Component of CPU-Control Unit- Arithmetic Logic Unit- Memory Unit

Component of CPU-Control Unit- Arithmetic Logic Unit- Memory Unit

Introduction:

A CPU or Central Processing Unit is the heart of a computer and is installed in a socket specified on a motherboard. CPU generally performs the arithmetical and logical operations, controlling of different input-output devices. These operations are performed based on some predefined algorithms and instructions normally referred as computer programs. A computer program is a set of instructions written by a human to perform a specific operation by the CPU. A computer program is normally stored in the memory unit of the Central Processing Unit.

The CPU has  3 components .

A. CU(Control Unit):

Directs different parts of the computer to carry out instructions. It controls communication and coordination between input/output devices.

1. Control Unit’s main function in CPU to process data.

2.The Control Unit extracts instructions from memory and decodes and executes them.

3.Manages all resources of a computer

4.Manages a 4-step basic operation which is called a machine cycle or processing cycle.

Machine Cycle

• 4 step in Machine Cycle :

• Step 1:Fetch – retrieve an instruction from memory

• Step 2:Decode – translate instruction in a form ALU can understand (command )

• Step 3:Execute – Carry out instruction

• Step 4:Store – copy results to Memory

B. ALU(Arithmetic Logic Unit):

Performs all arithmetical calculations such as addition and multiplication & makes all logical decisions.

• An arithmetic logic unit (ALU) is one of the core components of all central processing units.

• Arithmetic operations: e.g., add, subtract, multiply, divide, square root, cosine, etc.

• Logical operations: e.g., compare two numbers to see which is greater, check whether a true/false statement is true, etc.

• Comparison operation : e.g:AND, OR, NOT, NAND, NOR, XOR and equacalence (=)

C. MU : Memory Unit/ Register set:

1. Memory locations are needed for storing pointers,

counters, return addresses, temporary results, and partial products during multiplication.

2. As memory access is time consuming process better to have those values in processor registers.

3. To have a large nos of registers, it have to connected with a common bus system.

It will be part of various micro-operation like arithmetic, logic and shift operation in the processor.