Types of Computer

Computers can be classified, or typed, in many ways. We can categorize computer in two ways: on the basis of data handling capabilities and size.

On the basis of data handling capabilities, the computer is of three types:

• Analogue Computer
• Digital Computer
• Hybrid Computer

Analog computer, any of a class of devices in which continuously variable physical quantities such as electrical potential, fluid pressure, or mechanical motion are represented in a way analogous to the corresponding quantities in the problem to be solved. The analog system is set up according to initial conditions and then allowed to change freely. Answers to the problem are obtained by measuring the variables in the analog model.

The earliest analog computers were special-purpose machines, as for example the tide predictor developed in 1873 by William Thomson (later known as Lord Kelvin). Along the same lines, A.A. Michelson and S.W. Stratton built in 1898 a harmonic analyzer (q.v.) having 80 components. Each of these was capable of generating a sinusoidal motion, which could be multiplied by constant factors by adjustment of a fulcrum on levers. The components were added by means of springs to produce a resultant. Another milestone in the development of the modern analog computer was the invention of the so-called differential analyzer in the early 1930s by Vannevar Bush, an American electrical engineer, and his colleagues. This machine, which used mechanical integrators (gears of variable speed) to solve differential equations, was the first practical and reliable device of its kind.

Most present-day electronic analog computers operate by manipulating potential differences (voltages). Their basic component is an operational amplifier, a device whose output current is proportional to its input potential difference. By causing this output current to flow through appropriate components, further potential differences are obtained, and a wide variety of mathematical operations, including inversion, summation, differentiation, and integration, can be carried out on them. A typical electronic analog computer consists of numerous types of amplifiers, which can be connected so as to build up a mathematical expression, sometimes of great complexity and with a multitude of variables.

Analog computers are especially well suited to simulating dynamic systems; such simulations may be conducted in real time or at greatly accelerated rates, thereby allowing experimentation by repeated runs with altered variables. They have been widely used in simulations of aircraft, nuclear-power plants, and industrial chemical processes. Other major uses include analysis of hydraulic networks (e.g., flow of liquids through a sewer system) and electronics networks (e.g., performance of long-distance circuits).

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Digital Computer :
Digital computers are the computer systems/machines which uses the binary number system, which has two digits: 0 and 1 and performs many computational tasks. It processes the data represented in discrete and the main three components of digital computers are input, processing and output. The first digital computer was designed for numerical computations in the late 1940s. Digital computers give results with more accuracy as it is not dependent upon physical quantities for processing a task.

We have four different computer types classified according to their performance, power, and size. A computer is an electronic device that accepts data, processes it, stores, and then produces an output.

There are different computer types available depending on the number of users they can support at any one time, their size, and power. Depending upon the internal structure and subsequent features and applicability, computer system is categorized as follows

Supercomputers 

Supercomputers are very expensive, very fast, and the most powerful computers we have in the world.

Supercomputers are optimized to execute a few numbers of programs. This makes it possible for them to execute these few programs at a very high speed. Due to their inhibiting cost, they are used in high-end places like in scientific research centers. The supercomputer consists of thousands of processors making it clock very high speeds measured by petaflops.

These computer types are also very large in size due to the numerous parts and components involved in their design.

This category of computer is the fastest and also very expensive. A typical supercomputer can solve up to ten trillion individual calculations per second.

The world’s most powerful supercomputer today is Summit, built by IBM for the U.S. Department of Energy’s Oak Ridge National Laboratory in Tennessee.

PARAM-Siddhi is the second Indian supercomputer to be entered in the top 100 on the Top500 list.

Pratyush, a supercomputer used for weather forecasting at the Indian Institute of Tropical Meteorology, ranked 78th on the November edition of the list.

Mainframe computers

These are large and expensive computer types capable of supporting hundreds, or even thousands, of users simultaneously. Thus, they are mostly used by governments and large organizations for bulk data processing, critical applications, transaction processing, census, industry and consumer statistics among others. They are ranked below supercomputers.

mainframes computers are the type of computers that have high-performance can be used for intensive processing of operations that cannot be done by normal computers. The mainframe computers are mainly used in the banking sector, corporate sector, and government agencies as there is always a requirement of the secured system so that transactions can be done in a secure manner, and data can be kept safe from the external world. There is a different type of mainframes computers that can be distinguished on the basis of operating systems, data code set, and manufactures. Some of the mainframe computers are ENIAC, UNIVAC, ASCC.

