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Classification of Computers by Size

Updated on January 16, 2017
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Alfred is a long time teacher and computer enthusiast who works with and troubleshoots a wide range of computing devices.

Google exec Amanda Rosenberg modeling Google Glass, a smple wearable computer
Google exec Amanda Rosenberg modeling Google Glass, a smple wearable computer | Source

When you classify computers by size, you basically are dividing them into different groups according to their sizes.These groups can be broken down into four major categories. They include:

  • Supercomputers
  • Mainframe computers
  • Mini-computers
  • Personal computers

The gigantic supercomputer with multiple microprocessors is known to perform extremely complex calculations, while the miniature wearable computer that is strung around the wrist or worn on the head is meant to perform only basic computing functions.

This means thus, huge computer size continue to mean higher processing speeds while reduced size means better experience in personal computing.

1. Supercomputers

Supercomputers are arguably the most powerful in terms of speed and accuracy and are useful in problems that require complex mathematical computations. They are capable of trillions of instructions per second, which is calculated in floating point operations per second (FLOPS). This is unlike personal computers which are capable of calculating only millions of instructions per second (MIPS).

When preceded with the prefix Peta (PFLOPS), supercomputer processing capacity is estimated at a whopping quadrillion floating point operations per second.

Supercomputers were made popular in the 1960s by Seymore Cray and soon became a choice for dedicated complex computational projects when decades later, they evolved from grid to cluster systems of massively parallel computing.

Cluster system computing meant that computers used multiple processors in one system, in contrast to arrays of separate computers in a grid.

Supercomputers are also large in terms of size and will occupy anything from a few feet to hundreds of feet. They also don’t come cheap as they sell for anything above $200,000 to $100s million.

Roadrunner supercomputer
Roadrunner supercomputer | Source

The top supercomputer every year from 2008

Name of Supercomputer
Speed 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

 Uses of Supercomputers

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

  • They are used to simulate various scientific experiments, to help understand how nature can cope in case the simulated incident occurs in real life.

For example:

  • Meteorologists use them to simulate weather behavior, including earthquakes in order to predict outcomes in advance.
  • Scientists use supercomputers to simulate and test the effects of nuclear weapon detonation.
  • Scientists also use them to simulate the events of the ‘big bang’, and various other space related projects.
  • Hollywood and other movie industries also use supercomputers to simulate and create realistic animations.

  • In the field of science, researchers use supercomputers 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 use supercomputers to test new aircraft, tanks and a host of weaponry and camouflage, and getting to understand the effects they will have on soldiers and wars. The military and intelligence agencies also use supercomputers to help encrypt and decrypt surveillance and other data.
  • In entertainment, supercomputers are used to help effect flawless gaming experience online. Games like World of War Craft demand intense graphics processing, and when thousands of gamers worldwide are at play, supercomputers helps streamline near perfect gaming experience.

The popular Deep Blue and Watson supercomputers also played chess and Jeopardy, and in so doing, defeated chess Master Gary Kasparov and quiz Master Ken Jennings respectively.

Chinese Supercomputer Leading in Speed

2. Mainframe Computers

Just like Supercomputers, Mainframe computers are equally large and powerful machines. They, however, fall short in terms of computation ability in comparison to the might of supercomputers. They are much like big file servers, enabling multiple users from nearby and remote locations to access mainframe resources at the same time.

Also known as big iron, one a mainframe computer will reliably support hundreds or thousands of users locally and internationally, to handle massive amounts of input-output of data, simultaneously.

This resilience makes them popular with the business fraternity because once powered up, they are capable of over 10 years of uptime without failing.

The users access the mainframe using terminals or personal computers. This can happen within the same building or via wide area network (WAN).

IBM System z9
IBM System z9 | Source

There are two types of terminals used to access mainframe computers:

  • Dumb Terminal

A dumb terminal, just like a thin client, does not normally have its own CPU and storage devices. This type of terminal uses the processing resources and storage within the mainframe computer. Typically, a dumb terminal consists of a monitor a keyboard and mouse.

  • Intelligent Terminal

An Intelligent terminal has its own processor and can perform some processing tasks. For example, personal computers in banking institutions are normally used as intelligent terminals. A personal computer as an intelligent terminal can access data and other services from a mainframe computer, and can also store and process data locally.

 Uses of Mainframe Computers

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

Examples include:

  • Transacting ATM cash withdrawals and deposits. While processing withdrawals and deposits via ATM machines, communication between the Mainframe and remote computer will help accomplish the financial transactions at hand.
  • Business transactions that use credit card or pre-paid cards in a retail store.
  • Online electronic transactions i.e e-banking.
  • Cloud storage.
  • Handling of patient records in major hospitals.
  • Transacting reservations and travel schedules for airline companies.
  • Manipulation and tallying of input-output data for census and electoral purposes.
  • Telecom companies

Price of modern day mainframe computers, especially from IBM, start at $75,000 to around $1 million.

3. Minicomputers

Minicomputers are general purpose computers without the monumental expenses associated with a larger system like the mainframe computer and minimal computing power of the personal computer. In brief, the processing capabilities of minicomputers lie between the mainframe and personal computers.

