HISTORY OF COMPUTER

 

History of Computer

History of computer could be traced back to the effort of man to count large numbers. This process of counting of large numbers generated various systems of numeration like Babylonian system of numeration, Greek system of numeration, Roman system of numeration and Indian system of numeration. Out of these the Indian system of numeration has been accepted universally. It is the basis of modern decimal system of numeration (0, 1, 2, 3, 4, 5, 6, 7, 8, 9). As we know computer does not understand the decimal system and uses binary system of numeration for processing. We will briefly discuss some of the path-breaking inventions in the field of computing devices.

1. Calculating Machines: It took generations for early man to build mechanical devices for counting large numbers. The first calculating device called ABACUS, was developed by the Egyptian and Chinese people. The word ABACUS means calculating board. It consists of sticks in horizontal positions on which are inserted sets of pebbles.It has a number of horizontal bars each having ten beads. Horizontal bars represent units, tens, hundreds, etc.

2. Napier’s bones : English mathematician John Napier built a mechanical device for the purpose of multiplication in 1617 AD. The device was known as Napier’s bones.

3. Slide Rule: English mathematician Edmund Gunter developed the slide rule. This machine could perform operations like addition, subtraction, multiplication, and division. It was widely used in Europe in 16th century.

4. Pascal’s Adding and Subtraction Machine: You might have heard the name of Blaise Pascal. He developed a machine at the age of 19 that could add and subtract. The machine consisted of wheels, gears and cylinders.

5. Leibniz’s Multiplication and Dividing Machine: The German philosopher and mathematician Gottfried Leibniz build around 1673 a mechanical device that could both multiply and divide.

6. Babbage’s Analytical Engine: It was in the year 1823 that a famous English man Charles Babbage built a mechanical machine to do complex mathematical calculations. It was called difference engine. Later he developed a generalpurpose calculating machine called analytical engine. You should know that Charles Babbage is called the Father of computers.

7. Mechanical and Electrical Calculator: In the beginning of 19th century the mechanical calculator was developed to perform all sorts of mathematical calculations and it was widely used till 1960. Later the routine part of mechanical calculator was replaced by electric motor. It was called the electrical calculator.

8. Modern Electronic Calculator: The electronic calculator used in 1960s was run with electron tubes, which was quite bulky. Later it was replaced with transistors and as a result the size of calculators became too small. The modern electronic calculators can compute all kinds of mathematical computations and mathematical functions. It can also be used to store some data permanently. Some calculators have inbuilt programs to perform some complicated calculations.

Development of Computer

1600 A.D.– NAPIER BONES: Another counting device is Napier Bones, “John Napier. a Scottish Mathematician, invented it. The “bones” were strips of ivory with numbers written in them. When the bones were arranged properly. the user could read the numbers in adjacent columns to get the answer of a multiplication operation.

1642 A.D– ADDING MACHINE– BLAISE

PASCAL– PRANCE: The well known French Scientist and Mathematician, Blaise pascal invented the first machine which could add, carry digits automatically. he was only nineteen years old at that time. His machine was so revolutionary that the principle behind it is still used in most of the machanical counters being used today.

1692 A.D.– MULTIPLYING MACHINE- COTTFRIED LEIBNITZ- GERMANY: Gottfried improved upon Pascal’s machine and introduced a mechanism to carry out automatic multiplication of numbers. Leibnita is best known for his work with Sir Isaac Newton in developing a branch of Mathematics, known as Calculus. The calculator in vented by him could add, subtract, multiply and divide accurately. It could even perform square root function, although not always accurately.

1813 A.D. – DIFFERENCE ENGINE– CHARLES BABBAGE– ENGLAND: Since early 19th century, Charles Babbage, an Englishman, had been working on the development of a machine, which could perform complex calculations In 1813 A.D. he invented the ‘Difference Engine’ which could perform complex calculations and print them out as well. This machine was a steam powered machine.

EARLY 1800’S JACQUARD LOOM- JOSEPH MARIE JACQUARD

In the early nineteenth century, a French weaver Joseph marie Jacquard developed a programmable loom, which used large cards and holes punched in them to control the pattern automatically. The output was a thick rich cloth with repetitive floral or geometric patterns.

Jacquard patterns are still produced to this day. Others adapted the punched cards and used as the primary form of input. They were used till about 20 – 25 years ago.

APPLICATIONS OF COMPUTER

Applications of Computers

Computers have their application or utility everywhere. We find their applications in almost every sphere of life–particularly in fields where computations are required to be done at a very fast speed and where data is so complicated that the human brain finds it difficult to cope up with. As you must be aware, computer now-a-days are being used almost in every department to do the work at a greater speed and accuracy. They can keep the record of all the employees and prepare their pay bill in a matter of minutes every month. They can keep automatic checks on the stock of a particular item. Some of the prominent areas of computer applications are:

In Tourism: Hotels use computers to speed up billing and checkout the availability of rooms. So is the case with railways and airline reservations for booking tickets. Architects can display their scale models on a computer and study them from various angles and perspectives. Structural problems can now be solved quickly and accurately.

In Banks: Banks also have started using computers extensively. Terminals are provided in the branch and the main computer is located centrally. This enables the branches to use the central computer system for information on things such as current balance, deposits, overdrafts, interest charges, etc. MICR encoded cheques can be read and sorted out with a speed of 3000 cheques per minute by computers as compared to hours taken by manual sorting. Electronic funds transfer (EFT) allows a person to transfer funds through computer signals over wires and telephone lines making the work possible in a very short time.

In Industry: Computers are finding their greatest use in factories and industries of all kinds. They have taken over the work ranging from monotonous and risky jobs like welding to highly complex jobs such as process control. Drills, saws and entire assembly lines can be computerized. Moreover, quality control tests and the manufacturing of products, which require a lot of refinement, are done with the help of computers. Not only this, Thermal Power Plants, Oil refineries and chemical industries fully depend on computerized control systems because in such industries the lag between two major events may be just a fraction of a second.