Some of the advantages and disadvantages of mainframe computers.

Advantages

The mainframe computers are widely used in different sectors as they have several advantages. Some of them are mentioned below:

• High Computing Power: There is an inbuilt capability in mainframe computer to process massive chunks of data and can also support the complicated applications to run with high computing speed. The complex applications can be developed and run in mainframes computer.
• Scalability: The mainframe computers have the compatibility with big power type processors and other ultra power processors can be added in the mainframe computer to increase the computing speed. The mainframe computers also support increasing the size of the storage device so that huge chunks of data can be processed easily.
• Virtualization System: The mainframe computers use the concept of virtualization in which the whole system is divided into tiny logical segments so that memory limitation issues can be resolved and computing performance can be increased for a mainframe computer.
• Reliability: The mainframe computers are very reliable as the bugs and threats can be easily identified in this type of computer and can be self recover without using any embedded resources. The mainframe computers are so reliable that they can run for 40-50 years without the need for any kind of maintenance.
• Self-Serviceability: As the mainframe computers are reliable in nature it has the capability to self identify the threats and bugs and then self recover from that bugs. The mainframe computer does not allow to degrade the performance and recover from the bugs in a very short time span.
• Protection: The mainframe computers are used by the large-scale organization as there is a requirement of protecting the confidential data and information from the external world. The mainframe computer uses the advanced authentication system that provides extra protection to the large-scale organization and they can easily use the mainframe computer.
• Flexible-customization: The mainframe computer design is flexible and can be modified as per the user requirement. In the mainframe computer, there is functionality that at a time multiple operating systems can be installed in the system. And as the performance measure is very good for the mainframe computer the usability of system increases in every sector like banking sectors, corporate sectors, and government agencies. At a time multiple applications can be run in the system without affecting the performance of the system.

Disadvantages

As there are several disadvantages of mainframe computers but there are still some flaws present in mainframe computers. Some of them are mentioned below:

• As there are very advanced features in mainframe computers it directly increases the cost of the system and cannot be afforded by a normal user. The large-scale organization can only afford the mainframe computers. The features offered by mainframe computers are also not relevant to the normal user as the user requirement is very low compared to features offered by mainframe computers.
• The environment needed to mainframe computers is different from normal computers. As temperature should be very low where the mainframe computers are placed. The space required for mainframe computers is also very large compared to normal computer systems.
• Need of professional staff to handle the mainframe operations and handle the bugs and errors if the system reports.
• If any component goes down then the whole system goes down that is considered as a major setback for mainframe computers.
• The resource consumption of mainframe computers is very large compared to normal computer systems. As the mainframe computers offer advanced features it requires too many resources thus ultimately increase the cost of the system.
• As there are more than one operating system can be installed in mainframe computers thus it increases the complexity to read instructions and increase complexity for the user to use the system.

Minicomputers : 

Computer that is smaller, less expensive, and less powerful than a mainframe or supercomputer, but more expensive and more powerful than a personal computer. Minicomputers are used for scientific and engineering computations, business-transaction processing, file handling, and database management, and are often now referred to as small or midsize servers. In terms of size and power, minicomputers are ranked below mainframes. A minicomputer is a multiprocessing system capable of supporting from 4 to about 200 users simultaneously.

The use of the term Minicomputer has diminished and they have merged with servers. A minicomputer may also be called a mid-range computer. 

Minicomputers emerged in the mid-1960s and were first developed by IBM Corporation. They were primarily designed for business applications and services that require the performance and efficiency of mainframe computers. Minicomputers are generally used as mid-range servers, where they can operate mid-sized software applications and support numerous users simultaneously.

Minicomputers may contain one or more processors, support multiprocessing and tasking, and are generally resilient to high workloads. Although they are smaller than mainframe or supercomputers, minicomputers are more powerful than personal computers and workstations. 

