Explain Various Types of Computers?

Classification of Computers

Computers can be broadly classified into four categories based on their speed, amount of data that they can hold, and price (refer to figure). These categories are as follows : ·         Supercomputers ·         Mainframe computers ·         Minicomputers ·         Microcomputers

Supercomputers

Among the four categories, the supercomputer is the fastest, most powerful, and most expensive computer. Supercomputers were first developed in the 1980s to process large amounts of data and to solve complex scientific problems. Supercomputers use parallel processing technology and can perform more than one trillion calculations in a second. A single supercomputer can support thousands of users at the same time. Such computers are mainly used for weather forecasting, nuclear energy research, aircraft design, automotive design, online banking, controlling industrial units, etc.

Mainframe Computers

Mainframe computers are large–scale computers (but smaller than supercomputers). These are very expensive and need a very large clean room with air conditioning, thereby making them very costly to deploy. As with supercomputers, mainframes can also support multiple processors. Users can access mainframes by either using terminals or via PCs. There are basically two types of terminals that can be used with mainframe systems that are discussed as follows : Dumb Terminals Dumb terminals consist of only a monitor and a keyboard (or mouse). They do not have their own CPU and memory and use the mainframe system’s CPU and storage devices. Intelligent Terminals In contrast to dumb terminals, intelligent terminals have their own processor and thus can perform some processing operations. However, just like the dumb terminals, they do not have their own storage space. Usually, PCs can be used as intelligent terminals to facilitate data access and other services from the mainframe system. Mainframe computers are typically used as servers on the world wide web. They are also used in large organizations such as banks, airline companies and universities, where a large number of users frequently access data stored in their databases.

Minicomputers

As the name suggests, minicomputers are smaller, cheaper, and slower than mainframes. They are called minicomputers because they were the smallest computer of their times. Also known as midrange computers, the capabilities of minicomputers fall between mainframe and PCs. Minicomputers are widely used in business, education, hospitals, government organizations, etc. While some minicomputers can be used only by a single user, others are specifically designed to handle multiple users simultaneously. Usually, single–user minicomputers are used for performing complex design tasks. As with mainframes, minicomputers can also be used as servers in a networked environment, and hundreds of PCs can be connected to it.

Microcomputers

Microcomputers, commonly known as PCs, are very small and cheap. PCs can be classified into the following categories : Desktop PCs A desktop PC is the most popular model of PCs. The system unit of the desktop PC can be placed flat on a desk or table. It is widely used in homes and offices. Laptops Laptops are small microcomputers that can easily fit inside a briefcase. They are very handy and can easily be carried from one place to another. They may also be placed on the user’s lap (thus the name). Hence, laptops are very useful, especially when going on long journeys. Laptops operate on a special battery and do not always have to be plugged in like desktop computers. The memory and storage capacity of a laptops is almost equivalent to that of a desktop computer. As with desktop computers, laptops also have HDDs, floppy disk drivers, zip disk drives, etc. For input, laptops have a built–in keyboard and a trackball/touchpad, which is used as a pointing device. Workstations Workstations are single-user computers that have the same features as PCs, but their processing speed matches that of a minicomputer or mainframe computer. Workstation computers have advanced processors, more RAM and storage capacity than PCs. Therefore, they are more expensive and powerful than a normal desktop computer. Network Computers Network computers have less processing power, memory, and storage than a desktop computer. These are specially designed to be used as terminals in a networked environment. For example, some network computers are specifically designed to access data stored on a network (including the Internal and intranet). Some network computers do not have any storage space and merely rely on the network’s server for data storage and processing tasks. Network computers that are specifically designed to access only the Internet or intranet are often known as Internet PCs or Internet boxes. Handheld Computers The mid 1990s witnessed a range of small personal computing devices that are commonly known as handheld computers, Palmtop computers, or Mini–Notebook computers. These computers are called handheld computers because they can fit in one hand, while users can use the other hand to operate them. Handheld computers are very small in size, and hence they have small-sized screens and keyboards. Some examples of handheld computers are ·         Personal digital assistant (PDA) ·         Cellular telephones ·         H / PC Pro devices. Personal digit assistants (PDA) :  Today, the PDA (shown in figure) is among the most popular lightweight mobile devices that are used. A number of PDAs available in the market offer a collection of application software for word processing, spreadsheets, games, etc. PDAs are used to take notes, organize telephone numbers, and store addresses. The primary input device of a PDA is the stylus. A stylus enables the user to interact with the touchscreen to write text or drawn figures. It can be used to write notes. Some PDAs also support voice input. Cellular phones :  These days, cellular phones are web enabled telephones that have features of both analogue and digital devices. Such phones are also known as smart phones because, in addition to basic phone capabilities, they  also facilitate the users to access the Internet and send e-mails and faxes. H / PC Pro devices :  The H / PC Pro device see figure is based on a new development in handheld technology. The size and features of the H/PC Pro device is more than PDAs but less than that of typical notebook PCs. The H/PC Pro device includes a full-sized keyboard, RAM with very low storage capacity, and a slow-speed processor. However, these devices do not have a secondary storage disk.