In Transportation: Today computers have made it possible for planes to land in foggy and stormy atmosphere also. The aircraft has a variety of sensors, which measure the plane’s altitude, position, speed, height and direction. Computer use all this information to keep the plane flying in the right direction. In fact, the Auto–pilot feature has made the work of pilot much easy.

In Education: Computers have proved to be excellent teachers. They can possess the knowledge given to them by the experts and teach you with all the patience in the world. You may like to repeat a lesson hundred times, go ahead, you may get tired but the computer will keep on teaching you. Computer based instructions (CBI) and Computer Aided Learning (CAL) are common tools used for teaching. Computer based encyclopedia such as Britannica provide you enormous amount of information on anything.

In Entertainment: Computers are also great entertainers. Many computer games are available which are like the traditional games like chess, football, cricket, etc. Dungeons and dragons provide the opportunity to test your memory and ability to think. Other games like Braino and Volcano test your knowledge.

COMPUTER CLASSIFICATION

Computer Classification

Differences in certain computer characteristics have led to the development of major computer classifications based on the type of electronic signal and memory size.

Types of computers based on electronic signal

Computers, in general are of three types as per the electronic signal they transmit.

(i) Analog Computers

(ii) Digital Computers

(iii) Hybrid Computers

Analog Computers: An analog computer operates on inputs of continuously varying electrical voltages. An example of the use of an electronic analog computer is that of controlling a flight simulator for training pilots. The computer responds to the cockpit simulator control movements made by the pilot and makes physical changes in the environment so that the pilot feels as if he is controlling an actual aeroplane. Analog computers are used mainly in scientific design and production environments. Each one has to be constructed to do a specific job and will respond very quickly to changes in the measurement of inputs.

Digital Computers: In digital computers, mathematical expressions are represented as binary digits (0 and 1) and all operations are done using these digits at a very high rate. It means that the computer operates on electrical inputs that have only two states, ON and OFF. These computers are widely used in commercial and control systems. Now a days when we use the word computer, we mostly refer to a digital computer.

Hybrid Computers: Hybrid computers are computers with combined features of both digital and analog type. Desirable features of analog and digital machines can be combined to create a Hybrid Computer. This type of computer operates by counting as well as by measuring. In other words, the output can be either in the form of numbers or required units of measurement, e.g., an analog device measures patient’s heart beat (ECG). These measures will be converted into digital form and a digital device checks for any abnormality. Further, we can also input digital data like your marks and get digital results like the result of your class. Another example is a Modem. (which converts the digital signals into analog, carry it along the line and at the receiving end again changes it back into digital signal).

Types of computers based on memory size

On the basis of size of memory computers can be divided into following categories:

Microcomputer: Microcomputer is at the lowest end of the computer range in terms of speed and storage capacity. Its CPU is a microprocessor. The first microcomputers were built of 8-bit microprocessor chips. The most common microcomputer is a personal computer (PC). The PC supports a number of input and output devices. An improvement of 8-bit chip is 16-bit and 32-bit chips. Examples of microcomputer are IBM PC, PC-AT.

Mini Computer: This is designed to support more than one user at a time. It possesses large storage capacity and operates at a high speed than a microcomputer. The mini computer is used in multi-user system in which various users can work at the same time. This type of computer is generally used for processing large volume of data in an organization. They are also used as servers in Local Area Networks (LAN).

Mainframe Computer: This type of computers are generally 32-bit computers. They operate at very high speed, have very large storage capacity and can handle the workload of many users. They are generally used in centralized databases. They are also used as controlling nodes in Wide Area Network (WAN). Example of mainframes are DEC, ICL and IBM 3000 series.

Super Computer: This is the fastest and most expensive machines. It has high processing speed compared to other computers. They also have multiprocessing technique. One of the ways in which supercomputers are built is by interconnecting hundreds of microprocessors. Supercomputer is mainly used for weather forecasting, biomedical research, remote sensing, aircraft design and other areas of science and technology. Examples of supercomputers are CRAY YMP, CRAY2, NEC SX-3, CRAY XMP and PARAM from India.

FUNCTIONAL UNITS OF COMPUTER​

Functional Units of a Computer

Computer is a device that operates upon information or data. It is an electronic device which accepts input data, stores the data, does arithmetic and logic operation and outputs the information in desired format. Even though the size, shape, performance, reliability and cost of computers have been changing over the years, the basic logical structure proposed by Von Neumann has not change. The internal architecture of computers differs from one system model to another.

INPUT UNIT

Input unit accepts coded information from human operators through electromechanical devices such as the keyboard or from other computers over digital communication lines. The information received is either stored in the memory for later reference or immediately used by the Arithmetic and Logic circuitry to perform the desired operation. Finally the result is sent back to the outside through the output unit. The keyboard is wired so that whenever a key is pressed, the corresponding letter or digit is automatically translated into its corresponding code and sent directly to either the memory or the processor. Other kinds of input devices: Joy stick, track ball, mouse (pointing devices), scanner etc.

MEMORY UNIT

The memory unit stores program and data. There are two classes of memory devices– Primary memory and Secondary memory.

Primary memory (Main memory):

1. Contains a large number of semiconductor cells each capable of storing one bit of information

2. These cells are processed in group of fixed size called words containing ‘n’ bits. The main memory is organized such that the contents of one word can be stored or retrieved in one basic operation.

3. For accessing data, a distinct address is associated with each word location.

4. Data and programs must be in the primary memory for execution.

5. Number of bits in each word is called the word length and it may vary from 16 to 64 bits.

6. Fast memory

7. Expensive

8. Time required to access one word is called Memory Access Time – 10nS to 100nS. This time is fixed and independent of the location.

