CPU (Central Processing Unit)

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Description

• It's a microprocessor chip developed by Intel, AMD or any other company.
• CPU speed depends upon the clock frequency, higher the clock frequency more number of instructions can be executed per second.
• Clock frequency is measured in MHz or GHz.
• CPU word size is the largest number of bits that can be handled by CPU in one clock cycle. It is either 8, 16, 32, 64 or 128 bit.
• This word size value determines number of bit processor i.e. 8-bit processor, 16-bit processor, 32 bit processor etc.
• CPU performance also depends upon the RAM, bus speed and cache size as well.
• Called as heart of the computer.

Block diagram

Working:

• CPU consists of three basic units: control unit, Arithmetic Logical Unit (ALU) and memory unit.
• Input is given through the input devices to CPU.
• Control unit controls communication within ALU and memory unit.
• Decides which circuit is to be activated.
• For reading instruction it uses Fetch-execute mechanism.
• Control unit gets instruction from memory.
• Control unit decides what to do of that instruction and transfers it to the ALU.
• ALU performs various arithmetic operations like addition, subtraction, multiplication, division and logical operations like AND, OR, NOT, NAND etc. on that instruction.
• Results of ALU are stored in the memory or resistor for its further operations.
• After completing the instruction, stored results are passed to the output devices.
• To synchronize all these operations CPU uses its own system clock.

What it does?

• Executes stored instructions called as program.
• Tells rest of the computer system what to do.
• Executes arithmetic calculation and data manipulation.
• Holds data and instruction which are in the current use.
• Responsible for storing and retrieving information on disks and other media.

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