The computer system has the following three basic components:

Input Unit:

An input device is any hardware device that sends data to a computer, allowing you to interacts with and controls it. Data can be in the form of words, symbols, numbers, etc. The function of the input device is to direct commands and data into the computer. For example keyboard, mouse, scanners, digital cameras, joysticks, and microphones.

Central Processing Unit:

After receiving data and commands from the user, a computer system has to process the instructions provided using Central Processing Unit (CPU). 

It has three elements:

(a) Arithmetic and Logic Unit: An arithmetic logic unit (ALU) is a major component of the central processing unit of a computer system. It does all processes related to arithmetic and logic operations like add, subtract, multiply, etc.

(b) Control Unit: The control unit (CU) is a component of a computer’s central processing unit (CPU) that directs the operation of the processor. It tells the computer’s memory, arithmetic, and logic unit, and input and output devices how to respond to the instructions that have been sent to the processor.

(c) Memory Unit: A memory unit is the amount of data that can be stored in the storage unit. Once the data has been entered using input devices, the system stores the data in the memory unit.

Types of Memory:

Primary Memory & Secondary Memory.

• Primary Memory: It has 18 internal memory of the computer also known as main memory. It is of two types RAM and ROM.
• RAM (Random Access Memory): RAM stands for Random Access Memory also known as reading/write memory. Information stored in this memory is lost as the power supply to the computer is switched off; it is also called “Volatile Memory”.
• ROM(Read Only Memory): ROM stands for Read-Only Memory. ROM is a permanent type of memory. The contents are not lost as the power supply to the computer is switched off. ROM cannot be overwritten by the computer. It is also called “Non Volatile Memory”.
• Secondary Memory: It is the external memory of the computer which is used to store a large amount of data. The secondary storage devices are a Hard disk, Pen drive, CD, DVD, etc.

Output Unit:

An output device is any device used to send data from a computer to another device or user. Most computer data output that is ‘meant for humans is in the form of audio or video. Thus, most output devices used by humans are in these categories. Examples include monitors, projectors, speakers.