Secondary storage:

1. They are used when large amount of data have to be stored (also when frequent access is not necessary) E.g. Hard Disk, Compact Disk, Floppy Disk, Magnetic Tapes etc.

2. PROCESSOR UNIT

3. The heart of the computer system is the Processor unit.

4. It consists of Arithmetic and Logic Unit and Control Unit.

5. Arithmetic and Logic Unit (ALU)

6. Most computer operations (Arithmetical and logical) are executed in ALU of the processor.

7. For example: Suppose two numbers (operands) located in the main memory are to be added. These operands are brought into arithmetic unit – actual addition is carried. The result is then stored in the memory or retained in the processor itself for immediate use.

8. Note that all operands may not reside in the main memory. Processor contains a number of high speed storage elements called Registers, which may be used for temporary storage of frequently used operands. Each register can store one word of data.

9. Access times to registers are 5 to 10 times faster than access time to memory.

Control Unit

1. The operations of all the units are coordinated by the control unity (act as the nerve centre that sends control signal to other units)

2. Timing signal that governs the I/O transfers are generated by the Control Unit.

3. Synchronization signals are also generated by the Control Unit

4. By selecting, interpreting and executing the program instructions the program instructions the control unit is able to maintain order and direct the operation of the entire system.

5. The control unit and ALU’s are usually many times faster than other devices connected to a computer system. This enabled a single processor to control a number of external devices such as video terminals, magnetic taped, disk memories, sensors, displays and mechanical controllers which are much slower than the processor.

OUTPUT UNIT

1. Counter part of input unit

2. Output devices accept binary data from the computer – decodes it into original form and supplies this result to the outside world.

E.g. Printer, Video terminals (provides both input & output functions), graphic displays etc

​CHARACTERISTICS OF COMPUTER

Characteristics of a Computer

Let us identify the major characteristics of a computer. These can be discussed under the headings of speed, accuracy, diligence, versatility and memory.

1. Speed: As you know computer can work very fast. It takes only few seconds for calculations that we take hours to complete. Suppose you are asked to calculate the average monthly income of one thousand persons in your neighborhood. For this you have to add income from all sources for all persons on a day-to-day basis and find out the average for each one of them. How long will it take for you to do this? May be one day, two days or one week? Do you know your small computer can finish this work in few seconds? The weather forecasts that you see every day on TV is the result of compilation and analysis of huge amount of data on temperature, humidity, pressure, etc. from various places processed by computers. It takes few minutes for the computer to process this huge amount of data and give the result. You will be surprised to know that computer can perform several million (1,000,000) of instructions and even more per second. Therefore, we determine the speed of computer in terms of microsecond (10-6 part of a second) or nano-second (10-9 part of a second). From this you can imagine how fast your computer can perform.

2. Accuracy: Suppose some one calculates faster but commits a lot of errors in computing. Such result is useless. There is another aspect. Suppose you want to divide 15 by 7. You may work out up to 2 decimal places and say the quotient is 2.14. I may calculate up to 4 decimal places and say that the result is 2.1428. Some one else may go up to 9 decimal places and say the result is 2.142857143. Hence, in addition to speed, the computer provides very high level of accuracy or correctness in computing.

3. (c) Diligence: A computer is free from tiredness, lack of concentration, fatigue, etc. It can work for hours without creating any error. If millions of calculations are to be performed, a computer will perform every calculation with the same accuracy. Due to this capability it is better than human being in routine type of work.

4. Versatility: It means the capacity to perform completely different type of work. You may use your computer to prepare payroll slips. Next moment you may use it for inventory management or to prepare electricity bills or prepare accounts, etc. Therefore computer is highly versatile.

5. Power of Remembering: Computer has the power of storing huge amount of information or data.Information can be stored and recalled as long as you require it, for any number of years. It depends entirely upon you, how much data you want to store in a computer and when to use or retrieve these data.

6. (f) No IQ: Computer is a dumb machine and it cannot do any work without instructions from the user. It is considered as a faithful idiot that can only perform the instructions given to it at tremendous speed and with high accuracy without understanding of the work being done. Computer has to be guided as to what you want to do and in what sequence. So a computer cannot take its own decision as you can.

7. No Feeling: It does not have feelings or emotion, taste, knowledge and experience. Thus it does not get tired even after long hours of work. It does not distinguish between users.

8. Storage: The computer has an in-built memory where it can store a large amount of data. You can also store data in secondary storage devices such as floppies and CDs, which can be kept outside your computer and can be carried to other computers

COMPUTER HARDWARE​

Computer Hardware

Basic components in a computer system are central processing unit (CPU), memory, the input device and output device.

System types

We can classify systems into the following categories:

1. 8-bit, example : 8085 microprocessor

2. 16-bit, example : 8086, 286, 386 processor

3. 32-bit , example : 486

4. 64-bit, example : Pentium – II

This gives us two basic system types or classes of hardware.

1. 8-bit ( PC/XT) class systems

2. 16/32/64 (AT) class systems

PC stands for personal computers, XT stands for eXTended PC, and AT stands for an advance technology PC. The XT basically was a PC system that included a hard disk for storage in addition to the floppy drive found in the basic PC system. These systems has an 8-bit processor and an 8-bit INDUSTRY STANDARD ARCHITECTURE (ISA) bus for system expansion. Bus is the name given to expansion slots in which additional plug in circuit board can be installed. 16-bit and greater systems are said to be AT class. 16-bit (and latter 32 and 64 bit) processors and expansion slots are included. The first AT class systems had a 16-bit version of the ISA bus which is an extension of the original 8-bit ISA bus found in the PC/XT class systems. Afterwards several expansion slots were developed for AT class systems.

Example

1. 16/32 bit PS/2 microchannel architecture (MCA) bus.

2. 16-bit PC card (PCMCIA) bus

3. 16 bit ISA bus

4. 16/32 bit Extended ISA(EISA) bus

5. 32/64 – bit card Peripheral Component Interconnect (PCI) bus.

