CLASSIFICATIONS OF COMPUTERS

There is an almost bewildering variety of computers, and the number of models available is rapidly growing. To some extent this variety is redundant; many machines are similar in capacity. But to a greater extent the variety of computers is related to important differences in capacity and functions.

The distinctions among the various categories of computers has been subject to controversy. Computers may be classified according to their purpose, according to the kind of processing they do or types of data they use, and also according to the size of the machine and the speed of its internal operations.

Speed of operation is often the most important consideration in deciding which equipment to choose for a particular task. With today's machines, It is generally true that the bigger the machine, the faster the operating speed.

CLASSIFICATIONS OF COMPUTERS BY PURPOSE

Digital computers may be utilized for either special or general purposes.

1. General-Purpose Computers - This machines have the capability of dealing with variety of different problems, and are able to act in response to programs created to meet different needs. A general-purpose computer is one that has the ability to store different programs of instruction and thus to perform a variety of operations.

2. Special-Purpose Computers - as to the name implies, is designed to perform one specific tasks. The program of instructions is built into, or permanently stored in the machine. Specialization results in the given task being performed very quickly and efficiently. Most special purpose computers have the capability of performing just one task. They are frequently referred to us "dedicated," because of their limitations to the specific task at hand.

CLASSIFICATION BY TYPE OF DATA HANDLED

There are essentially two different types of computer processing. Each is made possible by a different kind of circuitry , and each is suitable for different purposes.

1. Analog Computers - The name analog comes from the word "analogous", meaning similar. Analog computers are used for scientific, engineering, and process control purposes. Because they deal with quantities that are continuously variable., they give only approximate results. This types of computer provides an analog or simulation of the object or system it represents. It is especially useful for solving problems that involve relationships between variable quantities in systems that change with time. The analog compute may express changing relationships in output in the form of graphs. It is able to create such pictures because it responds to changes in electrical voltages that match changes in variable quantities.

2. Digital Computers - Is a machine the specializes in counting. It operates by counting values that are discrete, or separate and distinct, unlike the continuous quantities that can be measured by the analog computer. Digital Computers are used for both business data processing and accuracy. The basic operation performed by a digital computer is addition. It can store the sums of addition problems as they accumulate, and can complete a single calculation in a fraction of a nanosecond. The digital computer is capable of storing data as long as needed, performing logical operations, editing input data, and printing out the results of its processing at hight speed.

3. Hybrid Computers - Although both analog and digital computers are extremely used in widely accepted in various industries, manufacturers have to attempted to designed a computer that combines the best features of both types. This special-purpose machine called a hybrid, computer, combines the measuring capabilities of the analog computer and the logical and control capabilities of the digital computer. It offers an efficient and economical method of working out special types of problems in science and various areas of engineering. Some Hybrid machines contain special equipment to convert analog voltages into digital voltages,and vice-versa.

CLASSIFICATION OF COMPUTERS ACCORDING TO CAPACITY

The term "capacity" refers to the volume of work or the data processing capacity a computer can handle. Their performance is judged by the:

1. Amount of data that can be stored in memory

2. speed of internal operation of the computer

3. number and type of of peripheral device.

4. amount and type of software available for use with the computer

The capacity of early generation computers were determined by their physical size- the large the size, the greater the volume. In computer terms, size and speed of operation are at present proportionate to each other. Generally, though, recent, technology is tending to create smaller machines, making it possible to package equivalent speed and capacity in a smaller format.

Computer System Classification

1.     MICROCOMPUTERS= The mass production of silicon chips since 1971 has made it possible to put a "brain"into all sorts of machines. One such machine is the microcomputer. This machines has takes fullest advantage of the use of large-scale integration on silicon chips. The microprocessors literally contain a computer on a chip that can pass through the eye of needle. Microcomputers memories are generally made of semiconductors fabricated on silicons chips. It is a digital computer system under the control of a stored program that uses a microprocessor, a programmable read-only memory (ROM), and a random-access memory (RAM), The ROM defines the instructions to be executed by the computer while RAM is the functional equivalent of computer memory.

2.     MINICOMPUTERS= Technological advances in the 1960's enabled manufactures to respond to the growing demand for a similar stand-alone machine, the minicomputer, to handle task that large computers could not perform economically. Minicomputer system (or small mainframe computers) provide faster operating speeds and larger storage capacities than microcomputers systems. They can support a large number of high-speed input/output devices. Several desk drives can be used to provide online access to large data files as required for direct- access processing.

Operating system developed for minicomputer systems generally support both multiprogramming and virtual storage. This means that many programs can be run concurrently. This type of computer system is very flexible and can be expanded to meet the needs of users.

Minicomputers usually have from 8k to 256K memory storage locations, and a relatively established applications software. although the minicomputer is not as powerful as the medium or large-size computer, it is quite close.

