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Functions of the Major Hardware Components of A Computer

The main function of a computer system is to process information.

Example of Information Processing

An example operation done using a computer is to create a flyer. The processing of the information required to create a flyer goes through a set of phases, each requiring it's own set of devices (computer hardware). For example, to design the flyer, the user must enter the text to be shown in the flier via a Keyboard. The user then enters the design of the flier via a mouse and keyboard. The computer then processes the information entered into instructions, executes these instructions and output the flyer to the user on his/her screen.

The image below shows the different phases the information went through.

1. Input

The first phase is the Input phase, where data is entered into the computer system through input devices. In the example, information was inputted via a mouse and keyboard - the keyboard was used to input the flyer text, and the mouse was used to input design for the flyer.

2. Processing

When the data is inputted into the computer system by the user, it is then processed by the Central Processing Unit (CPU). The CPU turns the inputted data into instructions it can understand. The CPU then processes these instructions and creates the required output. In the example of creating a flyer, the data would be the input from the user via keyboard and mouse. The CPU will process this data and create the flyer.

3. Storage (Temporary)

When the CPU reads in the data from the user, the CPU needs to store this data somewhere. This data is stored temporarily in main memory (discussed below) while the CPU is using it. The instructions that the data is transformed into is also stored in main memory. In our example, the data inputted by the user via the mouse and keyboard is stored in main memory while the CPU processes it. When the flyer is being created by the CPU, it is also stored temporarily in main memory.

4. Output

When the CPU is finished processing the data entered by the user, it can then output the result to the user. In our example, the outputted result will be the flyer - the CPU will output the flyer to the user by displaying it on the computer screen. The user can then choose to output the flyer to a page via the printer.

5. Storage (Permanent)

After the user gets the required output from the computer, he/she can then store this output permanently for future use. Data is stored permanently on secondary storage media such as a flash drive or on the computer's hard drive. In our flyer example, the user can store the designed flyer as a document that can be accessed later.

Major Hardware components

The major hardware components of a computer can be broadly categorized as:

  1. CPU (CU, ALU)
  2. Main Memory/Immediate Access storage (Primary Storage)
  3. Secondary Storage
  4. Input/Output Devices


The central processing unit (CPU) is the brain of a computer system. It carries out the instructions of a computer program, to perform the basic arithmetical, logical, and input/output operations of the system. The CPU is made up of the Control Unit(CU) and the Arithmetic and Logic Unit(ALU).
CU: The control unit is a part of the CPU that instructs other parts of the computer system to carry out program instructions.
ALU: The ALU is a a digital circuit that performs arithmetic and logical operations.

CPU ChipNewer CPU Chip

Main Memory

Main Memory is a form of Immediate Access Storage also known as primary storage, it is volatile memory directly accessible to the CPU and is used to store data actively operated on. The CPU continuously reads instructions stored there and executes them as required. Information stored in main memory is lost when the computer is powered off.

computer main memory chipdifferent memory chip sizes are used for different devices

Secondary Storage

Secondary storage differs from primary storage in that it is not directly accessible by the CPU. The computer usually uses its input/output channels to access secondary storage and transfers the desired data using an intermediate area in primary storage. Secondary storage does not lose the data when the device is powered off and it is non-volatile. Secondary Storage Devices Include the Hard Drive, Flash Drive, Memory Card. Secondary storage devices are discussed in depth at http://cleverlogic.net/book/types-secondary-storage-media

Compact Diskmagnetic tapeExternal Hard DriveUSB Flash Drive

Input Devices

An input device is any peripheral (piece of computer hardware equipment) used to provide data to the computer. Input Devices Include the Mouse, Keyboard, Touch Screen Monitor, Scanner, Track Pad, Microphone, Joystick, Web Camera.

ScannerMouseKeyboardGraphis Tablet

Output Devices

An output device is any piece of computer hardware equipment used to communicate the results of data processing carried out by the computer to the outside world. Output Devices include the Speaker, Printer, Monitor, Plotter.