The easiest way to identify a PC/XT system is by the 8-bit ISA expansion slots regardless of the processor present in the system. AT systems can be similarly identified by having 16-bit of greater slots of any type (ISA, EISA, PCI) slots.

Motherboard

Motherboard is the important component of the computer as everything else is connected to it. And it controls everything in the system. Motherboard are available in several different shapes.Motherboard usually contain the following individual components.

1. Processor slot

2. Processor voltage regulators

3. Motherboard chipset

4. Level 2 cache

5. Memory SIMM or DIMM sockets

6. Bus slots

7. ROM BIOS

8. Clock / CMOS battery

9. Super I/O chips

Processor

The processor is often thought as the engine of the computer. Then the processor reads the commands from the memory and then executes them. the processor is one of the most expensive parts of the computers and is also one of the smallest parts.

The main component of any motherboard is the main processor chip which controls all the inner functions of the system. The CENTRAL PROCESSING UNIT(CPU) functions as the brain of every PC. It is usually inserted into the socket and is not soldered onto the motherboard as many other chips are normally done, this makes its replacement, in case of any problem, very easy. Some of the common CPU chips are:

8088,8086,80286,80386,80486, Pentium, Pentium MMX, Pentium–II, Pentium III, Pentium–IV, Intel i3 etc.

Memory

Memory is the place where computer stores the program(set of instructions telling ehe computer what to do), and data that help the program in carrying out its operations. For example, a marks sheet printing program will require students rollnumber, name and marks obtained in various subjects etc. as data. There is basically two type of memory used in a computer.

1. RAM memory

2. ROM memory

RAM memory:

RAM or random access memory is a read/write type of memory which is used by the processor to keep program, data and intermediate results during program executions. It is VOLATILE type of memory, which lose ists content when the power supply to it is switched off. The physical installation of RAM memory on the motherboard can take place in various ways.

1. DIP(dual In-line Pin) memory chips were used on initial motherboards.

2. Later SIMM ( single inline memory modules) became common.

3. Currently DIMM(dual inline memory modules) are most common memory module.

1. Bit is a binary digit that is either 0 or 1.

2. Nibble is collection of 4 bits.

3. Byte is collection of 8 bits.

4. Kilobyte is 1024 bytes

5. Megabyte is 1024 Kilobytes

6. Gigabyte is 1024 Megabytes

Read Only Memory(ROM)

ROM or Read Only Memory, as its name suggest is a read only type of memory it cannot be written. Data is written into it by the manufacturer.

1. On major advantage with the ROM is, ROM is Non-Volatile type of memory i.e it does not lose its content when the power supply to it is switched off.

2. A motherboard normally contains one or more of these ROM chips.

3. The memory capacity of a ROM varies from one type of system to another.64 KiloByte (KB) was normally sufficient for a XT system, whereas as AT system requires 256KB of ROM.

BIOS

BIOS is an abbreviation if Basic Input Output System. It is one of the most important program stored in the ROM. BIOS program lets your application program and the hardware such as floppy disk, hard disk, video adapter etc. communicate with each other.

The BIOS also contains a program called Power-On-Self-Test or POST. This post program checks the motherboard and other devices connected to the computer during the system power-on time. IBM made the original BIOS for their copyright product, but many compatible BIOS program BIOS program are available from Award, Phoenix, American Megatrends Inc. (AMI) etc. various manufacturers.

CMOS(Complementary Metal Oxide Semiconductor) Memory

In old IBM XT or compatible system, BIOS, with the help of jumpers, detected what all components are connected to the computer system.

IBM AT and higher systems do not contain these jumper switches and instead use a CMOS memory to store the system configuration, date, and time etc. information.

This CMOS memory receives power from a battery accompanying it, this battery helps it retains the information stored in it even when the system is switched off. When an AT or higher system is switched on, BIOS matches the information stored inside the CMOS with the components connected to the system and if it finds some mismatch or error, the BIOS displays some error message, explaining the problem.

There can be several programs in the system, which cannot be stored in RAM, so we need a very huge non-volatile memory, which can be used for storing all the programs, and data when the system is not in use are called as Hard disks.

CD-ROM drive

CD-ROM stands for compact disk read only memory. It consists of small disks similar to the gramophone records to hold digital information. As the name applies they are read only medium. With the advancement in technology writable CD’s are also available.

Floppy Disk Drive

Floppy disks are the slowest and the smallest form of secondary storage. They provide a simple way to carry information from one place to another, and backup small amount of files. In modern days floppy drive component is not as important as it was years ago. All PC’s made in the last 10 years use a standard 3 ½inch, 1.44 MB capacity floppy drive.

Keyboard

The keyboard is the main input device for most computers. It is used to input text or enter commands into the PC. Nowadays keyboards with additional features are available like multimedia keyboard, wireless keyboard.

Mouse

With the invention of graphical user interface mouse is used to input information into the computer. Users simply point and click to enter information. The main advantage of mouse over keyboard is simplicity. And there are many operations that are much easier to perform with a mouse then a keyboard.

Monitor

The monitor is the specialized high-resolution screen similar to a television. The video card sends the contents of its video memory to the monitor at a rate of 60 or more time per second. The actual display screen is made up or red, green and blue dots that are illuminated by electron beam from behind. The video card DAC chip controls the movement of the electron beam, which then controls what dots are turned on and how bright they are. Which then determines the picture you see on the screen.

Power supply

SMPS(Switch Mode Power Supply): The power supply supplies power to every single part in the PC. The main function of the power supply is to convert the 230 V AC into 3.3 V, 5 V and 12 V DC power that the system requires for the operations. In addition to supplying power to run the system, the power supply also ensures that the system does not run unless the power supplied is sufficient to operate the system properly. The power supply completes internal checks and tests before allowing the system to start. If the tests are successful, the power supply sends a special signal to the motherboard called Power_Good. If this signal is not present continuously, the computer does not run. Therefore, when the AC voltage dips and the power supply becomes stressed or overheated, the Power_Good signal goes down and forces a system reset or complete shutdown.

