Computer Sciences

Computer ! an amazing machine! We are living in the computer age today and most of our day activities cannot be a accomplished without using computers. sometimes knowingly and sometimes unknowingly we use computers. Whether we have to withdraw money from the ATM(Automated Teller Machines, retranslated as Any Time Money), publish a newsletter, drive a motorbike, design a building or even a new dress, go to a grocery shop and by from cookies to types for our car – all involve computer in one way or the other.
We are breathing in the computer age and gradually computer has becomes such are breathing in the computer age and gradually computer has become such a dire necessity of life that it is difficult life without it.
Computer is affecting every sphere of our life. Be it government, business, education, legal practice, entertainment, defense or home – computer has becomes an indispensable and multipurpose tool.

Computers have shaken up the world. They have made us dependent upon them. We expect them to be present at every place: be it the reservation counter, the microwave cooking or even driving a car. Now that computers have moved in our society so rapidly, one needs, at least the basic computer skills to pursue one’s career goals and function effectively and effectively. We can say that computer literacy is the need of today and voice of tomorrow to survive on the fast changing world of computers.

For most of the people computer literacy is restricted to using the keyboard for typing a document or making use of it for the calculations. But this is not enough. One must know the fundamental concept about what computers constitute of and how the they work. Take an example, you drive a motorbike and you take it for the servicing. There is one way that you tell the service boy to service the motorbike and I will collect it in the evening. The another way could be that you tell him that, apart from servicing, please change the engine oil and clean the carburetor too. This way the service man would be more careful while doing the job of your motorbike and you too will be able to solve at least some of the small problems when the machine is not available. The lack of knowledge can cause mistakes while using the computer also. Sometimes this lack of knowledge can cause mistakes while using the computer also. Lack of knowledge can cause mistakes while using the computer also. Sometimes this lack of knowledge cause some fear in the people. This is termed as CYBERPHOBIA

Computer Definition



For most of the people, computer is a machine used for calculations or computation, but actually, it is much more than that. Precisely, “Computer is a device for performing arithmetic and logical operations”, or “Computer is a device or flexible machine to process data and convert it into information”.
Now, in the above two definitions, three words are tricky that need some explanations. Let us start with logical operation-these are the type of operation in which decision(s) is/are involved. Data is simply raw fact or figure collected whereas the information is what one gets after processing the data. Information is always useful and meaningful for the user. Let us consider and example in which marks of various subjects are collected for a particular group of students. Now, these marks independently(data) are of no use as such for the class teacher, but once she he adds the marks of all the students and calculates their respective percentages, this becomes information and it serves her/him in finding out the answer for the queries like Who has 1st in the class? Or How many people have got distinctions in the class? What is the overall performance of the class? “A program is a set of instructions telling the computer what to do.”

Broadly computer can be said to be made up of hardware and software. The computer hardware(actual machine) is defined in such a way that it does whatever the software(computer programs) tells it to do.
There are 4 basic operation which a computer performs irrespective of the program which is running on it. They are classified as:-











1-Input :-





This is for the purpose of inserting or feeding data into the computer by means of an input device like keyboard.
















2- Processing:-





Some kind of processing is done in the computer to take out or transform the data in some way.


















3- Output:-






The computer produces output on a device, such as printer or out or monitor, that show the result of processing operation .












4- Storage:-










The computer stores the result of processing operations for future use in some storage device like hard disk or floppy disk.

In recent years, the computer industry has grow at a phenomenal pace. In a short time of 35 years or so computers have improved tremendously. In the last decade the speed of computer has increase. The cast per unit of calculating has gone down by 500 times. The storage capacity is increasing so fast that now it seems that nothing is impossible to store. Large data can be stored in very small devices.



