These computers come in different forms such as desktops, laptops, and personal digital assistants

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

These computers come in different forms such as desktops, laptops, and personal digital assistants

Google exec Amanda Rosenberg modeling Google Glass which fall under the small size computers

By Max Braun

The different types of computers can be grouped into six major categories according to size. Each category excels at specific functions.

  • Supercomputers
  • Mainframes
  • Mini-computers
  • Servers
  • Personal computers
  • Embedded systems

Generally, the size of the computer determines the processing abilities. Larger computers have higher processing speeds while smaller ones offer a better experience for personal computing.


These are arguably the most powerful in terms of speed and accuracy. They are types of computers used in solving complex mathematical computations. They are capable of executing trillions of instructions per second, which is calculated in floating point operations per second (FLOPS).

The typical personal computer used at home and the office is only capable of calculating millions of instructions per second (MIPS). Supercomputers can go even faster with the rate of petaFLOPS (or PFLOPS). This could bring up their processing numbers to the quadrillion.

Supercomputers were made popular in the 1960s by Seymore Cray. They soon became the choice for complex projects. They have evolved from the grid to cluster systems of massively parallel computing.

Cluster system computing means that machines use multiple processors in one system, rather than arrays of separate computers in a grid.

The operating systems that run in supercomputers vary depending on the manufacturer but are generally based on the Linux Kernel. A few popular ones include,

  • CNK OS used in Blue Gene from IBM
  • Cray Linux Environment used in Titan
  • Sunway Raise OS in Sunway TaihuLight

These computers are the largest in terms of size. They can occupy anything from a few feet to hundreds of feet. They also don’t come cheap as they can be priced between $200,000 to over $100 million.

These computers come in different forms such as desktops, laptops, and personal digital assistants

Tianhe-2 was the fastest supercomputer in 2013 - 2015

By O01326

The Top Supercomputers Since 2008

YearName of SupercomputerManufacturerSpeed in PFLOPS







Cray - USA



Tianhe - 1A

NUDT - China



K Computer

Fugitsu - Japan




Cray - USA



Tianhe - 2

NUDT - China



Tianhe - 2

NUDT - China



Tianhe - 2

NUDT - China



Sunway TaihuLight

NSC -China



Sunway TaihuLight

NSC -China


Uses of Supercomputers

Because of their superiority, supercomputers are not intended for your everyday tasks. They handle exhaustive scientific applications that require complex and real-time processing.

  • In the field of science, researchers use these machines to compute and model properties of biological compounds like protein and human blood. They are also used to interpret new diseases and strains and predict illness behavior and treatment.
  • The military uses supercomputers to test new aircraft, tanks, and a host of weaponry and camouflage. They also use them to understand the effects they will have on soldiers and wars. These machines are also used to help encrypt and decrypt sensitive data.
  • In entertainment, supercomputers are used to help make a flawless online gaming experience. Games like World of Warcraft demand intense processing. When thousands of gamers around the world are playing, supercomputers help stabilize the game performance.
  • Meteorologists use them to simulate weather behavior. They can also be used to predict earthquakes.
  • Scientists use them to simulate and test the effects of nuclear weapon detonation.
  • Scientists also use them to simulate the events of the Big Bang and other space-related projects.
  • Hollywood uses supercomputers to create realistic animations.
  • The famous supercomputers Deep Blue and Watson defeated chess Grandmaster Gary Kasparov and quiz expert Ken Jennings respectively.


Mainframe computers are large-sized computer types. They are equally powerful but fall short in terms of the computation ability in supercomputers. They are like big file servers, enabling multiple users from nearby and remote locations to access resources at the same time. Also known as big iron, these systems can handle massive amounts of data going in and out simultaneously. This makes them popular with businesses.

  • They are also resilient as they are capable of operating for over 10 years without failing.
  • Users access the mainframe using terminals or personal computers. This can happen within the same building or via a wide area network (WAN).
  • Most of these systems run the z/OS (operating system) on 64bit architecture.
These computers come in different forms such as desktops, laptops, and personal digital assistants

IBM System z9 mainframe is a large size computer type

By Ing. Richard Hilber

Uses of Mainframes

They are used in large organizations where thousands of clients have to access data simultaneously.

