Components of a Computer System: Input and Output Units, CPU etc.

The compilation of these Application of Computers in Accounting Notes makes students exam preparation simpler and organised.

Components of a Computer System

Saying that computers have revolutionized our lives would be an understatement. These machines have completely changed the way we perform all daily tasks. In order to further maximize their potential, we must understand the core components of a computer system in detail – input unit, output unit, CPU.

Meaning of Computers

Computerized Accounting System

Computers, in simple words, are machines that perform a set of functions according to their users’ directions. Going by this definition, several electronic devices, from laptops to calculators, are computers.

A computer comprises some basic elements. These include hardware, software, programmes, data, and connectivity. No computer can function in the absence of these elements. Apart from these elements, a computer system comprises three basic components. These components are responsible for making computers actually function. Let’s take a look at them in detail.

Components of a Computer System

Every computer system has the following three basic components:

  1. Input unit
  2. Central processing unit
  3. Output unit

Components of a Computer System

While there are other components as well, these three are primarily responsible for making a computer function. They must work in complete synergy because that will ensure smooth overall functioning. Hence, we can even call them building blocks of a computer system.

Input Unit

These components help users enter data and commands into a computer system. Data can be in the form of numbers, words, actions, commands, etc. The main function of input devices is to direct commands and data into computers. Computers then use their CPU to process this data and produce output.

For example, a laptop’s keyboard is an input unit that enters numbers and characters. Similarly, even a mouse can be an input unit for entering directions and commands. Other examples include barcode readers, Magnetic Ink Character Readers (MICR), Optical Character Readers (OCR), etc.

Another example of input devices is touch screens. Users can simply touch these screens without using any other device to enter commands. From smartphones to ATM machines, these input devices are becoming very popular these days.

Central Processing Unit (CPU)

After receiving data and commands from users, a computer system now has to process it according to the instructions provided. Here, it has to rely on a component called the central processing unit. The CPU further uses these three elements:

a) Memory Unit
Once a user enters data using input devices, the computer system stores this data in its memory unit. This data will now remain here until other components of the CPU process it. The memory unit uses a set of pre-programmed instructions to further transmit this data to other parts of the CPU.

b) Arithmetic and Logic Unit
This part of the CPU performs arithmetic operations. It does basic mathematical calculations like addition, subtraction, division, multiplication, etc. Further, it can even perform logical functions like the comparison of data.

c) Control Unit
This unit is the backbone of computers. It is responsible for coordinating tasks between all components of a computer system. The control unit collects data from input units and sends it to processing units depending on its nature. Finally, it also further transmits processed data to output units for users.

Output Unit

The third and final component of a computer system is the output unit. After processing data, it is converted into a format which humans can understand. After conversion, the output units display this data to users. Examples of output devices include monitors, screens, printers, and speakers. Thus, output units basically reproduce the data formatted by the computer for users’ benefit.


Fill in the correct words in these sentences.

  1. There are _____ components in a computer system.
  2. Mathematical and logical functions are carried out by the _____
  3. _____ is the backbone of a computer system.
  4. Barcode scanners are examples of _____ unit.
  5. Storage of data happens in the ______ component.


  1. Three
  2. Arithmetic and Logic Unit
  3. Control Unit
  4. Input
  5. Central Processing Unit