Peripheral Devices

Any external device, which is not necessary to perform the basic operation of computer, is called as peripherals. They provide additional computing capabilities. For example : Printers, Modems, Speakers etc.

Modem

Modem (Modulator and Demodulator) is typically used to send digital data over a phone line. The sending modem converts digital data into analog data, which can be transmitted over telephone lines, and the receiving modem converts the analog data back into digital form. This is used to connect to Internet. Modems are available in different capacities.

1. 300 bps – 1960s through 1983 or so

2. 1200 bps – Gained popularity in 1984 and 1985

3. 2400 bps

4. 9600 bps – First appeared in late 1990 and early 1991

5. 19.2 kilobits per second (Kbps)

6. 28.8 Kbps

7. 33.6 Kbps

8. 56 Kbps – Became the standard in 1998

9. ADSL, with theoretical maximum of up to 8 megabits per second (Mbps)

Printers

The capability to produce a printed version often called a hard copy of a document is the primary function of a printer. Different types of printers are 1) Laser 2) Inkjet 3) Dot-Matrix.

COMPUTER SOFTWARE

Computer Software

Software is generally classified into theree specific categories in the computer world:

1. System software

2. Application software

3. Utility software

1. System software: This consists of all the programmes, languages and documentation supplied by the manufacturer of the computer. This type of software is required to use the computer efficiently and conveniently. These programmes allow the application developer to write and develop their own programmes.

2. Application software: These programmes are developed by the user in order to perform some specific function for the organisation. For example, a payroll system to compute the salaries of the employees of an organisation is termed as an application software.

3. Utility software: Utility software may be considered as an application software or a system software which is very often used in the development of a programme.

Programming Language

A programming language consists of words, symbols and usage rules pertaining to the grammar that permits people to communicate with the computer. permits people to communicate with the computer. Understanding of computer software is imperfect with out a basic knowlede of programming languaes, Programming languages allow the programmers and end users to develop the programmes that are exceuted by users to develop the programmes that are executed by the computer. Many programming languages exist in the world today. Each one of the languages have their own unique vocabulary, grammar and usage. Some of these languages have been created to serve a special purpose while others are more flexible and general purpose and are suitable for many types of applications. However ingeneral, programming languages must cater to the following tasks:

1. input/ output

2. text manipulations/ calculations

3. logic/ comparison

4. storage/ retrieval

Classification of Programming Language

Machine Languages:

Machine language is the lowest form of computer language. Programmes were only written in binary based machine level language in the first generation computers. The computer understands this language only at its lowest level.

An instruction perpared in machine language has two parts:

1. Op-code: This is the first part and is the command or operation and it tells the computer what function to perform.

2. Operand: The second part of the instruction is the operand and it tells the computer where to find or store the data or instructions that are to be manipulated. The number of operands in an instrution varies from computer to computer. In a single operand machine, the binary equivalent of “ADD0481” could cause the value in a storage location 0481 to be added to a value stored in the arithmatic & logic unit. The single operand format is popular in the smallest microcomputers whereas the two operand structure is found in most other machines.

The set of instructions in a machine level language can be divided into four.

categories:

1. Arithmatic – add, subtract, multiply and divide

2. Controlled– load, store, jump instructions

3. Input output – Read and write

4. Direct use – Halt, start and end

No arithmatic or comparison operations are done in the primary memory of the computer. Instead it is done in the ALU’s special register called accumulator. Thus if we need to add two numbers, we require one instruction which will order the control unit to place a nuber in the accumulator and another instruction to identify the operation of addition.

Symbolic/ Assembly Languages:

In order to reduce the burden, symbolic languages, commonly known as assembly languages was developed in 1950’s for the second generation computers.

This language permits the use of symbols or mnemonics which are two or three letter abbreviations for the function to be performed by the instruction. These are then translated by using symbolic equivalence table. to control registers etc. However, the disadvantage of using binary has been removed.

Functions of Assembler

(i) The Assembler translates the function code into its machine code equivalent.

(ii) It assigns absolute addresses to any symbolic address or label names.

(iii) It places each instruction in central memory.

(iv) It identifies indirect addresses from direct addresses and sets the appropriate bit in the address portion of the instruction.

(v) It checks the syntax of each instruction and generates error messages.

(vi) It provides, optionally, a cross reference table between all symbolic names and their absolute addresses.

(vii) It informs the control unit to exceute the program after all errors have been corrected.

Advantages of Assembly languages

(i) They save time and reduce detail as compared to machie language.

(ii) Lesser number of errors are made and errors are easier to detect.

(iii) Assembly programs are easier to modify than machine language programs

Disadvantages of Assembly Language

(i) Writing a code is time consuming.

(ii) Assembly languages are machine dependent.

High Level Languages

The disadvantages of using assembly language brought about the development of higher level languages. Unlike the assembly programs, high level language programs may be used with little modification. High level languages are easier to learn than symbolic languages. They require less time to write, are easier to maintain, provide better documentation and 4 or 5 low- level in structions are reduced to a single high level statement.

The Operating System

The operating system is the core software component of the computer. It performs many functions and is in very basic terms an interface between your computer and the outside world. In the section about hard ware, a computer is described as consisting of several components including your monitor, keyboard, mouse and other parts. The operating system provides an interface to these parts using what is referred to as “drivers”. This is why sometimes when you install a new printer or other piece of hardware, you system will ask you to install more software called a driver.

Operating System Types

There are many types of operating systems. The most common is the Microsoft’s operating systems.

1. Windows XP Professional Edition: A version used by many businesses at workstations. It has the ability to become a member of a corporate domain.

