Basic Components of Computer Systems

Computer refers to the electronic machine that is capable of following a set of instructions to produce the desired result as per the given instructions. It includes many elements like hardware, software, storage, etc. The components of a computer represent the primary elements necessary for basic functioning and to make the processing of data easy and convenient.

In this article, we are discussing the primary components of a computer along with the function of each. The working of each component is also explained with the help of a structural diagram. While the internal architectural design may change from one computer to another, the basic structure remains the same with the same working concept.

What are the main components of the computer?

There are many parts of a computer system that help to set up the whole system. When we work on it, it requires many internal and external devices to perform different tasks. However, when talking about computer components, a computer system is mainly made up of three primary components, namely:

Input Unit
Central Processing Unit
Output Unit

All these components participate in almost every task or activity performed on the computer system. While there are many other essential components, the above ones are the building blocks of any computer system, which ensure the smooth functioning of the computer. 

Let us understand the function of each component in detail with the following diagram:

Components of Computer

Input Unit

The input unit contains the devices required to input data into a computer system. Since computers do not react or operate on their own, the input unit is one of the main components of a computer. This unit establishes a link between the user and the computer so that the user can direct commands and data into the computer.

The devices used to input data into the computer are called input devices. These devices take data from the users and send it to the computer in a systematic manner for further processing. Like other electronic machines, the computer system also accepts only raw data (binary data). Input devices convert the data inputted by the user into binary form for the computer to understand. Data can be entered or given in the form of text, alphabets, numbers, symbols, images, etc.

The input unit transmits the data to the computer's primary memory (main memory), which is then processed by the computer's processor according to given instructions. The following are some of the commonly used input devices to perform the activities of an input unit:

Mouse: The mouse is one of the primary input devices that acts as a point-and-click device. It enables users to move the cursor and select specific objects on the computer's screen or monitor. The traditional mouse usually comes with three buttons, one on the left, one on the right, and one on the scrolling wheel. It can be connected to the computer both by wire and wireless.


Keyboard: The keyboard is another essential input device that consists of several keys. By pressing the keys, we can enter or input data like letters, numbers, signs, and other information on the computer. Like a mouse, it can also be wired and wireless.


Microphone: Microphone, short for mic, is an optional input device used on computers. When we need to insert audio into our presentation, do voice conferencing, recording, broadcasting, or giving voice commands to the computer, etc., we can connect a mic to the computer. 


Microphones come in a variety of shapes and sizes. It enables us to give voice input to the computer system. The mics are designed to read sounds from the surroundings and convert this sound (analog waves) into electrical signals. The signals are further converted into digital forms to be understood by the computer. 

Other examples of input devices include a webcam, scanner, touch screen, barcode reader, etc.

Central Processing Unit

The Central Processing Unit (CPU) is an essential electronic hardware component that controls and processes all functions in a computer system, including arithmetic and logical operations. All simple to complex calculations, tasks, or comparisons are performed by the CPU. It takes raw data from the primary memory, processes it or converts it into meaningful information desired by the users, and then sends the processed data back to the primary memory. 

The CPU is called the brain of the computer because it controls the operation of all the parts of the computer. Despite this, the computer's processor (CPU) also handles the operation of many other units within the computer system, such as the control unit, arithmetic logic unit, and memory unit. The Control Unit (CU) and the Arithmetic Logic Unit (ALU) are commonly called components of the CPU because they both together make up the CPU. 

Functioning of CPU

Control Unit

Control Unit (CU) is the main unit of the computer system as it controls all the operations and activities of the computer. It acts as a supervisor and controls the input/output, memory, and other devices in the computer. It establishes coordination between all the computer parts and determines the sequence of process execution for smooth functioning.

It retrieves instructions from the main memory, decodes the instructions, interprets the instructions, and produces meaningful information. In other words, the control unit collects the entered data using the input unit, forwards it for processing, and once it has done so, receives the output and presents it to the user using the output unit. It can be referred to as the center of all the processing activities that take place inside a computer device, making it the backbone of the computer to some extent.