3.     MEDIUM-SIZE COMPUTERS= it provide faster operating speeds and larger storage capabilities than small computer systems. They can support a large number of high-speed input-output devices, and several disk drives can be used to provide online access processing. Also support both multiprogramming and virtual storage. This allows the running of a variety of programs concurrently.

Medium-size computer system are very flexible; they can be expanded to meet the needs of users. The possibility of increasing the data processing capability of a computer by adding devices, such additional memory, and other peripheral devices, is called expandability.

4.     LARGE COMPUTERS=are the ultimate in system sophistication, flexibility, and speed. They usually contain full control systems with minimal operator intervention. Large computer systems range from single-processing configurations to nationwide computer based networks involving general large computers. Large computers have storage capacities from 512K to 819K, and these computers have internal operating speeds measured in terms of nanoseconds, as a compared to smaller computers where speed in terms of microseconds.

5.     SUPERCOMPUTERS= The biggest and fastest machines today are the supercomputers that are used when billions or even trillions of calculations are needed. These machines are essential for applications ranging from nuclear weapon to accurate weather forecasting.

Supercomputers are machines that have capabilities far beyond even the traditional large scale systems. Their speed is in the 100-million-instructions-per-second range.

Each generation of computer is characterized by a major technological development that fundamentally changed the way computers operate, resulting in increasingly smaller, cheaper, more powerful and more efficient and reliable devices.
The history of computer development is often referred to in reference to the different generations of computing devices. Each generation of computer is characterized by a major technological development that fundamentally changed the way computers operate, resulting in increasingly smaller, cheaper, more powerful and more efficient and reliable devices. Read about each generation and the developments that led to the current devices that we use today.
Key Terms: computer, magnetic drums, binary, integrated circuit,  semiconductor, nanotechnology

First Generation (1940-1956) Vacuum Tubes

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The first computers used vacuum tubes for circuitry and magnetic drums for memory, and were often enormous, taking up entire rooms. They were very expensive to operate and in addition to using a great deal of electricity, generated a lot of heat, which was often the cause of malfunctions.

First generation computers relied on machine language, the lowest-level programming language understood by computers, to perform operations, and they could only solve one problem at a time. Input was based on punched cards and paper tape, and output was displayed on printouts.

The UNIVAC and ENIAC computers are examples of first-generation computing devices. The UNIVAC was the first commercial computer delivered to a business client, the U.S. Census Bureau in 1951.

Second Generation (1956-1963) Transistors

Transistors replaced vacuum tubes and ushered in the second generation of computers. The transistor was invented in 1947 but did not see widespread use in computers until the late 1950s. The transistor was far superior to the vacuum tube, allowing computers to become smaller, faster, cheaper, more energy-efficient and more reliable than their first-generation predecessors. Though the transistor still generated a great deal of heat that subjected the computer to damage, it was a vast improvement over the vacuum tube. Second-generation computers still relied on punched cards for input and printouts for output.
Second-generation computers moved from cryptic binary machine language to symbolic, or assembly, languages, which allowed programmers to specify instructions in words. High-level programming languages were also being developed at this time, such as early versions of COBOL and FORTRAN. These were also the first computers that stored their instructions in their memory, which moved from a magnetic drum to magnetic core technology.
The first computers of this generation were developed for the atomic energy industry.

Third Generation (1964-1971) Integrated Circuits

The development of the integrated circuit was the hallmark of the third generation of computers. Transistors were miniaturized and placed on silicon chips, called semiconductors, which drastically increased the speed and efficiency of computers.
Instead of punched cards and printouts, users interacted with third generation computers through keyboards and monitors and interfaced with an operating system, which allowed the device to run many different applications at one time with a central program that monitored the memory. Computers for the first time became accessible to a mass audience because they were smaller and cheaper than their predecessors.

Fourth Generation (1971-Present) Microprocessors

The microprocessor brought the fourth generation of computers, as thousands of integrated circuits were built onto a single silicon chip. What in the first generation filled an entire room could now fit in the palm of the hand. The Intel 4004 chip, developed in 1971, located all the components of the computer—from the central processing unit and memory to input/output controls—on a single chip.
In 1981 IBM introduced its first computer for the home user, and in 1984 Apple introduced the Macintosh. Microprocessors also moved out of the realm of desktop computers and into many areas of life as more and more everyday products began to use microprocessors.
As these small computers became more powerful, they could be linked together to form networks, which eventually led to the development of the Internet. Fourth generation computers also saw the development of GUIs, the mouse and handheld devices.

Fifth Generation (Present and Beyond) Artificial Intelligence

Fifth generation computing devices, based on artificial intelligence, are still in development, though there are some applications, such as voice recognition, that are being used today. The use of parallel processing and superconductors is helping to make artificial intelligence a reality. Quantum computation and molecular and nanotechnology will radically change the face of computers in years to come. The goal of fifth-generation computing is to develop devices that respond to natural language input and are capable of learning and self-organization.