2. Windows XP Home Edition: A lower cost version of Windows XP which is for home use only and should not be used in a business.

3. Windows 2000: A better version of the Windows NT operating system which works well both at home and as a workstation in a business. It includes technologies which allow hardware to be automatically detected and other enhancements over Windows NT.

4. Windows 2000: A better version of the Windows NT operating system which works well both at home and as a workstation at a business. It includes technologies which allow hardware to be automatically detected and other enhancements over Windows NT.

5. Windows ME: An upgraded version from windows 98 but it has been historically plagued with programming errors which may be frustrating for home users.

6. Windows 98: This was produced in two main versions. The first Windows 98 version was plagued with programming errors but the Windows 98 Second Edition which came out later was much better with many errors resolved.

7. Windows NT: A version of Windows made specifically for businesses offering better control over work station capabilities to help network administrators.

8. Windows 95: The first version of Windows after the older Windows 3.x, versions offering a better in terface and better library functions for programs.

There are other worthwhile types of operating systems not made by Microsoft. The greatest problem with these operating systems lies in the fact that not as many application programs are written for them. However if you can get the type of application programs you are looking for, one of the systems listed below may be a good choice.

1. Unix: A system that has been around for many years and it is very stable. It is primarily used as a server rather than a workstation and should not be used by anyone who does not understand the system. It can be difficult to learn, Unix must normally run on a computer made by the same company that produces the software.

2. Linux: Linux is similar to Unix in operation but it is free. It also should not be used by anyone who does not understand the system and can be difficult to learn.

3. Apple Macintosh- Most recent versions are based on Unix but it has a good graphical interface so it is both stable (does not crash often or have as many to learn). One drawback to this system is that it can only be run on Apple produced hardware.

An operating system, sometimes called an “OS”, is the main program the computer used to function properly. Operating systems act as a link between you, the user, and the programs you use on a computer. Different types of computers use different types of operating systems. The majority of computers used either run Microsoft Windows or MacOS. While files can be shared between these two types of systems. they are generally incompatible

COMPUTER INTERNET

Internet

The latest buzzword in computer world is ‘Internet’. It has taken the entire world by surprise with its cutting edge technology to connect people and computers throughout the world. Using Internet, organizations all over the world can exchange data, people can communicate with each other in a faster and effective way, and researchers can gather information in their respective areas of research. With the help of video conferencing over Internet, it has become possible that people can even see each other while communicating. Even one can do all his shopping sitting back at home. He does not bother to go to the crowded market place. Slowly shopkeepers are also opting for electronic commerce, which provides them greater reach and fastest way to do business over Internet.

SERVICES OF INTERNET—E-mail, FTP, Telnet, WWW

What does one do with the Internet? May be four things, basically: mail, discussion groups, long-distance computing, and file transfers. Internet mail is (e-mail or electronic mail), much faster as compared to normal postal mail. One can also send software and certain forms of compressed digital image as an attachment. News groups or discussion groups facilitate Internet user to join for various kinds of debate, discussion and news sharing. Programmers can maintain accounts on distant, powerful computers, execute programs. File transfer service allows Internet users to access remote machines and retrieve programs, data or text.

E-Mail (Electronic Mail)

E-mail or Electronic mail is a paperless method of sending messages, notes or letters from one person to another or even many people at the same time via Internet. E-mail is very fast compared to the normal post. E-mail messages usually take only few seconds to arrive at their destination. One can send messages anytime of the day or night and it will get delivered immediately. You need not to wait for the post office to open and you don’t have to get worried about holidays. The biggest advantage of using e-mail is that it is cheap, especially when sending messages to other states or countries and at the same time it can be delivered to a number of people around the world. It allows you to compose note, get the address of the recipient and send it. Once the mail is received and read, it can be forwarded, replied. One can even store it for later use, or delete. In a-mail even the sender can request for delivery receipt and read receipt from the recipient.

Features of E-mail:

1. One-to-one or one-to-many communications

2. Instant communications

3. Physical presence of recipient is not required

4. Most inexpensive mail services, 24-hours a day and seven days a week

5.Encourages informal communications

Components of an E-mail Address: As in the case of normal mail system, e-mail is also based upon the concept of a recipient address. The email address provides all of the information required to get a message to the recipient from anywhere in the world. Consider the e-mail ID iqbalsuccessclassescentre@gmail.com.

In the example above, “iqbalsuccessclassescentre” is the local part, which is the name of a mailbox on the destination computer, where finally the mail will be delivered. Hotmail is the mail server where the mailbox “iqbalsuccessclassescentre” exist, .com is the type of organization on net, which is hosting the mail server.

There are six main categories;

1. com Commercial institutions or organization

2. edu Educational institutions

3. gov Government site

4. mil Military site

5. net Gateways and administrative hosts

6. org Private organizations

FTP (File Transfer Protocol)

File Transfer Protocol, is an Internet utility software used to upload and download files. It gives access to directories or folders on remote computers and allows software, data and text files to be transferred between different kinds of computers. FTP works on the basis of same principle as that of Client/Server. FTP “Client” is a program running on the your computer that enables you to talk to, and get stuff from, remote computers. The FTP client takes FTP commands and send them as requests for information from the remote computer or known as FTP servers. To access remote FTP server it is required but not necessary to have an account in the FTP server. When the FTP client gets connected, FTP server asks for the identification in-terms of User Login name and password of the FTP client. If one does not have an account in the remote FTP server, still he can connect to the server using anonymous login. Using anonymous login anyone can login in to a FTP server and can access public file archives, anywhere in the world, without having an account. One can easily Login to the FTP site with the username anonymous and e-mail address as password. The basic objectives of FTP are:

1. to give flexibility and promote sharing of computer programs, files and data

2. to transfer data reliably and more efficiently over network

3. to encourage implicit or indirect use of remote computers using Internet

4. to shield a user from variations in file storage systems among hosts.

