General Architecture of a Computer

A computer is a programmable device that accepts data as input and process it with a set of instructions and produces the result as output.

A computer consists of the following four parts,

1. Input Unit.
2. Output Unit.
3. Memory Unit.
4. Central Processing Unit.

Input Unit

• The input unit accepts data and instructions from user.
• Digitise received data.
• Supply digitised data to computer system for processing.

Output Unit

• Accept processed data from computer.
• Convert binary data to humanely acceptable form.
• Supply this result to user.

Memory

• Store data to be processed by the system.
• Store Intermediate result.
• Store final result.

Central Processing Unit

• The CPU retrieves and executes all the instructions of a computer program.
• It consist of
  • Arithmetic and Logic Unit (ALU).
  • Control Unit.
  • Registers.

Arithmetic Logic Unit

• The ALU performs all arithmetic and logical operations.

Registers

• These are the temporary storage location within the CPU.
• The CPU uses several types of registers for specific functions.
• Eg: Accumulator, PC, IR, etc.

Control Unit

• The control unit controls and coordinates entire computer system.
• Fetches instruction from memory.
• Decodes the instruction.
• Execute the instruction.
• Control data transfer between memory and I/O devices.

Buses

• Common communication path.
• Physical group of signal lines that have a related function.
• Allows transfer of electrical signals between different components.
• Most used bus architecture is the three bus architecture. (Data bus, Address bus, Control bus)