary basis as the instructions are interpreted and executed by the CPU. O Registers are part of the CPU (not main memory) of a computer. O The length of a register, sometimes called its word size, equals the number of bits it can store. O With all other parameters being the same, a CPU with 32-bit registers can process data twice larger than one with 16-bit registers.