5. The basic steps in an FTP session are:

6. Start up your FTP client, by typing ftp on your system’s command line/’C>’ prompt (or, if you are in a Windows, doubleclick on the FTP icon)

7. Give the FTP client an address to connect to. This is the FTP server address to which the FTP client will get connected

8. Identify yourself to the FTP remote site by giving the Login Name

9. Give the remote site a password

10. Remote site will verify the Login Name/Password to allow the FTP client to access its files

11. Look directory for files in FTP server

12. Change Directories if required

13. Set the transfer mode (optional);

14. Get the file(s) you want, and

15. Quit.

Telnet (Remote Computing)

Telnet or remote computing is telecommunication utility software, which uses available telecommunication facility and allows you to become a user on a remote computer. Once you gain access to the remote computer, you can use it for the intended purpose. The TELNET works in a very step by step procedure. The commands typed on the client computer are sent to the local Internet Service Provider (ISP), and then from the ISP to the remote computer that you have gained access. Most of the ISP provides facility to TELENET into your own account from another city and check your e-mail while you are traveling or away on business.

WORLD WIDE WEB (WWW)

WWW is the acronym for the World Wide Web. It is also commonly known as ‘The Web’. The WWW is hypertext based information retrieval tool. One can easily surf the Web by jumping from one document to another using the links in those documents. These documents can be in many formats, such as text, graphics, animation, sound and latest is video. They may also be a combination of all these. All the information on Internet are presented to the user as a document or more popularly known as Web Page. All these Web Pages are link to each other or even to section within a Web Page. And these links are known as Hyper Links. The tool used to view these Web Pages on Internet is known as Internet browser or simply browser. It is a software program specifically developed to extract information on user request from the Internet and pesent them as a Web Page to the viewer.The process of using browser to view information on Internet is known as Browsing or Surfing.

Internet Address

Just like every house, every office, every location has an address, every page on the Internet has a unique address. This address is used to get the web page for user from Internet. Just as the address of a house or office is known as its postal address, the address on the Internet is known as URL (Uniform Resource Locator). A typical Internet address or URL would look like;

http//www.iqbalsuccessclassescentre.blgspot.com/computers/internet/url.htm

The URL locates a particular web Page, among all the computers connected to the Internet. The URL contains the components that specify the protocol, server, and pathname of an item. Let us examine the URL given above (http//www.iqbalsuccessclassescentre.blogspot.com/computers/internet/url.htm).

The protocol is followed by a colon (http:), the server is preceded by two slashes (//www.iqbalsuccessclassescentre.blogspot.com), and each segment of the pathname is preceded by a single slash (/computers/internet/url.htm). A protocol is set of rules that tells the computer know how to interpret the information at that address.The first component, the protocol, defines the manner for interpreting computer information. Many Internet pages use HTTP (HyperText Transfer Protocol). Other common Internet protocols that one might come across are FTP (File Transfer Protocol), NEWS (Usenet news groups protocol), and GOPHER (an alternative transfer protocol). Gopher protocol is mostly out of date now. Some examples are:

1. http://-Used to access HTML documents, or web pages.

2. gopher://-Used to connect to a gopher menu of access gopher documents.

3. ftp://-Used to connect to an FTP site or download a particular file via FTP.

4. telnet://-Used to connect to a remote Internet site using Telnet.

The second component, the server identifies the computer system that stores the information you seek and is always preceded by two slashes. A server is a computer that has information stored on it and sends it to the client, when a request is made. Each server on the Internet has a unique address name whose text refers to the organization maintaining the server. The last component (/computers/internet/), defines the path within the Server where the requested item (url.htm) will be found. Most of the Web page will have.htm or .html as their secondary or extension name.

How to get connected to Internet: There are various type of connectivity to get hook on to Internet. They all can be broadly classified into following category.

(i) Gateway Access: Gateway Access is also known as Level-One connection. It is the access to the Internet from a network, which is not on the Internet. The gateway allows the two different types of networks to “talk” to each other. But the users of the Gateway Internet have limited access to the Internet. They might not be able to use all the tools available on Internet. The local Internet Service Provider(ISP) normally defines this limitation. Good example of network with Level One connectivity within India is that of VSNL (Videsh Sanchar Nigam Limited). All access to Internet from India are through VSNL gateway.

(ii) Dial-up Connection: ‘Dial-up’ connection is also known as Level Two connection. This provides connection to Internet through a dial-up terminal connection. The computer, which provides Internet access is known as ‘Host’ and the computer that receives the access, is ‘Client’ or ‘Terminal’. The client computer uses modem to access a “host” and acts as if it is a terminal directly connected to that host. 56K modem access is now widely available and supported by most ISPs. It allows user to surf the Web at 56 Kbps with graphics. So this type of connection is also known as ‘Remote Modem Access’ connection. And the host to which the client gets connected is actually connected to the Internet by a full time connection. In dial-up connection to Internet, Host carries all the command that are typed on a client machine and forward them to Internet. It also receives the data or information from the Internet on behalf of the ‘Client’ and passes it to them. The client computer acts as a ‘dumb’ terminal connected to remote host. This type of connection can further be divided into three categories.

1. Shell Connection: In this type of Internet Connection, the user will get only textual matter of a Web Page. This connection does not support Graphics display. However the user will be able to surf the Internet, do FTP, receive mail. Shell Accounts were the only type of Internet access available for many years before the Internet entered in to the world of graphics and became more users friendly.

2. TCP/IP Connection: Today’s graphical World Wide Web browsers provide easier access with multimedia sound and pictures. The major difference between Shell and TCP/IP account is that, Shell account can only display text and does not support graphics display, whereas TCP/IP can display both. Hence it is more popular Internet connection. Shell accounts are slowly phasing out from the Internet scenario.