Arithmetic Logic Unit

When mathematical or logical operations are to be performed/processed, the arithmetic and logic unit comes into play. It handles basic to complex operations of addition, subtraction, multiplication, and division. Moreover, it also processes actions such as data comparison and decision making. It means that this unit helps in performing logical operations like AND, OR, equal to, less than, and greater than, etc. 

Data is transmitted from memory to ALU when needed. After processing is complete, the information or result is either returned to memory to be stored permanently, or displayed through an output unit, or for further processing by the CPU, etc.

Memory Unit

The memory unit is an essential part of a computer system and it is required by the CPU to store data and instructions. It is used before processing, after processing as well as during the running of the process to store the current data. The memory unit is capable of accepting and transferring data/information to other units of the computer system with the help of the CPU when needed. 

There are mainly two types of memory inside the memory unit, namely primary memory and secondary memory.

Primary Memory: Primary memory typically stores input data and immediate calculation results. It is temporary memory and usually does not store large amounts of data. Also, it is a volatile memory and the data stored in this memory remains as long as it is connected to the power supply. Once disconnected from the power source or the computer is turned off, the data is lost or erased. RAM (Random Access Memory) is an example of primary memory in a computer. 


Primary memory uses a set of pre-programmed instructions to forward processed data (results or information) to other parts of the computer, such as output unit or secondary memory, etc.

Secondary Memory: Secondary memory or storage is used to permanently store the processed data for future use. Once the data is converted into meaningful information, it can be saved in secondary memory and the used memory can be released to some extent from the primary memory. 


Secondary memory is a non-volatile memory and preserves data even when the power supply is not connected. Hard disk drive (HDD) and Solid State Drive (SSD) are two popular secondary memory or storage devices used on computers.

Note: Primary memory has very fast read/write access, and thus is directly accessed by the computer's CPU. Secondary memory cannot be accessed directly and if data is read/written from/to the secondary memory, the data is first loaded into the primary memory and then accessed by the CPU for further processing. 

Output Unit

The output unit contains the devices needed to receive and view information from a computer system. The devices used to receive information or results from the computer are called output devices. This unit is an essential component of a computer because without it we cannot obtain or see information or desired results. Like the input unit, the output unit also establishes a link between the user and the computer.

As we discussed above, the results obtained after processing are stored in the primary memory before sending to other units. The output unit retrieves processed data from the computer's primary memory (main memory), which is converted into a human-understandable form before being displayed by the corresponding output device. The following are some of the commonly used output devices to perform the activities of an output unit:

Monitor: A monitor, often called a visual display unit, is one of the primary output devices used on computers these days. It is connected to a computer to digitally view the output (such as text, images, videos, etc.) on the screen. The output displayed on the computer's monitor is called soft copy output. The monitor is typically made of glass, circuitry, adjustment buttons, power supply, etc., all enclosed within a casing.


Printer: A printer is another essential output device used with computer systems these days. Unlike a monitor, a printer helps us to make a hard copy of the desired output such as a document, picture, or other information on paper. The printer takes electronic data from the computer and creates an exact copy of it in monochrome (in this context, black and white) or colors, depending on the type of printer. Impact and non-impact printers are the two primary types of printers.


Speakers: Speakers are used to receive audio/sound output from the computer system. They are optional and they can be connected to the computer only when we need to listen to something like music, movies, dialogues, etc. 
Modern computers (especially laptops) come with built-in speakers. However, we can also connect external speakers using the USB or audio jack port to get better quality sound output. 

Other examples of output devices include a projector, plotter, headphones, touchscreen, etc.


Although a computer system is a combination of several components, the primary components of a computer are the input unit, central processing unit, and output unit. All these units work to convert the raw data provided by the user into meaningful information desired by the user. During the entire conversion process, the data is stored in the primary memory and handled by the CPU as per the given instructions.

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