As we interact with computers, we observe that they appear in different sizes, mode of operation and the purpose for which it meant. This has led to the classification of computers. They are classified based on the following:
- Type of Logic or Operating principles
- Size and Capability
- Purpose or Area of application
Based on the type of logic or operating principles, computers may be classified into one of the following:
- Digital computers
- Analogue computers
- Hybrid computers
Digital computers are those that use numbers in their operation. That is all quantities are expressed as discrete or numbers. They break all types of information into tiny units and use numbers to represent those pieces of information. Digital computer also work in very strict sequences of steps, processing each unit information individually, according to the highly organized instructions they must follow. They are very useful for arithmetic expressions and manipulation of data.
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| Digital computers; desktop (left) and laptop (right) |
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Analogue computers on the other hand represent data as variable points along a continuous spectrum of values. That is they make use physical relations in representing data and makes them somewhat flexible than the digital ones, but not necessarily more precise or reliable.
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| An analogue computer |
Hybrid computers are those systems that have features of digital computers and analogue computers. The digital part of a hybrid computer serves as the controller and provides logical operations while the analogue component usually serves as a solver of differential equations.
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| Wincatt Hybrid computer |
The size and capability of computers broadly group computers into the following:
- Supercomputers
- Mainframe computers
- Minicomputers and
- Microcomputers
Supercomputers are the most largest and powerful computers in the world. These systems can process large amounts of data and performing more than one trillion calculations per second. Some supercomputers can contain thousands of processors. Supercomputers are mainly used for large scale numerical problems in scientific and engineering disciplines as mapping human genome, weather forecast and modelling complex processes like nuclear fission.
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| Supercomputers housed in a large room |
Mainframe computers are those that have large storage capacity and high speed processing compared to minicomputers and microcomputers. They are used in larger organizations such as banks and insurance companies where many users need to access the same data. With regards to the use of mainframe computers, users are able to access its resources by means of a device called
terminal. There are two kinds of terminals namely;
dumb terminal and
intelligent terminal. A dumb terminal does not process or store data, it is simply an input/output (I/O) device that functions as window into a computer located somewhere else. An intelligent terminal can perform some processing functions but usually does not have any storage.
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| Mainframe computer |
Powerful mainframes can handle the processing needs of thousands of users at a given time. Sometimes a worker can use a standard personal computer to access the mainframe. They lack flexibility and can be used to handle specific set of tasks. An ATM transaction is a typical interaction between a user and a mainframe system.
Minicomputers derived their name from their size compared to other computers. Their capabilities lie between that of a mainframe and personal computer and are therefore referred to as
mid-range computers. Minicomputers can handle and process large data than personal computers and can serve the input and output needs of hundreds of users at a time. People can access a standard minicomputer by means of a terminal or standard PC.
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| A Minicomputer with a digital pen |
Microcomputers, also known as
personal computers (PC) are to be used by one person at a time. Although personal computers can be used by individuals, they can also be connected together to create networks. Computers in this category include:
- Desktops
- Workstations
- Notebook computers
- Tablet computers
- Handheld computers
- Smart phones
Desktop computers are the type of microcomputers designed to sit on a desk or table. They are found in schools, offices and homes. Desktops in recent years are more powerful than those a few years ago as they can be used for extremely amazing tasks. They can be used to communicate, produce videos, edit images and play sophisticated games. As its name implies, a desktop computer is too big to be carried around. The essential components of a desktop computer are housed in box-like structure called
system unit which consists of processing and storage components. The desktop computers come in two forms; the type that has the system unit horizontally oriented on the desk with the monitor on top and the most common type called tower pc where the system unit is placed vertically beside, under the desk or however desired.
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| Desktop computer; horizontal model |
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| Desktop computer; vertical or tower model |
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Workstations are specialized single-user computers that typically have more power than the standard desktop pc. They have greater average speed and are commonly used by scientist, engineers and animators to perform sophisticated tasks. Workstations often have high resolution and accelerated graphics features that make them suitable for architectural and engineering designs, modelling, video editing and animations.
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| Workstation computers |
Notebook computers are portable computers with an average weight between 3- 6kg and its mobility is enhanced by a briefcase or a bag. Because people mostly set these machines on their lap, they are often referred to as
laptops. Notebooks or laptops are costly than desktop pc’s. They can operate on either alternating current or special batteries. During its use, the lid is opened to reveal a monitor and a keyboard. When not in use, the device folds up for easy storage. Notebooks are fully functional microcomputers and because of its portability, they fall into the category of PCs called mobile computers.
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| Notebook computer also called laptop |
Tablet PCs: The tablet PC is the newest development in portable, full featured computers. Tablet PCs offer all the functionality of a notebook PC but they are small in size, lighter and can accept input from a special pen called
stylus or
digital pen- that is directly used to tap or write directly on the screen. Some tablet computers come with a fold-out keyboard making them appear more like a notebook PC. They can use special versions of programs that enable them to connect to networks and even external monitors.
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| Tablet computers |
Handheld PCs as the name implies are devices that are small enough to fit in the hand. A common type of handheld computer is the
Personal Data Assistant (PDA). A PDA is no larger than a pocket or appointment book and is often used for special tasks such as taking notes, displaying telephone numbers and addresses and keeping track of dates and agendas. Many PDAs have special software that allow their connectivity with larger computers to enable data exchange. Most handheld PCs come with a
pen that is used to touch and write on the screen and some also feature tiny in-built keyboards. Manu PDAs allow users to connect to the internet via wireless connection, with some others offering features like music players, cameras and global positioning systems (GPS).
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| Handheld PC with a touch pen |
Smart Phones: Some cellular phones double as miniature PCs because they offer advanced features not often seen in cellular phones and are therefore referred to as smart phones. Some of these great features include web and Email access, cameras, music players, text editors and sometimes remote control applications.
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| An Android smartphone |
Modern computer based on their area of application or purpose are grouped into:
- Special Purpose Computers
- General Purpose Computers
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special purpose computer is designed only to meet the requirements of a particular task or application. The instructions needed to perform a particular task are permanently stored into the internal memory, so that it can perform the given task on a single command. It therefore doesn’t possess unnecessary options and is less expensive. An example of a special purpose computer is a Nintendo video game or game console.
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| Specially purposed computers |
General Purpose computers are designed to perform multiple tasks with different programs at the same time. For instance, on single computer, a user can play video game and at the same time play music. In these computers, the instructions needed to perform a particular task are wired permanently into the internal memory. When one job is over, instructions for another job can be loaded into the internal memory for processing. This, a general purpose machine can be used to prepare pay-bills, manage inventories, print sales report and so on.
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| Computer for general purposes |
