REP : Repeat Instruction Prefix :-
This instruction is utilized as a prefix to other instructions. The instruction in which the REP prefix is provided, is executed repetitively till the CX becomes zero (at each iteration registration CX is automatically decremented by one). When the register CX value will be zero, the execution proceeds to the next instruction sequentially. There are 2 more choice of the REP instruction. The first is REPE/REPZ, for example. Repeat operation while zero/equal. The second is REPNE/REPNZ permit for repeating the operation while not zero/not equal. These choices are utilized as instruction prefixes for CMPS, SCAS instructions only.