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Definitions and Functions of Central Processing Unit (CPU)

Processor is a crucial component of computer system. It is a small chip found inside the system unit. A computer must have this component to run system. Now we discuss below about it’s definition, means and function.


Processor or microprocessor is a microchip installed on the specific slot of motherboard. It is also known asProcessor central processing unit shortly CPU. It takes input from input devices, process data or instruction which is provided by user and finally output the results on the output devices. All processing task is performed by this. So, it is called the Brain of a computer. The heat sink and cooling fan set upper position of CPU are used to keep cold it.

Internal Elements:

Microprocessor holds three basic element in itself. They are ALU, CU, memory. All arithmetic and logical operation is performed by arithmetic logic unit shortly ALU. The control unit, CU is responsible to manage various components of the system. This calls the ALU to do necessary calculations. Memory stores data to process.


There are four primary function of a CPU described below the steps:

  1. Fetch: Each instruction or data is stored in memory address. The processor takes the memory address and fetch data from the program counter.
  2. Decode: In the step, all data are decoded into CPU understandable binary format.
  3. Execute: Three things are done to execute instructions. First it performs arithmetical calculations by its ALU, then move data one memory address to another based on instructions.
  4. Store: In this last step, processed data are written into memory.

Note: The CPU speed is measured by Hertz.


The old microprocessor had many pins. But the modern one has no pin. Today it looks like small, square, rounded, pinless and with metallic connectors installed on CPU socket of system board.


Many companies are manufacturing microprocessor all over the world today. The top ranked companies are Intel, AMD, IBM, NVIDIA, Motorola, Hewlett-Packard (HP), Acer, Sun Microsystems, Qualcomm, Via, Ti etc.

Historical Background:

Intel Corporation has started their journey from 18th July, 1968 by Robert Noyce, Gordon Moore and Andrew Grove. They have introduced the first microprocessor named Intel 4004 dated on 15th November, 1971 by taking the help of Ted Hoff. The 4004 holds 2300 transistors and also capable to perform 60,000 task per second. Its cost was $200. Then they have changed their technologies day by day. In April 1, 1972 the Intel 8008 has been produced. Then they have changed for few years and released the following sequence-

8080 in April 1, 1974

8085 in March, 1976

8086 in June 8, 1976

8088 in June 1, 1979

80286 in February 1, 1982

80386 in October, 1985

SUN introduced the first SPARC processor in 1987.

Intel has published their 80386SX in 1988.

AM386 microprocessor family has been populated by AMD on March-1991.

Intel introduces Pentium in 1993 and Xeon in 1998, Celeron in 1999.

AMD releases first Dual-core in 2005, Intel provides Core 2 Duo in 2006 and Core i7 desktop processor in 2008.

Currently they are improving their CPU technology analyzing its speed.

What is Clock Speed?

The clock speed is a CPU speed measurement unit measured by Gigahertz(GHz). This is the number of how many instructions or data can be processed in a given second.


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