What is Computer Architecture?

John Von Neumann Architecture:

In 1945, mathematician John Von Neumann and his colleagues proposed an internal design of an electronic computer. This design is called Von Neumann architecture. The computer based on this architecture is called stored program machine. The stored program machine consists of the following units:

  1. a unit that performs calculations,
  2. a unit that controls the sequence of operations,
  3. a storage that holds data and program, and
  4. Input and output units.

According to this design, instructions are stored in the storage (memory) of the computer. The computer reads the instructions one by one and executes them accordingly. This was a simple design. But it proved very powerful. Most computers from that time until today are based on this design.


Architecture of Computer System:

Computer architecture can be divided into following components:-

  1. Input / Output
  2. Storage
  3. Communication
  4. Control
  5. Processing

The rules and methods to describe the functionality and implementation of the computer systems are called Computer Architecture. The most important components of a stored program machine are:


The processor also called the central processing unit or CPU. It is a small chip inside the computer. CPU controls the other parts of the computer. It makes decisions and calculations. CPU executes instructions that operate the computer. It contains two units namely control unit and an arithmetic logic unit (ALU).

Control Unit:

Control Unit makes meaningful decisions and sends the signals to other parts of the Computer. Control Unit reads instructions from the memory. It decodes each instruction and uses other components of the computer system to execute these instructions.

Arithmetic Logic Unit:

This unit performs arithmetic, comparison and logic operations. ALU is a digital electronic circuit performing logical and arithmetic operations.

Main Memory (Random Access Memory):

Memory consists of electronic components that store instructions which are executed by the processor and the data needed by these instructions. Main memory is also known as RAM (Random Access Memory). It needs electronic power to maintain information. Due to switching off the power, the information will be lost. It also holds the results of processing. Since computer system works with data and instructions by storing them in the main memory. The main memory is also known as the working area of the computer.


Input / Output:

Input / Output are the communication system in a computer. The signals or data received by the system is called input and data or signals sent by the system is called output. Input Output devices are used by human to communicate with a computer system. The input/output unit controls the flow of data to and from the processor. It also controls the external devices such as disc drives, monitor, printers, etc. connected to the computer system. For example, keyboard and mouse are input devices, while printers and monitors and LCD are output devices.

Bus and Bus Interconnection:

Bus is a communication pathway that is connecting two or more devices. The collection of paths i.e connecting the different (various) modules is called interconnection structure. A bus that connects CPU, Memory and Input / Output Systems is called System Bus. Bus interconnection is the communication channel that allows various components of the computer system to communicate with each other.

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