CLASSIFICATION OF COMPUTERS

COMPUTER AND ITS CLASSIFICATION

Computer

“The Computer is an Electronic Device which accepts the input data processing according to their Instruction and it gives output result”. According to Technology used Computer can be classified on the basis of different factors such as circuits, the task performance capabilities, purpose, size and storage capacity.

Classification of computers:-

Computers may be classified based on the following: -

i.                    Operating principles (based on their construction and working)

ii.                  Applications

iii.                Size and capability (or classification into micro, mini, mainframe and supercomputers)

iv.                Number of Microprocessors

v.                  Word length and                                             vi.        Number of users CLASSIFICATION BASED ON OPERATING PRINCIPLES

i)          Classification based on Operating Principles

Based on the operating principles, computers can be classified into one of the following types: -

A.                  Digital Computers

B.                  Analog Computers

C.                  Hybrid Computers

A.                  Digital Computers: - A computer that performs calculations and logical operations with quantities represented as digits, usually in the binary number system. Operate essentially by counting. All quantities are expressed as discrete or numbers. Digital computers are useful for evaluating arithmetic expressions and manipulations of data (such as preparation of bills, ledgers, solution of simultaneous equations etc.) It works with digit 0 & 1.

B.        Analog Computers:- An analog computer is a form of computer that uses the continuously changeable aspects of physical phenomena such as electrical, mechanical, or hydraulic quantities to model the problem being solved. In contrast, digital computers represent varying quantities symbolically, as their numerical values change. It works on supply of continuous signal & display continuous speed.

C.         Hybrid Computers:- are computers that exhibit features of analog computers and digital computers. A hybrid computer system setup offers a cost effective method of performing complex simulations. The digital component normally serves as the controller and provides logical operators, while the analog component normally serves as a solver of differential equations. Areas of application are refineries, nuclear power plant mines etc.

CLASSIFICATION BASED ON AREA OF APPLICATION

Classification based on area of applications

Modern computers depending upon their applications are classified as: -

a.                   Special Purpose Computers

b.                   General Purpose Computers

a.)                Special Purpose Computers: - A 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 posses unnecessary options and is less expensive. Examples are computers used for weather forecasting, for satellite launching, medical diagnostics etc.

 b)  General Purpose Computers: - A General Purpose computers are designed to meet the needs of many different applications. 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. Examples are computers used in schools, colleges & offices.

CLASSIFICATION BASED ON SIZE AND CAPABILITY

Classification digital Computer based on size and Capability

Based on size and capability, computers are broadly classified into

a.                   Microcomputers(Personal Computer)

 A microcomputer is the smallest general purpose processing system. The older pc started 8 bit processor with speed of 3.7MB and current pc 64 bit processor with speed of 4.66 GB. Micro computers is a digital computer whose processing unit consists of one or more microprocessors, one or more input / output units and sufficient memory to execute instructions. They are used in schools, homes, office etc. Some popular micro computers are IBM system 123, Apple 2 and 3 etc.

Examples: -     IBM PCs, APPLE computers

Microcomputer can be classified into 2 types:

1.       Desktops         2.       Portables

The difference is portables can be used while travelling whereas desktops computers cannot be carried around.

The different portable computers are: -

1)         Laptop

2)         Notebooks

3)         Palmtop (hand held)

4)         Wearable computers

Laptop: - this computer is similar to a desktop computers but the size is smaller. They are expensive than desktop. The weight of laptop is around 3 to 5 kg.

Notebook: - These computers are as powerful as desktop but size of these computers are comparatively smaller than laptop and desktop. They weigh 2 to 3 kg. They are more costly than laptop.

Palmtop (Hand held): - They are also called as personal Digital Assistant (PDA). These computers are small in size. They can be held in hands. It is capable of doing word processing, spreadsheets and hand writing recognition, game playing, faxing and paging. These computers are not as powerful as desktop computers. Ex: - 3com palm V.

Wearable computer: - The size of this computer is very small so that it can be worn on the body. It has smaller processing power. It is used in the field of medicine. For example pace maker to correct the heart beats, Insulin meter to find the levels of insulin in the blood.

b).    Workstations:- It is used in large, high-resolution graphics screen built in network support, Engineering applications(CAD/CAM), software development desktop publishing

Ex:  Unix and windows NT.

b)         Minicomputer: -         A minicomputer is a medium-sized computer. That is more powerful than a microcomputer. In size and power, minicomputers lie between workstations and mainframe computers. These computers are usually designed to serve multiple users simultaneously (Parallel Processing). They are more expensive than microcomputers. Mini Computers are medium scale computer in the sense that they are faster than micro computers. These computers have large storage capacity and can support up to 120 terminals. Mini computers have operating systems with multitasking and network capabilities enabling them to serve more than one user e-g 1BM, PDP-1 etc.