For example:

  • Performing ATM cash withdrawals and deposits. During the process, communication between the mainframe and remote computer will help accomplish the financial transactions at hand.
  • Business transactions that use credit cards or pre-paid cards.
  • Online electronic transactions.
  • Cloud storage.
  • Handling of patient records in major hospitals.
  • Making reservations and travel schedules for airline companies.
  • Manipulation and tallying of data for census and electoral purposes.

The price of mainframe computers, especially from IBM, starts at $75,000 and can go up to $1 million.

System z9, Fujitsu-ICL VME and Hitachi’s Z800 are examples of Mainframes.


Minicomputers are general-purpose devices without the monumental expenses associated with a larger system. Their processing power is below that of mainframe systems but above the capabilities of personal computers.

These computers come in different forms such as desktops, laptops, and personal digital assistants

Prototyp 1990, MicroVAX II Clone Minicomputer is a mid sized computer

By Procolotor

Also known as mid-range computers, these became popular in the late 1960s but have become almost extinct because of the popularity of personal computers. The latter can now perform most of the tasks reserved for minis.

The first minicomputer was unveiled in 1967 by Digital Equipment Corporation and was followed later by designs from IBM and other companies.

They became popular for control related functions as opposed to computing prowess. Over the years, their usage was limited to dedicated control assignments in mid-range organizations.

Minicomputers were intended for a number of activities listed below:

  • Switchboard control.
  • Dedicated applications for graphics and computer design.
  • Time-sharing, to allow multiple users to interact concurrently on a single system.
  • Control and monitoring of manufacturing activities.
  • Monitoring and control of laboratory equipment.

Texas Instrument TI-990, K-202 and MicroVAX II are examples of minicomputers.


These are types of computers used to provide resources, services, and functionality to client computers in a server-client network model. Resources provided are based on the functions of a particular server, which may fall under these categories:

  • File server
  • Database server
  • Print server
  • FTP servers
  • Application server
  • Webserver

Their sizes will depend on purpose and tasks in the network. Of course, bigger and more multitasking installations will require multiple systems and storage installations.

A common errant is that desktop systems can be used as servers. Far from it, true server systems are specialized computers with abilities far beyond what personal computers can deliver.

Servers are optimized to run 24 hours and are capable of hot-swapping of storage and other hardware without having to shut down the system.

These computers come in different forms such as desktops, laptops, and personal digital assistants

Hot swap disk drive bay in a server system

By Mixabest (Own work) [Public domain], via Wikimedia Commons

Microcomputers/Personal Computers

Microcomputers are the smallest, least expensive and the most used types of computers. They have a small memory, less processing power, are physically smaller, and permit fewer peripherals compared to super and mainframe computers. They are more commonly known as personal computers or simply PCs. The term was initially used to refer to IBM compatible computers.

They became popular in the 70s and 80s, at the dawn of the microprocessor chips. These chips meant that a machine used by one individual was now feasible.

The advent of PCs meant cheaper alternatives to more expensive and centralized systems. They were more affordable for office use and created cheaper networking environments. By the mid-1990s, they became the de facto computer of choice for offices and homes. The last 20 years have seen the proliferation of even smaller systems.

This signaled the start of the mobile age, which continued to go with the trend of smaller devices as the new century progressed. This ultimately gave birth to wearable computers and gadgets.

The operating system used in personal computers vary, but the common ones include:

  • Windows
  • Mac OS X
  • Linux
  • IOS
  • Android

Categories of personal computers include:

  • Desktop computers
  • Mobile computers
  • Wearable computers

Desktop Computers

Desktop computers are made up of separate components such as:

  • The system unit: a rectangular case that contains important parts like the motherboard, microprocessor, memory modules, disk drive, and optical drive
  • The monitor
  • A mouse
  • A keyboard
These computers come in different forms such as desktops, laptops, and personal digital assistants

A typical desktop computer fall under the small size computer that sit on desk

Single Unit Systems

Single unit computers, also known as all-in-one PCs, are a sub-type of desktop computers. They integrate the monitor and system unit within a single unit.

