Computers of the earlier years were of the size of a large room and were required to
consume huge amounts of electric power. However, with the advancing technology,
computers have shrunk to the size of a small watch. Depending on the processing
power and size of computers, they have been classified under various types. Let us
look at the classification of computers.
Different Types of Computers
Based on the operational principle of computers, they are categorized as
analog, digital and hybrid computers.
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Analog Computers
These are almost extinct today. These are different from a
digital computer because an analog computer can perform several mathematical
operations simultaneously. It uses continuous variables for mathematical operations
and utilizes mechanical or electrical energy. An analog computer operates in a quite different way. For a start, all operations in an analog computer are performed in parallel. Secondly, data are represented in an analog computer as voltages, a very compact but not necessarily robust form of storage (prone to noise corruption). A single capacitor (equivalent to the digital’s computer use of a transistor) in an analog computer can represent one entire continuous variable.
2. Digital Computers
They use digital circuits and are designed to operate on two states, namely bits 0 and 1. They are analogous to states ON and OFF. Data on these computers is represented as a series of 0s and 1s. Digital computers are suitable for complex computation and have higher processing speeds. They are programmable. Digital computers are either general purpose computers or special purpose ones. Special purpose computers, as their name suggests, are designed for specific types of data processing while general purpose computers are meant for general use.Early digital computers were electromechanical; electric switches drove mechanical relays to perform the calculation. These devices had a low operating speed and were eventually superseded by much faster all-electric computers, originally usingvacuum tubes. TheZ2, created by German engineerKonrad Zusein 1939, was one of the earliest examples of an electromechanical relay computer.
In 1941, Zuse followed his earlier machine up with the Z3, the world’s first working electromechanical programmable, fully automatic digital computer. The Z3 was built with 2000 relays, implementing a 22 bitword length that operated at a clock frequency of about 5–10 Hz. Program code was supplied on punched film while data could be stored in 64 words of memory or supplied from the keyboard. It was quite similar to modern machines in some respects, pioneering numerous advances such as floating point numbers. Rather than the harder-to-implement decimal system (used in Charles Babbage’s earlier design), using a binary system meant that Zuse’s machines were easier to build and potentially more reliable, given the technologies available at that time. The Z3 was Turing complete.
3. Hybrid Computers
These computers are a combination of both digital and analog
computers. In this type of computers, the digital segments perform process control by conversion of analog signals to digital ones.Hybrid computers can be used to obtain a very good but relatively imprecise ‘seed’ value, using an analog computer front-end, which is then fed into a digital computer iterative process to achieve the final desired degree of precision. With a three or four digit, highly accurate numerical seed, the total digital computation time to reach the desired precision is dramatically reduced, since many fewer iterations are required. One of the main technical problems to be overcome in hybrid computers is minimizing digital-computer noise in analog computing elements and grounding systems.
Classification of Computers
The following are the classification of the different types of computers based
on their sizes and functionalities: Mainframe Computers: Large organizations use mainframes for highly critical applications such as bulk data processing and ERP. Most of the mainframe computers have the capacities to host multiple operating systems and operate as a number of virtual machines and can substitute for several small servers. Mainframe computers (colloquially referred to as “big iron”) are computers used primarily by large organizations for critical applications; bulk data processing, such as census, industry and consumer statistics, enterprise resource planning; and transaction processing. They are larger and have more processing power than some other classes of computers: minicomputers, servers, workstations, and personal computers.
The term originally referred to the large cabinets called “main frames” that housed the central processing unit and main memory of early computers. Later, the term was used to distinguish high-end commercial machines from less powerful units. Most large-scale computer system architectures were established in the 1960s, but continue to evolve. Mainframe computers are often used as servers.
Minicomputers: In terms of size and processing capacity, minicomputers lie in
between mainframes and microcomputers. Minicomputers are also called mid-range systems or workstations. The term began to be popularly used in the 1960s to refer
to relatively smaller third generation computers.
Servers: They are computers designed to provide services to client machines in a
computer network. They have larger storage capacities and powerful processors.
Running on them are programs that serve client requests and allocate resources like
memory and time to client machines. Usually they are very large in size, as they have large processors and many hard drives. They are designed to be fail-safe and
resistant to crash.
Supercomputers: The highly calculation-intensive tasks can be effectively
performed by means of supercomputers. Quantum physics, mechanics, weather
forecasting, molecular theory are best studied by means of supercomputers. Their
ability of parallel processing and their well-designed memory hierarchy give the
supercomputers, large transaction processing powers.
Microcomputers: A computer with a microprocessor and its central processing unit
it is known as a microcomputer. They do not occupy space as much as mainframes
do. When supplemented with a keyboard and a mouse, microcomputers can be
called personal computers. A monitor, a keyboard and other similar input output
devices, computer memory in the form of RAM and a power supply unit come
packaged in a microcomputer. These computers can fit on desks or tables and prove
to be the best choice for single-user tasks.
Personal computers come in different forms such as desktops, laptops and
personal digital assistants. Let us look at each of these types of
computers.
Desktops: A desktop is intended to be used on a single location. The spare parts of
a desktop computer are readily available at relatively lower costs. Power
consumption is not as critical as that in laptops. Desktops are widely popular for daily
use in the workplace and households.
Laptops: Similar in operation to desktops, laptop computers are miniaturized and
optimized for mobile use. Laptops run on a single battery or an external adapter that
charges the computer batteries
Netbooks: They fall in the category of laptops, but are inexpensive and relatively
smaller in size. They had a smaller feature set and lesser capacities in comparison
to regular laptops, at the time they came into the market.
Personal Digital Assistants (PDAs): It is a handheld computer and popularly
known as a palmtop. It has a touch screen and a memory card for storage of data.
PDAs can also be used as portable audio players, web browsers and smart phones.
Most of them can access the Internet by means of Bluetooth or Wi-Fi
communication.
Tablet Computers: Tablets are mobile computers that are very handy to use. They
use the touch screen technology. Tablets come with an onscreen keyboard or use a
stylus or a digital pen. Apple’s iPod redefined the class of tablet computers.
Wearable Computers: A record-setting step in the evolution of computers was the
creation of wearable computers. These computers can be worn on the body and are
often used in the study of behavior modeling and human health. Military and health
professionals have incorporated wearable computers into their daily routine, as a
part of such studies. When the users’ hands and sensory organs are engaged in
other activities, wearable computers are of great help in tracking human actions.
Wearable computers do not have to be turned on and off and remain in operation
without user intervention.
REFERENCE:
1.http://blog.analogmachine.org/2012/03/15/analog-computers/ 2.https://en.m.wikipedia.org/wiki/Hybrid_computer 3.https://en.m.wikipedia.org/wiki/Computer#Digital_computers 4.https://www.computerhope.com/jargon/h/hybridco.htm 5.https://fi.m.wikipedia.org/wiki/VT100 6.https://computerhindinotes.com/mainframe-computer/mainframe-computer-2 7.https://www.istockphoto.com/my/photo/modern-server-room-interior-in-data-center-gm518406578-90020973 8.
Computer: A Series 