            Examples:        Digital Alpha, Sun Ultra.

c)         Mainframe computers: - A very large and expensive computer capable of supporting hundreds, or even thousands, of users simultaneously. In the hierarchy that starts with a simple microprocessor (in watches, for example) at the bottom and moves to supercomputers at the top, mainframes are just below supercomputers. Computers with large storage capacities and very high speed of processing (compared to mini- or microcomputers) are known as mainframe computers. They support a large number of terminals for simultaneous use by a number of users like ATM transactions. They are also used as central host computers in distributed data processing system. Mainframe computers are general’s purpose computers which are designed to handle all type of scientific and business application with large volume of data instruction and information .These can have large online secondary storage capacity and can support, variety of peripheral devices like magnetic taps driver, hard desk drivers, visual display unit and telecommunication terminals e.g. CDC 600, VAX 8842, IBM 3090/600, IBM 4381
Mainframe Computers are mainly used for the following applications:

1. Railways and Airlines Reservation

2.  Banking Application

3. Commercial Application

            Examples: -     IBM 370, S/390.

d)         Supercomputer: -    The fastest and most powerful type of computer Supercomputers are very expensive and are employed for specialized applications that require immense amounts of mathematical calculations. Supercomputers have extremely large storage capacity and computing speeds which are many times faster than other computers. A supercomputer is measured in terms of tens of millions Instructions per second (mips), an operation is made up of numerous instructions. The supercomputer is mainly used for large scale numerical problems in scientific and engineering disciplines such as Weather analysis. These computers are characterized by their large size and are very high processing speed and are generally used for complex and scientific applications these are most powerful computer and are very expensive .These can execute instructions in the large of 5 billion instructions per second.
e.g CRAY3, NEC-500, PARAM9000, PARAM10000, ANURAG.
These computers are mainly used for following application:
1. Weather Forecasting.
2. Petroleum exploration and production.

            Examples: -     IBM Deep Blue

CLASSIFICATION BASED ON NUMBER OF MICROPROCESSORS

Classification based on number of microprocessors

Based on the number of microprocessors, computers can be classified into

a.                   Sequential computers and

b.                   Parallel computers

a)         Sequential computers: -        Any task complete in sequential computers is with one microcomputer only. Most of the computers (today) we see are sequential computers where in any task is completed sequentially instruction after instruction from the beginning to the end.

b)         Parallel computers: - The parallel computer is relatively fast. New types of computers that use a large number of processors. The processors perform different tasks independently and simultaneously thus improving the speed of execution of complex programs dramatically. Parallel computers match the speed of supercomputers at a fraction of the cost.

CLASSIFICATION BASED ON WORD LENGTH AND NUMBER OF USERS

Classification based on word-length

            A binary digit is called “BIT”. A word is a group of bits which is fixed for a computer. The number of bits in a word (or word length) determines the representation of all characters in these many bits. Word length lies in the range from 16-bit to 64-bits for most computers of today.

Classification based on number of users

Based on number of users, computers are classified into: -

a.           Single User: - Only one user can use the resource at any time.

b.           Multi User: - A single computer shared by a number of users at any time.

c.            Network: - A number of interconnected autonomous computers shared by a number of users at any time.

Generation Of Computers

Generation  of  Computers

The history of computer development is often in reference to the different generations of computing devices. Each of the five generations of computer is characterized by a major technological development that fundamentally changed the way computers operate. Most developments resulted in increasingly smaller, cheaper, more powerful & more efficient computing devices. Generation of computers is mainly classified by 5 different generations. These are:

1)                       First Generation Computers(1949-55) :

The 1^st generation emerged during 1949 & lasted till 1955. The 1^st large electronic computer was ENIAC which used high speed vacuum tubes & was invented in 1946. It was mainly designed to calculate the trajectories of missiles. It took about 200 ms to perform addition & about 2800 ms to perform multiplication. Later on, EDSAC was developed in 1949 which used mercury delay lines for storage. Also, UNIVAC 1 was designed during this period, which also used vacuum tubes. Generally, these computers used more than 10,000 tubes & so, power dissipation was very high. These were mainly used in the field of science & engineering. Programming was mainly done in machine language. The concept of operating system wasn’t introduced yet. In this generation punched cards, paper tapes & magnetic tapes were used as input & output devices.  The computers in this generation were very costly & not within the reach of common people. Also, they were quite bulky which made them non-portable.