They also have connectivity to a mouse, keyboard, and other peripherals, usually through USB ports.

These computers come in different forms such as desktops, laptops, and personal digital assistants

All in one single unit computer

Nettop Systems

Nettops, which are sometimes called mini PCs, are small and cheap system units. They use less power and perform less processing.

Common features of Nettops include the Intel Atom microprocessor, 1-2 GB memory, and Wi-Fi connectivity.

Just like any other desktop, they attach to peripheral accessories via USB ports and the monitor via VGA or DVI ports.

These computers come in different forms such as desktops, laptops, and personal digital assistants

A nettop computer

Single-Board Computers

These are the smallest possible computers and mimic the shape and functionality of full-size desktop motherboards. They fit on miniature circuit boards, the size of an ATM card and spot numerous input/output ports for connectivity to external peripherals. Standouts are USB ports for a keyboard and mouse, HDMI output to monitors, Ethernet ports, and Bluetooth/wireless capability.

A single-board computer (SBC) is an integrated piece of hardware which is called so because it only spots one board, unlike the desktop computer which features additional circuitry like memory chips and processor.

It is also a low power, fan-less circuitry, low-cost system, and popular with hobbyists and developers.

An SBC can easily be confused with an embedded system because of its size but is not, because it permits general-purpose functionalities synonymous with microcomputers.

Raspberry Pi3, Arduino and BeagleBone Blue are popular examples of SBC.

These computers come in different forms such as desktops, laptops, and personal digital assistants

Raspberry Pi2 Single Board Computer (SPB)

By Les Pounder

Thin Clients

These are low-cost computer types that rely on server systems in order to provide computing services to attached monitors. They communicate to the server via the remote desktop protocol and are part of the networking implementation setup known as the client/server model.

While a thin client depends entirely on the availability of a server, a desktop based client (the typical desktop computer), sometimes called fat client, can operate independently of a server in case of transmission downtime.

A typical thin client features most input/output ports for connectivity to peripherals. Standouts are VGA or DVI ports to the monitor, PS/2 or USB ports for keyboard and mouse, and audio input/output ports.

These computers come in different forms such as desktops, laptops, and personal digital assistants

Ncomputing thin client

2. Mobile Computers (Laptops, Smartphones, Etc.)

Mobile devices have become the norm in recent years. Most users opt for laptops and tablets due to ease of use on the go, and battery power.

Particular features that make mobile systems a favorite include:

  • Extended battery use
  • Wi-Fi capabilities
  • Mobility

The most common types of mobile computers include:

  • Laptop computers
  • Tablets
  • Smartphones
  • Personal Digital Assistants (PDA)
These computers come in different forms such as desktops, laptops, and personal digital assistants

A 17 inch laptop and 10 inch netbook side by side.


Laptops are lightweight mobile PCs with a thin screen. They were initially called notebook computers because of their small size. They operate on batteries.

Unlike desktops, these systems combine the microprocessor, screen, and keyboard in a single case. The screen folds down onto the keyboard when not in use.


Ultrabooks are special laptops specifically designed to be thin and lightweight. They usually have longer-lasting batteries (5 hours minimum) and have strong hardware and processing power to run any software around.

Ultrabooks also ship with the faster SSD storage in place of the slower hard disk drives that are commonly used.


Chromebooks are low-end laptops that only run the web-based Chrome operating system. After the installation of Chrome OS, additional software can only be installed via the Chrome Web Store.

The OS allows you to achieve traditional PC functionality online. You can type documents, edit them, implement group discussions, have teleconferencing, and use basic online tools like search engines and e-mail.

These devices are increasingly targeted at users that spend most of their time online for social activities. Their hardware includes the Intel Atom microprocessor, Wi-Fi and wired network connectivity, solid-state disks (SSD), and an average of five hours of battery life. They usually do not have optical drives.

