The study of this unit will highlight the characteristics and evolution of computers. It will also help you to understand the basic terminology associated with computers. After studying this unit, you should be able to ; ; ; ; ; ; ; ; ; understand the basic characteristics of computers, understand how the computers evolved, understand the components that make up a computer, differentiate between hardware and software, differentiate between system and application software, understand the difference between bits and bytes, classify devices as input and output devices, differentiate between ROOM and RAM. D appreciate the use of various secondary storage devices. 1 . 2 WHY COMPUTER? The word 'Computer' literally means to 'Compute' or to 'Calculate. Stated simply, it is an electronic device, which processes Information based on the instructions provided, to generate the desired output. It, therefore, requires two 5 This can schematically be shown in Figure 1. 1 . Data Process Instructions Input Output Figure 1. 1 : Processing Information Data can be of any type - text, numeric, alpha-numeric, image, picture, sound etc. The instructions that act upon this data are also called the program or software in computer terminology. 2. 1 Characteristics of Computers The characteristics of computers that have made them so powerful and universally useful are speed, accuracy, diligence, versatility and storage capacity : Speed Computers work at an incredible speed. The speed with which it performs is way beyond human capabilities. As a comparison, it can do in one minute what a human being would probably take a lifetime! When we refer to the speed of computers, we have to talk in terms of milliseconds (hundredth of a second), microseconds (millionth of a second), nanoseconds (billionth of a second), and even picoseconds (trillionth of second).

A powerful computer is capable of performing about 3-4 million simple instructions per second. Accuracy In addition to being fast, computers are also accurate. Errors that may occur can almost always be attributed to human error (inaccurate data, poorly designed system or faulty instructions/programs written by the programmer) rather than technological weaknesses. In fact, a special term GIG (Garbage in Garbage Out) has been coined to represent a scenario where faulty results are got due to inaccurate instructions or faulty data.

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Diligence Unlike human beings, computers are highly consistent. They do not suffer from human traits of boredom and tiredness resulting in lack of concentration. Computers, therefore, score high over human beings in performing voluminous and repetitive Jobs. Versatility Computers are versatile machines and are capable of performing any task as long as it can be broken down into a series of logical steps. This means that their capability is, once again, limited only by human intelligence.

As is evident, in today's fast developing technology-world, it is almost inconceivable to find an area where computers are not being used. The presence of computers can be seen in every peer - Railway / Air reservation, Banks, Hotels, Weather forecasting, and many more. 6 Storage Capacity Today's computers can store volumes of data. Unlike human memory where unimportant information is relegated to the back of the mind and forgotten as time progresses, a piece of information once recorded (or stored) in the computer, can never be forgotten and can be retrieved almost instantaneously!

Information can, therefore, be retained as long as desired (using secondary storage - a type of detachable memory). SAA 1 Identify the characteristics of a computer that have contributed towards making it such a popular device. 1. 3 EVOLUTION OF COMPUTERS The history of computers can be traced back to almost 2000 years ago, with the advent of abacus, a wooden rack holding two horizontal wires with beads strung on them. Numbers are represented using the position of beads on the rack. Fast and simple calculations can be carried out by appropriately placing the beads.

In 1620, an English mathematician by the name William Oughtn't invented the slide rule - a calculating device based on the principle of logarithms. It consisted of two graduated scales devised in such a manner that suitable alignment of one scale against the there, made it possible to perform additions, compute products etc. Just by inspection. Figure 1. 2 : The Abacus Blaine Pascal, a French mathematician, is usually credited for building the first digital computer in 1642. He invented the mechanical calculating machine. Numbers were entered in this machine by dialing a series of numbered wheels.

Another series of toothed wheels transferred the movements to a dial, which showed the results. In 1671, Gottfried von Leibniz, a German mathematician, invented a calculating machine which was able to add and perform multiplications. He invented a 7 special stepped gear mechanism for introducing the addend digits, which is still being used. The prototypes made by Pascal and Leibniz were not used in many places. It was only about a century later that Thomas of Collar created the first successful mechanical calculator which could add, subtract, multiply, and divide.

A lot of improved desktop calculators by various inventors, followed, such that by 1890 a range of improvements like accumulation of partial results, storage of past results, and printing of results, were not uncommon. 1. 3. 1 The First Computer Charles Babbage, a professor of mathematics at Cambridge University, England, realized that many long calculations usually consisted of a series of actions that were constantly repeated and hence could possibly be automated. By 1822, he designed an automatic calculating machine that he called the 'Difference Engine'.