Prototyp 1990, MicroVAX II Clone Minicomputer
Prototyp 1990, MicroVAX II Clone Minicomputer | Source

Also known as mid-range computers, the minicomputer became popular starting in late 1960s and reduced in usage by 1990s. The first minicomputer was unveiled in 1967 by Digital Equipment Corporation and was followed later by designs from IBM and other companies.

Minicomputers became popular for control related functions as opposed to computing prowess of supercomputers and immense input-output data manipulation that is associated with mainframe computers.

Over the years, usage of minicomputers was limited to dedicated control assignments in mid-range organizations.

It is important to note that original and later usage of minicomputers was blurred between server applicability and heavy design usability associated with workstations.

Minicomputers are intended for a number of activities that include,

  • Switchboard control as in telephone switching
  • Dedicated applications like graphics and computer design assignment
  • Time sharing i.e. server and other assignments in network environment
  • Control and monitoring of manufacturing activities
  • Monitoring and control of laboratory equipment

4. Microcomputers: Personal Computers

Microcomputers are the smallest and least expensive general purpose computers. They have small memory, less processing power, are physically smaller and permit fewer peripherals to be attached. Microcomputers are commonly known as personal computers or simply PC, a term that was initially used to mean IBM compatible computers, a name that is now common place.

They became popular in in 1970s - 1980s, at the dawn of the microprocessor chips. The birth of microprocessors meant that a computer usable by one individual was now feasible.

The advent of personal computers meant cheaper computer alternatives to more expensive and centralized minicomputers. This made PCs more affordable for office and cheaper networking environments. By mid-1990s, they became the de facto computer of choice for office and home.

To complement traditional PCs, innovations during the last and first decades of the 20th and 21st Century saw the proliferation of even smaller computers.

This signaled a mobile age which continued to go miniature as the new century progressed, ultimately giving birth to wearable computers and gadgets.

Categories of personal computers in this chapter include:

  • Desktop computers
  • Mobile computers
  • Wearable computers

A desktop computer, an example of a personal computer
A desktop computer, an example of a personal computer

(a) Desktop Computers

Desktop computers are designed for use on top of desks or on tables. They are typically larger and more powerful than mobile computers. Desktop computers are made up of separate components namely:

  • The system unit; a rectangular case that contains important parts like motherboard, microprocessor, memory modules, disk drive, optical drive etc.
  • The monitor
  • A mouse
  • A keyboard

 Single Unit Computers

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

Just like the basic desktop computer, they also have connectivity to mice, keyboard and other peripherals, usually attached to USB ports.

Nettop Computers

Nettop, which are sometimes called mini PCs, are small factor system units. They are inexpensive miniature computers that use less power and lower end processing.

Common features of Nettop computers include Intel Atom microprocessor, 1 – 2 GB memory, and wi-fi connectivity.

Just like any other desktop computer, they attach to peripheral accessories via USB ports.

A nettop computer
A nettop computer

(b) Mobile Computers

Mobile computers have in recent years become the norm. Most users have opted for laptops and tablets owing to the ease of using them on the go and not having to rely on bigger computers back at home.Whereas desktop computers limit the user to local disk storage, mobile computers take advantage of online cloud storage.

Particular features that make mobile computers a favorite include:

  • Extended battery use
  • Wi-fi capabilities
  • Mobility

The most common types of mobile computers include:

  • Laptop (Notebook) computers
  • Tablets
  • Smartphones
  • Personal Digital Assistants (PDA)

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

 Notebooks: Laptop Computers

Laptop computers are lightweight mobile PCs with a thin screen. They were initially called notebook computers because of their small size compared to the size of paper notebooks. Laptops operate on batteries making them appropriate to carry around.

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

 Ultrabooks

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 used in contemporary laptops.

 Chromebooks

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

Chrome OS allows you to achieve traditional PC functionality online. You can type documents, edit them, implement group discussions, via audio and video-teleconferencing, and accomplish basic online activities like search and mail.

Chromebooks are increasingly targeted for users that spend most of their time online, for social and web-based activities. Chromebook specs run at a minimum which include Intel Atom microprocessor, wi-fi and wired network connectivity, solid state disks (SSD) and an average of five-hour battery life. They usually do not have optical drives.


 Netbook Computers - Mini Laptops

Netbook computers are sub-laptop, or mini laptop computers, defined by small size, price, microprocessor power, and operating system. Just like Chromebooks, they are primarily designed for web browsing, electronic communication and cloud computing users who require less powerful client computers. Specs in Netbooks mimic those in Chromebooks.

Unlike Chromebooks though, Netbook computers run lightweight Linux™ operating systems and Windows 7 Starter and do not have optical drives.

Tablet Computers

A tablet PC 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, instead of the traditional keyboard and mouse.

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

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

An iPad mini tablet
An iPad mini tablet

 Smartphones

Back in 1996 a company called PalmComputing, developed a new piece of electronic gadget called Palm 1000. It was revolutionary in conception but did not actually attract consumer excitement.

While the idea of a miniaturized computer was not new, the fact that someone had actually been able to make one and design an operating system that could work within its limitations, was a huge leap forward. It is one of those revolutionary events that hit tech industries every few years.