These computers come in different forms such as desktops, laptops, and personal digital assistants

By Alvin Trusty


Netbooks can be thought of as mini laptops. They are smaller in size, price, and processing power. Just like Chromebooks, they are primarily designed for web browsing, electronic communication, and cloud computing. They are catered to users who require less powerful client computers.

Their specs are similar to Chromebooks. The biggest difference is that they can run the lightweight Linux operating system.


A tablet is a mobile computer equipped with a touch screen or hybrid screen, which allows the user to operate it by use of a digital pen or fingertip.

Most tablets today are both multi-touch and multi-tasking, making it possible to manipulate them using multiple fingers and accomplishing multiple tasks simultaneously.

Tablets are handy, especially when normal notebooks and laptops are simply too bulky for the mobile user.

These computers come in different forms such as desktops, laptops, and personal digital assistants

An iPad is a mini tablet computer type


Back in 1996, a company called Palm Computing developed a gadget called Palm 1000. It was revolutionary in conception but did not actually build consumer excitement.

While the idea of a miniaturized computer was not new, the fact that someone had actually been able to make a device with an operating system that could work within its limitations was a huge leap forward. It was one of the biggest innovations in the tech industry.

The iPhone, released in 2007, was the first true smartphone. It became an instant hit with consumers worldwide. It started the smartphone industry that still persists today.

These computers come in different forms such as desktops, laptops, and personal digital assistants

An iPhone 6

Most smartphones today use an operating system such as IOS and Android. They often have the ability to add applications. This is in contrast to regular cellular phones which only support sandboxed applications like Java games. In terms of features, smartphones support full email capabilities as well as multiple functions to serve as a complete personal organizer.

Depending on the manufacturer, other functions might include additional interfaces such as miniature QWERTY keyboards, touch screens, built-in cameras, contact management, built-in navigation software, ability to read office documents in PDF and Word file formats, media software for playing music, browsing photos, and viewing video clips.

Personal Digital Assistants

Personal digital assistants (PDAs), also called handheld computers, pocket PCs, or palmtop computers, are battery-powered devices that are small enough to carry almost anywhere.

While weaker to larger systems, these are useful for scheduling appointments, storing addresses and phone numbers, and playing games. Some have more advanced capabilities, such as making telephone calls or accessing the Internet.

PDAs seem to have been overtaken by tablets and smartphones, almost rendering them obsolete.

Wearable Gadgets

Like the term suggests, wearable computers, or simply wearables, are miniature devices that are designed to be worn or attached onto your body.

Wearables are designed to function as smart devices similar to smartphones. They typically provide specific functions like health monitoring.

Whereas general purpose wearables offer a fuller computing experience that includes reading emails, the lesser systems will ship as embedded devices capable of minimal functions.

Examples of these devices include smartwatches, smart glasses, smart clothes, smart shoes, etc.


These became popular around 2013 when Samsung launched Gear, a wristwatch fitted with sensors to communicate directly with a smartphone.

Dubbed the smartphone and phablet companion, a smartwatch gives features like internet connectivity and text messaging among others.

It also provides communication between the user and other devices.

The leading tech companies in the world are all scrambling for opportunities in manufacturing smartwatches. Samsung launched Gear in 2013 and Apple has the Apple Watch. Other competitors include Sony, LG, and Google.

Head-Mounted Displays

Another wearable being developed is the heads up display unit (HUD) or head-mounted display unit (HMD).

This device is meant to be worn or attached to the head and uses a transparent glass display that interfaces with the human eye. It does not interfere with the user's sight.

Earlier HUDs were used for military purposes. They went from using a cathode ray tube to a liquid crystal display. The technology eventually embraced laser-based projection for images and motion pictures.

The current leader in this tech is Google Glass, which permits a number of functions like voice communication and reading tweets.

These computers come in different forms such as desktops, laptops, and personal digital assistants

By Tedeytan (Flickr)

Smart Ware

Smart shoes and smart clothes are intended for health-related functions like measuring heart rate and waveform measurement. These devices are intended to encourage the wearer to have an active lifestyle.