It was intended to be steam powered and fully automatic (including printing of result tables), commanded by a fixed instruction program. In short, he developed a prototype of a computer which was 100 years ahead of time and is, therefore, considered as the father of modern day computers. A step towards automated by Herman Hollering, who worked in the US Census Bureau in 1890. He along with James Powers developed devices that could read information that had been punched into cards, without any human help.

This resulted in reducing reading errors, increased workflow, and make availability of unlimited memory (punched cards could be used as easily accessible memory of unlimited size). These advantages were seen by various commercial companies and soon led to the development of improved punch-card using computers by companies like International Business Machines (MOM), and Remington. . 3. 2 Some Well Known Early Computers Mark I After World War II there was a need felt for advanced calculations. By that time, many reliable mechanical desk calculators had been developed. Howard A.

Keen of Harvard University, while working on his doctorate in physics, in the year 1937, designed a machine that could automatically perform a sequence of arithmetic operations. He completed this in 1944 and named it as Mark l. This machine performed a multiplication and division at an average of about four and eleven seconds respectively. The results were printed at a rate of one result per five seconds. MANIAC The World War II also produced a large need for computer capacity especially for the military. New weapons were made for which trajectory tables and other essential data were needed.

In 1942, Professors John P. Checker and John W. Macaulay at the Moore School of Engineering of the University of Pennsylvania, USA decoded to build a high speed computer to do the Job. This was called the MANIAC (Electronic Numeric Integrator and Calculator). 8 It used 18,000 vacuum tubes, about 1,800 square feet of floor space, and consumed about 180,000 watts of electrical power. It had punched cards 1/0 and its programs were wired on boards. MANIAC is accepted as the first successful high-speed electronic digital computer which was used from 1946 to 1955.

DIVIDE Fascinated by the success of MANIAC, John Von Neumann, a mathematician, undertook an abstract study of computation in 1945. In this he aimed to show that a computer should be able to execute any kind of computation by means of a proper programmed control. His ideas, referred to as 'stored program technique', further became essential for future generations of high-speed digital computers and were universally accepted. The Asia idea behind the stored program concept was that data as well as instructions can be stored in the computer's memory to enable automatic flow of operations.

Between 1947 and 1950, the More School personnel and the Ballistics Research Laboratory of the US army built a computer named ADVANCE (Electronic Discrete Variable Automatic Computer), which was based on Von Newsman's concept of stored program. UNIVAC The Universal Automatic Computer (UNIVAC), developed in 1951, was the first digital computer to be produced and was installed in the Census Bureau. The first-generation stored-program computers needed a lot of maintenance, cached 70% to 80% reliability of operations and were used for almost 10 years. Available computers. . 3. 3 Computer Generations 'Generation' in computer terminology is a 'step' ahead in technology. As you go through the history of evolution of computers, you will find that the earliest computers were big in size, consumed a lot of power, and heated up quickly, due to which it had to be shut down frequently - to be cooled. It were very cumbersome and expensive to build and maintain. As technology improved, computers became compact, extra storage space, faster and more powerful. From a user's perspective, they become user friendly and more affordable.

This has largely contributed towards the popularity that computers have gained today. The term 'generation' was earlier used only to distinguish between varying hardware technologies but was later extended to include both hardware and software. A comparison of generations is made below: First Generation Computers (1940 to 1956) The first generation of computers were characterized as vacuum tubes in the circuitry and magnetic drums for memory. These computers were enormous in size, used great deal of electricity ND were expensive to operate. It also had limited storage capacity. 9 Figure 1. : Vacuum Tube First generation computers relied on machine language (binary-coded program) to perform operations and could solve only one problem at a time. Punched cards and paper tapes were used to input data and instructions, and output was displayed on printouts. Early computers like MANIAC, ADVANCE, and UNIVAC can be classified as first generation computers. Second Generation Computers (1956 to 1963) In the early sass, the discoveries of Transistor and Magnetic core memory changed the image of amputees - from unreliable to highly reliable machines with increased capability, and higher storage capacity. Figure 1. : First Silicon Transistor The transistor was far superior to vacuum tube, allowing computers to become smaller in size, cheaper, reliable, and more energy efficient. Though transistor still generated a great deal of heat, it was a substantial improvement over the vacuum tube. Second generation of computers were also characterized by allowing programmers to specify instructions in symbolic (or assembly) language rather than cryptic binary machine language. High level programming languages like COBOL (Common Business Oriented Language) and FORTRAN (FORmula TRANslation) were programming, these machines were expensive to purchase and operate.