Microcomputers 

A personal computer is a computer designed to be used by one user at a time. The term microcomputer relates to the microprocessor which is used with a personal computer for the purpose of processing data and instruction codes. These are the most common computer types since they are not very expensive.

Microcomputer, an electronic device with a microprocessor as its central processing unit (CPU). Microcomputer was formerly a commonly used term for personal computers, particularly any of a class of small digital computers whose CPU is contained on a single integrated semiconductor chip. Thus, a microcomputer uses a single microprocessor for its CPU, which performs all logic and arithmetic operations. The system also contains a number of associated semiconductor chips that serve as the main memory for storing program instructions and data and as interfaces for exchanging data of this sort with peripheral equipment—namely, input/output devices (e.g., keyboard, video display, and printer) and auxiliary storage units. Smaller microcomputers first marketed in the 1970s contain a single chip on which all CPU, memory, and interface circuits are integrated.

As large-scale integration and then very-large-scale integration have progressively increased the number of transistors that can be placed on one semiconductor chip, so the processing capacity of microcomputers using such single chips has grown commensurately. During the 1980s microcomputers came to be used widely in other applications besides electronic game systems and other relatively simple computer-based recreations. Increasingly powerful microcomputers began to be used in personal computer systems and workstations, for instance. High-performance microcomputer systems are used widely in business, in engineering, in “smart” or intelligent machines employed in the factory and office, and in military electronics systems.

In the early 1990s, small computers that fit in a pocket yet provide the power of a desktop personal computer were introduced. These pocket, or palm-sized, computers, commonly known as personal digital assistants (PDAs), are distinguished by their high portability, enhanced performance, and low cost. Similarly, microprocessors began finding their way into cellular telephones and portable MP3 music players.

As personal computers started including multiple processors in the 2000s, microcomputer began to be relegated to descriptions of small “embedded” computers found in various electronic devices.

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Difference between Analog Computer and Digital Computer :

S.No.	ANALOG COMPUTER	DIGITAL COMPUTER
01.	Analog computers works with continuous values or these types of systems process continuous data.	Digital computers works with discrete values or these types of systems process discrete data.
02.	Speed of analog computers is less than the digital computers.	Speed of digital computers is more than the analog computers.
03.	Analog computer has very low or limited memory and it can store less amount of data.	Digital computer has very big memory it can store large amount of data.
04.	Analog computer has no state.	Digital computer has On and Off these 2 steps.
05.	Analog computers are less reliable than digital computers.	Digital computers are more reliable than analog computers.
06.	Its performance is comparatively low.	Its performance is very high.
07.	Its speed of processing is not so high.	Its speed of processing is very high.
08.	Analog computers depends upon physical variations.	Digital computers does not depend upon physical variations.
09.	It provides results with less accuracy as compared to digital computers.	It provides results with higher accuracy as compared to analog computers.
10.	Analog computers are difficult to use.	Digital computers are not so difficult to use.
11.	Analog computers have complex architecture.	Digital computers do not have so complex architecture like analog computers.
12.	Readability of analog computer is low.	Readability of digital computer is high.
13.	Analog computers show the result in terms of voltage signals.	Digital computers show the result in computer display screen.
14.	Analog computers employs analog encoding.	Digital computers employs digital encoding.
15.	Power consumption is high.	Power consumption is low.
16.	They are usually special purpose devices.	It can be general purpose devices.
17.	Examples includes analog clock and thermometer etc.	Examples includes Digital laptop, digital camera, digital watches etc.

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Hybrid Computer

Hybrid computer has features of both analogue and digital computer. It is fast like an analogue computer and has memory and accuracy like digital computers. It can process both continuous and discrete data. It accepts analogue signals and convert them into digital form before processing. So, it is widely used in specialized applications where both analogue and digital data is processed. For example, a processor is used in petrol pumps that converts the measurements of fuel flow into quantity and price. Similarly, they are used in airplanes, hospitals, and scientific applications.

Advantages of using hybrid computers:

• Its computing speed is very high due to the all-parallel configuration of the analogue subsystem.
• It produces precise and quick results that are more accurate and useful.
• It has the ability to solve and manage big equation in real-time.
• It helps in the on-line data processing.