These computers come in different forms such as desktops, laptops, and personal digital assistants

Nike shoe showing the transmitter that communicates with the iPod

By Hamish2k

Smart shoes and smart clothes can also be used for competitive purposes, such as helping athletes keep track of their running distance and speed.

One of the first initiatives into developing these devices was the partnership between Apple and Nike. They created the Nike+iPod Sports Kit, a device for measuring distance and pace by the user. It worked by having the iPod communicate to the Nike show via voice prompts.

Embedded Systems

These are computer-based systems that are standalone electronic hardware designed to perform dedicated computing tasks. They are not general-purpose installations like the personal computer. Actually, they are computers which may not always seem to be computers!

They include a combination of the outer hardware, microprocessor chip, and software. The core of such systems is the microprocessor or microcontroller which executes the assigned task.

The embedded software, usually firmware, is but not always fixed onto volatile memory which may not always require post-installation configurations. In any case, the hardware does repetitive assignments.

The old cell phones used well before smartphones became a phenomenon, could easily fall under the category of embedded systems since their sole purpose was to make and receive calls. Smartphones today, however, have evolved into general-purpose mobile computers.

Firmware on these systems is written in the read-only memory (ROM) or flash memory chips. Despite the seemingly persistent firmware which is deemed unaltered, they can be re-programmed to suit evolving demands.

These computers come in different forms such as desktops, laptops, and personal digital assistants

Popular devices that may be categorized under embedded systems are listed below:

  • Set-top boxes
  • MP3 players
  • DVD players
  • Drones
  • Printers
  • Antilock braking systems
  • USB devices like internet dongles
  • Streaming players like Google Chromecast and Roku
  • Thermostats
  • Calculators
  • Toys
  • Digital cameras
  • ATM machines
  • Video game consoles
  • Routers and network peripherals
  • Computer add-on cards and peripherals
  • Digital watches

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


oseni hassan on March 16, 2020:

what is the different between ram and ROM

Tselot Seyoum on December 25, 2019:

good job but can computers be classified by other d/t categories

Engr Dynamic on December 24, 2019:

what is digital computer

Fatima on December 18, 2019:

education is a key of life no conditions is Permanent

kevn on November 28, 2019:

good work, am now comfortable with the system software thank you

Alfred Amuno (author) from Kampala on October 23, 2019:

Thanks Hazard

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Godswill on September 26, 2019:

Carolina Comment

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Bliss on January 11, 2019:

please what are the four type of computer and there size

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pure on December 10, 2017:

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fidelis Clinton on October 28, 2017:

thanks for the information

Alfred Amuno (author) from Kampala on October 20, 2017:

Thanks AbdulHameed for appreciating. Meanwhile, you can use Contact Author link at the top of this article for any correspondence.

abdulhameed on October 18, 2017:

nice job good pls can i have you contact or write it els were so that we will talk

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Emmah on May 10, 2017:

Thenks for that

Alfred Amuno (author) from Kampala on January 16, 2017:

Thanks for appreciating Ali

ali hassan on January 16, 2017:

thanks this article is very nice

Alfred Amuno (author) from Kampala on November 24, 2015:

Thanks Lizzie

lizzie on November 24, 2015:

Awesome text

Alfred Amuno (author) from Kampala on February 20, 2014:

Thanks Techpower.

Techpower on February 20, 2014:

Nicely explained -Followed

bfilipek on February 14, 2014:

@amuno future seems to be quite near :) It would be great to predict the future and create some new device or app for new kind of devices.

Alfred Amuno (author) from Kampala on February 14, 2014:

Thanks Thief for that.

Carlo Giovannetti from Puerto Rico on February 13, 2014:

Pretty good hub. Voted Up and Interesting.

Alfred Amuno (author) from Kampala on February 11, 2014:

True bfilipek, wearable devices will be the next wave in computing. In as far as flexible devices are concerned, I bet we wait to see how realistic and flexible they actually get.

bfilipek on February 11, 2014:

good hub! I think that wearable devices will become more and more popular. Also the world is waiting for "flexible displays" and will also bring new kinds of devices.