First Generation of computer(1942-1955):-


Until 1951, electronic computers were exclusive possession of scientists and the military. Till then nobody tried to use them for business purpose. The idea of marketing them was conceived mushily and Eckert, creators of ENIAC’S. as US census bureau was already using IBCP cards, they were the pioneers in US buying this computer for the first time in 1951. the company created by M and ETS become UNIVAC division of Sperry and Corporation (later known as UNISYS).


Computer belonging to this generation had the following characteristics:

1. Comparatively large in size as composed to present day computers.
2. Generated lot of heat, they were not consistent and reliable as the valves tended to fall frequently.
3. low capacity internal storage.
4. individual, non-related models.
5. processors operated in the milliseconds speed range.
6. internal storage consisted of magnetic drum and delay lines.






Second Generation (1955-1964):

FGC were very unreliable, mainly because of vacuum tubes which kept on burning out. Users had to be prepared all the time with dizen of extra tubes to replace them. The computers of this generation were characterized by the use of Solid State devices(transistors) misted of vacuum tubes. Transistorized circuits were smaller, generated little heat, were expensive and consumed less power than vacuum tube circuits and were much greater in processing capacity.

Since transistors had a faster switching action, this generation than first generation computers. The use of magnetic cores as the primary internal storage medium and the introduction of removable magnetic disc pack were other major developments of the second generation. Although magnetic tapes were still used commonly. These computers had built in error detecting devices and more efficient means were developed to input and retrieve from the computer.



Some of the popular models in this generation of computer systems, we IBM-1401, IBM-1620, BURROUGHS B-200 SERIES, HONEY-WELL H-400, these computers were used for business applications.



Third Generation of Computer(1964-1975)

A revolution in the computer developments took place with the development of integrated circuits (IC) on a single silicon chip. In 1958, jack St Clair Kebly and Robert Noyce invented the first IC. IC incorporated number of transistors and electronic circuits on a single wafer or chip of silicon IC is called chip beause of the way they are made. They are also called as semi conductors as combining layers of materials that have varying capacity to conduct electricity from them.

This ushered in the third generation of computer systems in 1964. the integrated circuits enhanced considerably the processing capability of placing 12 or more logic gates on a single chip was developed into a well-defined technology was redefined to a point where hundreds or more gates could be placed on a chip of silicon and incorporated as functional logic block in an overall system.


Computers of this generation have the following characteristicts:


1. Smaller in size as compared to second generation computers.
2. Higher capacity internal storage.
3. Remote communication facilities.
4. Multiprogramming facilities.
5. Reduced cost of access storage.
6. Processors, which operate in nanosecond speed range.
7. Use of high level languages such as COBOL.
8. Wide range of optional peripherals.




Fourth Generation of Computer (1975-1989)


The 1970’s marked the beginning of a new generation of computers, produced by computer giants like IBM, ICL, CNR and Burrought. From design viewpoint, the new generation provided increased input-output capability, longer component life as well as greater system reliability. From the functional view point, new powerful language were developed to broaden the use of multiprogramming and multiprocessing and major shift from batch processing to on line, remote interactive processing.


The development of microprocessor chip, which contains an entire Central Processing Unit(CPU) on a single silicon chip led to the mushroom growth of inexpensive computers. They are not computers by themselves but they can perform all the functions of arithmetic logic unit and control units of the CPU. When these microprocessor are connected with memory and input-output devices, they become microcomputers.

The use of very large integrated circuits (VLSI) has made the froth generation (micro) computers very compact, much less expensive, faster, more reliable and of much greater data processing capacity than equalized third generation computers.

Some computers belonging to fourth generation are DEC-10, STAR-1000, PDP-11 AND APPLE Series Personal computers.




Fifth Generation Computers (1989-Present)

Till fourth generation of computers, the major stress was on improving the hardware from values to transistors and then to integrated circuits, which resulted in miniaturization and fast speed of computers. Hardware, the lack of thinking power has forced the scientists to work further for fifth generation computers.