2)                       Second Generation computers(1956-65)

The 2^nd generation evolved during 1956 & lasted till 1965. This generation witnessed a revolution in electronics world by introduction of transistors instead of previously used vacuum tubes. Transistors were more reliable & they took very less space than tubes. During this period, magnetic cores were developed for storage. Also, magnetic disk storage was invented. High level programming languages like COBOL, FORTRAN etc. were developed. With higher speed CPUs, magnetic tapes etc., the operating systems were developed (Good Batch OS). The 2^ndgeneration computers consumed less electricity & generated less heat in comparison to 1^st generation computers. Also, they were faster & cheaper than 1^st generation computers. Commercial applications were improved during this generation. The 2^ndgeneration computers supported machine & assembly language. 80% of installed computers were in business & industry. This generation also paved the way for new professions like system analyst, programmers etc. Some computers of this generation were IBM 1620, IBM 7094, UNIVAC 1108 etc.

3)                       Third generation computers(1966-75):

This generation emerged during 1966 & lasted till 1975. This generation witnessed the introduction of silicon transistors instead of previously used germanium transistors. Integrated circuits(IC’s), which consisted of resistors, transistors & capacitor came into existence. From small scale IC’s, consisting of 10 transistors per chip, it developed to medium scale IC’s which contained 100 transistors per chip. Thus, reliability & switching speed went up by a factor of 10 and space & power dissipation was reduced by a factor of 10. These all led to the emergence of extremely powerful CPUs which could carry about 1 million instructions per second. Programming languages were improved. High level languages like FORTRAN II to IV, COBOL, PASCAL, BASIC etc. were used during this generation. Also, a new operating system, known as Time-Sharing OS came into existence. The 3^rdgeneration computers needed lesser maintenance, consumed less electricity, generated less heat, were smaller in size & cheaper than previous generation computers. Some computers of this generation were IBM-360 series, Honeywell-6000 series, PDP etc.

4)                       Fourth Generation computers:

This generation emerged during 1976 & lasted till 2000. This generation witnessed introduction of microprocessor chips. From middle scale IC’s, the technology developed to large & very large scale IC’s (VLSI), which consisted of about 50,000 transistors per chip. It led to emergence of extremely powerful PCs. Cost of computers went down rapidly. It was now within the reach of every professional. Cost of hard disks also went down & high capacity secondary storage was introduced. It saw the coming age of UNIX OS & Time-Shared interactive systems which were more reliable & user friendly. There was a relentless increase in the speed of microprocessors & size of main memory, which increased by a factor of 4, every 3 years. Also, DVD ROMs & writable CDs were developed. A large no. of computers got connected with Internet, due to which WWW (World Wide Web) came into existence. It resulted into emergence of Object Oriented language called JAVA. Later on, C, C++ was also developed. Now, the computers were within reach of common people too. Some computers of this generation were DEC 10, STAR 1000, PDP 11 etc.

5)                       Fifth Generation computers:

The 5^th generation has revolutionized whole world of digital electronics. It has paced up the development of computers. There has been a relentless increase in the no. of transistors on a single chip. This generation witnesses a rapid increase in the bandwidth of network & consequently, Internet. It offers mobility to its users & provides them a good multimedia experience. It is mainly concerned with Parallel processing hardware & Artificial Intelligence (AI).  In 5^thgeneration VLSI became ULSI (Ultra Large Scale Integration), which results in the production of microprocessor chips having 10 million electronic components. AI (Artificial Intelligence) is an emerging branch, which interprets means & method of making computers think like human beings. All high level-languages like C & C++, JAVA, .NET etc. are used in this generation. This generation is witnessing development of natural language processing, advancement in parallel processing, advancement in superconductor technology & so many other technological advancements in all the fields. It provides more user-friendly interface with multimedia features. More powerful & compact computers are available at cheaper rates. Some computers of this generation are Laptop, PCs, Notebook etc.