The iPhone which was released in 2007 was the first true and revolutionary smartphone, becoming an instant hit with consumers worldwide. It started an amazing smartphone warfare that still persists.

An iPhone smartphone
An iPhone smartphone

A smartphone allows the user to make phone and video calls, listen to mp3 and watch video files, and is capable of data network.

Most smartphones today use an operating system i.e IOS and Android, often with the ability to add applications in contrast to regular cellular phones which only support sandboxed applications like Java games. In terms of features, smartphones too support full featured email capabilities with the functionality of a complete personal organizer.

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

 Personal Digital Assistants (PDA)

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

Although not as powerful as desktops or laptops, handhelds 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.

Instead of keyboards, handhelds have touch screens that one uses with the fingertip or a stylus (a pen-shaped pointing tool).

However, PDAs seem to have been overtaken by tablet computers and smartphones, almost rendering them obsolete.

(c) Wearable Computers

Like the term suggests, wearable technology computers or simply wearables, are miniature devices which are designed to be worn or attached onto human body parts. They are meant to be placed in close proximity to user skin, hand, eye and mouth.

Wearables are designed to function as smart devices similar to smartphones (almost), or provide limited assignments like health monitoring.

Whereas general purpose computer wearables offer near computing experience that include reading emails, tweets, social posts, audio-visual capabilities, voice communication and physical fitness related functions, the lesser wearables will ship as special purpose embedded devices capable of bare minimum of functions.

Examples of wearable computers include smartwatches, smartglasses, smartclothes, smartshoes etc.

 Smartwatches

Wearable computers became popular starting in 2013 when Samsung launched Gear, a wrist based watch, which is fitted with sensors to communicate directly with a smartphone.

Dubbed the smartphone and phablet companion, a smart watch gives features like internet connectivity i.e. reading email, watching video, reading weather news, text messaging among others.

It also provides direct and immediate 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 is rumored to be developed its own smartwatch. Other competitors include Sony, LG and Google.

 Head Mounted Display

Apart from smartwatches, another wearable being developed is the heads up display unit (HUD) or head mounted display unit (HMD).

A heads-up display device is meant to be worn or attached to the head and uses a transparent glass media to effect communication using the human eye(s), and does not interfere with user sight.

Earlier HUDs were used to facilitate in military navigation, before transforming to cathode ray tube, and later to liquid crystal display as used by pilots. The technology eventually embraced laser-based projection for images and motion pictures.

The present flag bearer in heads up display is Google Glass which permits a number of functions like voice communication, reading tweets etc.


Among other specs, the initial Google Glass features 5 mega pixel photos, 720p video camera, wifi, Bluetooth and 12 gigabyte storage.

 Smartware

Smartshoes and smartclothes are intended for health-related functions like foot and heart rate and waveform measurement, and as a health monitoring device to help encourage the wearer to have an active lifestyle for health maintenance.

Nike shoe showing the transmitter that communicates with the iPod
Nike shoe showing the transmitter that communicates with the iPod | Source

Smartshoes and Smartclothes can also be used for competitive purposes, helping athletes measure and speed up to foot rates of better athletes. This helps them compete favorably.

One of the first initiatives into health and wearable interaction was the partnership between Apple and Nike, in what is popularly known as Nike+iPod Sports Kit, a device for measuring distance and pace walked or run by the user.

The Nike – Apple partnership makes use of a Nike training shoe and Apple’s iPod. Accompanied by voice prompts and tips from the iPod, in communication with the shoes, the user gets to know how best to approach fitness and attain healthy living.

5. Embedded Systems

Embedded devices are dedicated with specialized computer chips which are built into standalone electronic systems, to enable special computing tasks. Embedded computers are pre-programmed and can be re-programmed to suit changing features, demand and time.

Firmware on these systems are written on permanent read-only memory (ROM) chips which require on-site and remote flashing to re-program them.

For example, a special chip is embedded within a set top box to enable it provide TV services.

A digital decoder - set top box
A digital decoder - set top box

Embedded computers are used in sample electronic devices and gadgets listed below:

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


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    • profile image

      bfilipek 3 years ago

      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.

    • amuno profile image

      Alfred Amuno 3 years ago from Kampala

      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.

    • Thief12 profile image

      Thief12 3 years ago from Puerto Rico

      Pretty good hub. Voted Up and Interesting.

    • amuno profile image

      Alfred Amuno 3 years ago from Kampala

      Thanks Thief for that.

    • profile image

      bfilipek 3 years ago

      @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.

    • Techpower profile image

      Techpower 3 years ago

      Nicely explained -Followed

    • amuno profile image

      Alfred Amuno 3 years ago from Kampala

      Thanks Techpower.

    • profile image

      lizzie 16 months ago

      Awesome text

    • amuno profile image

      Alfred Amuno 16 months ago from Kampala

      Thanks Lizzie

    • profile image

      ali hassan 2 months ago

      thanks this article is very nice

    • amuno profile image

      Alfred Amuno 2 months ago from Kampala

      Thanks for appreciating Ali

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