The concept of “Artificial Intelligence” is being used in these computers and Japanese call them “Knowledge Processors”. Automatic programming, computational logic, pattern recognition and control of robots, the processes and which need skill and intelligence are examples of Artificial Intelligence. These computers, when developed, will have be able to execute billion of instructions per second and will have unimaginable storage capacities. The present day high level languages will become obsolete on these machines and new computer language and related software will be needed.

Computers of this generation have the following characteristics:

1.Easy to computers with high intelligence and natural human input and output mechanism;

2.Reliable and efficient software development by new languages, new computer architectures and systems software which overcome previous problems;

3.Improved overall functions and performance aimed at making computers smaller, lighter, faster, faster, of greater capacity, more flexible and more reliable

Introduction-

The processing unit in a computer interest instructions given in a programs and carries out the instructions. Processors are designed to interpret a specified number of instruction codes. Each instruction code is a string of binary digits. All processors have input/outputs instructions, arithmetic instructions, to manipulate characters. The number and type of instructions available differ from processor to processor.

A memory or store is required in a computer to store programs and the data processed by programs. A memory is made up of a large number of cells, with each cell capable of storing one bit. The cells may be organized as a set of addressable words, each word storing a sequence of bits. In one such address of the word. This organization, called a Random Access Memory (RAM), is used as the main memory of computers. Another organization arranges cells in a linear sequence to from a serial access memory.

The Central Processing unit is the brain of the computers system. The input and output devices may vary for different application, but there is only one CPU for a particular computer. The specifications of a computer are basically characterized by its Central Processing Unit.

The CPU processes the data it receives as input (either through input devices or through the memory). As mentioned earlier the CPU receives the data in the from of binary bits, which it can understand.

1. the CPU can perform arithmetic calculation such as addition, subtraction etc.
2. the CPU can perform logical decisions.
3. The CPU with the help of other devoices can perform data transmission.
4. The CPU can perform manipulating tasks such as word processing.
5. After performing the required task the CPU may place results in memory or send results to the output device according to the instruction given to it.



The central processing unit can be further divided into:


1. Arithmetic Logic Unit(ALU)-

As the name may indicate the arithmetic logic unit performs all arithmetic and logic calculations on the data it receives.


2. Arithmetic Calculations-

The arithmetic calculations may be addition, subtraction, multiplication, division, exponentiation etc.

3. Logical Calculation-

Logical calculations are basically decision making statements. For example, A>B, decides whether is A is greater B or not; IF A is greater than B the statement is true and logical ‘1’ would be generated, otherwise a logical ‘0’ would be generated. Some logical decide the further routing of the program.

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Labels: fundamentals of computer
Control Unit –



Control Unit –

The control unit controls the entire operations of the computer and the CPU. It controls all the other devices connected the CPU. Input devices, output devices, auxiliary Memory etc. hence, the control acts as the never centre of the computer.
The control unit upon receiving an instruction decides what is to be done with it. That is, whether it is to be sent to the ALU for further processing or to the output devices or to the memory etc. in other words the control unit coordinates and controls all hardware operations.

The control unit has an electronic clock that transmits electronic pulses at equal interval of time. The control unit gives instructions to other devices based upon these pulses. Suppose there are three instructions to be performed. Let the first instructions take three clock pulses to complete; when the fourth clock pulse is received the control unit would start processing the second instruction and so on. Suppose an instruction takes three and for the fourth clock pulse to complete and take up the next instruction with the fifth clock. Pulse.

Registers –

The CPU consists of a set of registers which are used for various operations during the execution of instructions. CPU needs registers for storing instructions as well as for storage and manipulation of temporary results.

1. Fetch: To bring the instructions from main memory into the instruction register.

2. Decode: Decoding means interpretation of the instruction to decide which course of action is to be taken for execution of the instruction and what sequence of control singles must be generated for it.



3. Execute: The instruction is execute after the fetching of operands is complete. The control unit is responsible for sequencing the steps necessary to complete.