CPU Register

• Registers are high speed storage areas within the CPU, But have least storage capacity. Registers are not referenced by their address,but are directly accessed and manipulated by the CPU during instruction execution. 
• Register store data, instructions, addresses and intermediate results of processing. Registers are often referred to as the the CPU working Memory. 
• The data and instructions that require processing much be brought in the registers of CPU before they can be processed. For example if two number are be added, both numbers are brought in registers, added and the result is also placed in a register. 
• Register are used for different purposes, with each register serving a specific purpose. 

• Accumulator (AC) stores the results of arithmetic and logic operations. 
• Instruction Register (IR) contains the current instructions most recently fetched. 
• Program Counter( PC) contains the address of next instruction to be processed.
• Memory Address Register (MAR) contains the address of next location memory to be accessed.
• Memory Buffer Register ( MBR) it contains temporarily stores data from memory or the data to be sent to memory.
• Data Register (DR) it sore the operands and any other data. 

Some Basic Characteristics of CPU Registers

• The Number of registers and the size of each register in a CPU helps to determine the power and the speed of a CPU.
• The overall number of registers can very from ten to many hundreds, depending on the type and complexity of the processor.  
• The size of register, also word size. 
• 32 bit processor and 64 bit processor are the terms used to refer to the size of the register . Other factors remaining the same, 64 bit processor can process the data twice as fast as one with 32 bit processor.