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The Four Categories of Computer Hardware

Alfred is a long-time teacher and computer enthusiast who works with and troubleshoots a wide range of computing devices.

An illustration of desktop computer set  comprising all the categories of computer hardware.

An illustration of desktop computer set comprising all the categories of computer hardware.

Computer hardware refers to the physical devices that make up a computer. Examples include the keyboard, monitor and disk drive.

Hardware devices can be classified into four distinct categories:

  • Input devices: For raw data input.
  • Processing devices: To process raw data instructions into information.
  • Output devices: To disseminate data and information.
  • Storage devices: For data and information retention.

1. Input Devices

Components which are used to input raw data are categorized under input devices. They aid in feeding data such as text, images, and audiovisual recordings. They even aid in file transfers between computers.

The keyboard is probably the most commonly used input device. Below are just some other types of input devices.

A microphone is an example of a sound input device.

A microphone is an example of a sound input device.

Input TypeExamples

Pointing Device

Mouse, touchpad, touchscreen, multi-touch screen, pen input, motion sensor, graphics tablet, interactive smartboard, and fingerprint scanner.

Game Controller

Joystick, gamepad, and steering wheel.

Audio Input Device

Microphone and midi keyboard.

Bluetooth Peripheral

Keyboard, mouse, headset, gamepad, printer.

Visual and Imaging Device

Webcam, digital camera, digital camcorder, TV capture card, biometric scanner, and barcode reader.

Network Device

Ethernet hardware and Bluetooth/wireless hardware.

2. Processing Devices

Processing is the core function of a computer. It is the stage where raw data is transformed into information. Once data has been processed, it can be used for useful purposes.

An AMD microprocessor is an example of a processing device.

An AMD microprocessor is an example of a processing device.

Components that manipulate data into information are categorized under processing.

The microprocessor is the major device in this category. It works closely with primary memory during its operations. Data is stored temporarily in processor cache and primary memory during the processing period.

The microprocessor is subdivided into three important units, which work together in order to accomplish its function. The units are:

  • The control unit: It manages and supervises the operations of the processor and other components that are crucial in data manipulation.
  • Arithmetic and logic unit: The ALU is responsible for all arithmetic and logic operations like addition, multiplication, subtraction, division, and comparison logic operations.
  • Register and cache: These are storage locations inside the processor that respond to the instructions of the control unit by moving relevant data around during processing.

3. Output Devices

Hardware components that disseminate and display both data and information are classified under the output category.

Output is the culmination of a cycle which starts with the input of raw data and processing.

These components are sub-categorized under softcopy and hardcopy output.

Softcopy output includes the intangible experience. The user derives visual satisfaction by reading a message through display components or listens to audio files through speakers.

On the other hand, hardcopy output devices are tangible, like printouts of paper and 3D models.

The CRT monitor is an output device.

The CRT monitor is an output device.

Popular Softcopy Devices

Visual display devices include:

  • Monitor
  • Projection display
  • Interactive (electronic) smartboard
  • Touchscreen

Sound devices include:

  • Speakers
  • Headphones and earphones

Network input/output includes:

  • Ethernet cables
  • Wireless and Bluetooth transmissions

USB input/output includes:

  • Flash drives
  • External drives
  • Optical drives

Popular Hardcopy Devices

Impact printers include:

  • Dot matrix printer
  • 3D printer

Non-impact printers include:

  • Inkjet printer
  • Laserjet printer
  • Thermal printer
A 3D printer

A 3D printer

4. Memory/Storage Devices

Components that retain/store data are classified under memory/storage devices.

Storage is sub-divided under primary and secondary memory and is either volatile or nonvolatile.

Primary memory usually refers to random-access memory (RAM) but can also refer to all memory that works in tandem with the processor. RAM is volatile, meaning that it retains data only when the computer is powered up.

The central processing unit (CPU) or accelerated processing unit (APU) reads instructions stored in this memory and executes them as required.

Computer memory devices.

Computer memory devices.

Secondary memory is labeled as such because data stored within secondary storage media (usually disk drives) do not communicate directly with the microprocessor. Any data stored in such media is first transferred to a RAM device for processing to take place.

This type of memory is also non-volatile since it permits long time storage as opposed to volatile memory.

To give some examples of these devices, primary memory includes:

  • DRAM
  • SRAM
  • ROM

Secondary memory is subdivided into two categories:

  • Internal devices are designed to be placed inside the computer at all times. Examples include hard disk and solid state disk drives.
  • External devices are plug and play media used to transfer files between computers. Examples include optical disks, flash disks, and external disk drives.

This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.

© 2014 Alfred Amuno


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