3. ISDN: ISDN (Integrated Services Digital Network) offers Internet connectivity at speeds of up to 128 Kbps through the use of digital phone lines. ISDN is a dial-up service that has been provided by telephone companies for many years. This line combines two 64 Kbps channels to offer 128 Kbps band width broken into three bands: one band for the ringing signal of your phone, one band for your telephone conversation, and one band for data. To use ISDN, you will need a serial communications port, an ISDN modem, and ISDN telephone line from telephone company operating in your areas.

To access any of these dial-up accounts you need the followings:

1. Computer

2. Modem

3. Telephone Connection

4. Shell or TCP/IP/ISDN account from the ISP

5. Internet client software such as Internet browser

(iii) Leased Connection: Leased connection is also known as direct Internet access or Level Three connection. It is the secure, dedicated and most expensive, level of Internet connection. With leased connection, your computer is dedicatedly and directly connected to the Internet using highspeed transmission lines. It is on-line twenty-four hours a day, seven days a week. Leased Internet connections are limited to large corporations and universities who could afford the cost.

(iv) DSL: Digital Subscriber Line (DSL) is the newest technology being used for Internet access. DSL connects your home or office to the Internet through the same telephone wire that comes from the telephone pole on the street. Like ISDN, with DSL, user can make and receive telephone calls while connected simultaneously to the Internet. However, DSL service is limited in the distance that you can be from the provider’s point of presence (POP). To use DSL you will need a DSL modem (also called a router), a Network Interface Card (NIC), and a telephone line. DSL is also relatively new technology that is just being introduced in many places. Hardware developers are working with service providers to make the service cost affordable for consumers. As time goes by, the service should become more widely available at a reasonable price.

(v) Cable Modem Connection: The connection speed can be up to 10 times that of a dial-up and the cost is about twice that of an ISP’s dial-up account, with no phone company charges. Many people who have cable TV can now get a high – speed connection to the internet from their cable provider. Cable lines offer an extremely high bandwidth connection to the Internet. It divides the connection into lots of bands, and translates the data in the bands into signals that can be carried through cable lines. Cable modems change these signals into IP packets that your computer can understand. To use cable modems you will need a cable splitter, a cable modem, and the service from a cable company. The installation process can be complex and is better left to a professional.

SEARCHING ON THE WEB

One of the most common problems all Internet users face is the fact that it can be quite difficult to find what you want on the Internet. There is no central “main menu” that users can access to navigate through the Internet. Although there might not be an official menu, there are several resources available – both on-line and off-line – that can make “surfing the net” easier. The Internet is a terrific resource. It contains hundreds of web sites dedicated to thousands of topics. There are some web sites, which are used to search information on the web. There are more than 2,500 search services presently on the Web. Search services on the Internet come in two main flavours:

search engine that index words or terms in Internet documents; and directories that classify Web documents or locations into an arbitrary subject classification scheme or taxonomy.

Most search engines take one or more words entered by the user, search the contents of every Web page stored in their databases and display the result. Search engines tend to “index” (record by word) all of the terms on a given Web document. Or they may index all of the terms within the first few sentences, the Web site title, or the document’s metatags. Internet directories are on-line Web sites that place Web page into one or more categories. Web pages are usually listed with a brief description and their URL. Depending on the Internet directory you are using, a search engine may also be available, as well as a Random URL link. Directories operate on a different principle. They require people to view the individual Website and determine its placement into a subject classification scheme or taxonomy. Some popular search engineers are:

1. Google- http://www.google.com

2. Bing – http://www.bing.com

3. Yahoo! – http://www.yahoo.com

Your ability to find the information you seek on the Internet is a function of how precise your queries are and how effectively you use search services. Poor queries return poor results; good queries return great results.

POINTS TO REMEMBER ABOUT COMPUTER

Points to Remember

1. A computer is a data processing machine having two main parts: Hardware and Software.

2. Hardware comprises of the physical units of a computer system while software is a set of programs.

3. Hardware and software together make a computer system functional.

4. Data are raw facts and figures.

5. An operating system is an interface between the user and the computer hardware and it manages computer resources.

6. An operating system performs different functions and is responsible for process management, file management, etc.

7. There are many kind of operating system. Some popular names are:- DOS, UNIX, Windows, Linux, Mac OS, etc.

8. The Windows Explorer program is more efficient for viewing folders in Windows.

9. Windows Explorer is divided vertically into two parts of two panes. The left side pane displays disk drives and folders in a hierarchical order.while the right pane displays the content of the folder / drive that is selected on left side pane.

10. The process of linking text values in a series within a formula is called ‘concatenation’.

11. A computer is a data processing machine.Data processing involves some activities like data capturing, data manipulation and information management.

12. Collection of interrelated data is called a database.

13. Computers are very useful for maintaining databases.

14. A relational database is a collection of data items arranged as a set of formally described tables from which data can be accessed or reassembled in many different ways without having reorganize the database tables.

15. MS Access is a powerful program to create and manage our databases.

16. Collection of data about a specific topic is called a table.

17. A form is a graphical representation of a table.

18. A report is a Presentation of data in a printed form.

19. We can create mailing labels for your database using MS Access.

20. Internet is the network of computer networks with million of computers attached to it.

21. Website are files in servers, which are powerful computers.

22. Website contain pages to be known as Web Pages.

23. The collection of all websites is known as World Wide Web (WWW).

24. Ted Nelson, in 1960s, first coined the term ‘Hyper Text’

25. Html is a markup language.

26. HTML is used to create Web Pages. It uses commands to be known as Tags.

27. To compose HTML documents, text editors are used. HTML documents are viewed in Web browser.

28. The tools are grouped by type in the Photoshop toolbox.

29. Some of the tool icons have a tiny black triangle in the lower-right corner of their icons. This means that there are more tools of the same general kind available on a pop up-menu.

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