Such computers were, therefore, mostly found in large computer centers or government/ private laboratories with many programmers and support professionals. 10 Third Generation Computers (1964 to 1971) The development of Integrated Circuit by Jack Silky, an engineer with Texas Instruments, in 1958, was the hallmark of the third generation of computers. Punched cards and printouts gave way to devices like boards and monitors making it easier for the user to interact with the computer.

Computer manufacturers could provide a range of accessories like the cathode ray tube display devices, page printers, consoles etc. Existence of an operating system allowed the device to run various applications at one time with the central program monitoring the memory. For the first time, computers were being widely used in business for areas like . ; ; ; ; Accounting Payroll Billing ; Tracking Inventory, etc. This generation of computers were characterized by substantially smaller and cheaper than its predecessors. Figure 1. : Chips Fourth Generation Computers (1971 to present) The trend in sass was to move from single-purpose but powerful computers towards cheaper computer systems that could support a large range of applications. A new revolution in computer hardware came into existence which could shrink the computer logic circuitry and its components using the Large Scale Integration (LSI) technology. Hundreds of components could now fit onto a single chip! Figure 1. 6 : Intel Pentium Microprocessor Chip 11 In the sass, very large scale integration (VEILS) squeezed hundreds of thousands of components onto a single chip.

This shrinking trend continued and led to the introduction of personal computers (PC's) - programmable machines that are small enough and inexpensive so that these can be purchased and used by individuals. Companies like Apple Computers, and IBM introduced very successful PC's. The ICC technology was not only used to construct the processor, but also for the construction of memory. The first memory chip was constructed in 1970 and could hold 256 bits. Fifth Generation Computers (the Road Ahead) The fifth generation of computers characterized by artificial intelligence is in the process of development.

The goal here s to develop a devices that are capable of learning and responding to natural large scale integration, along with new programming languages and will be capable of having amazing whereabouts, in the area of artificial intelligence, such as voice recognition. SAA 2 What unique features classify computers into different generations? 1. 4 COMPONENTS OF A COMPUTER The computer system essentially comprises into three important parts - input device, central processing unit (CAP]), and the output device. The CPU itself is made of three components namely, the arithmetic logic unit (ALL]), memory unit, and the control nit.

In addition to these, auxiliary storage/secondary storage devices are used to store data and instructions on a long-term basis. Central Processing Unit Arithmetic Logic Unit Input Unit Main Memory Control Unit Output Unit Secondary Storage Figure 1. 7 : Schematic Representation of a Computer 12 Input Unit Data and instructions must be entered into the computer system for processing, and results obtained from computations must be displayed or recorded for the user. The input device serves the purpose of receiving data and instructions in a form that can be understood by the computer.

Central Processing Unit Data and instructions (programs) are stored in the computer's memory after which all the major calculations and computations are carried out within the CAP]. The CPU is also responsible for controlling the operations of various units of the computer system. Arithmetic Logic Unit (ALL') All calculations and comparisons, based on the instructions provided, are carried out within the ALL]. It performs arithmetic functions like add, subtract, multiply, divide and logical operations like greater than, less than, and equal too. Main Memory The main memory holds data and instructions after input, till they are needed.

It also holds the processed results that are awaiting output. Control The function of the control unit is to execute the instructions of a program, one by one, in the desired sequence. It interprets each instruction and then prompts its execution by one of the units like input, output, ALL], storage. For example, a comparison of two numbers (a logical operation) to be performed by the ALL may require loading the two numbers into the main memory which is a function performed by the control unit. It then will pass on the execution of the 'compare' unction to the ALL].

Output Unit The processed data, stored in the memory of the computer is sent to the output unit, which then converts it into a form that can be the display device, or on paper (hard copy). Secondary Storage Also termed as 'auxiliary or 'backup' storage, is typically used as a supplement to main storage. It is much cheaper than the main storage and stores large amount of data and instructions permanently. Hardware devices like magnetic tapes and disks fall under this category. SAA 3 What are the basic components of a computer system? 13 1. 5 HARDWARE vs. SOFTWARE

The electrical, electronic, mechanical, and magnetic components that make up the computer system are together termed as 'hardware'. These include components that are responsible for user input, display, and mathematical processing. The CAP], disk drives, internal chips and wiring, modem, peripheral devices like the monitor, keyboard, mouse, printer, speakers etc. Are together termed as computer hardware. Computer hardware cannot perform any manipulation or calculation without being instructed as to what to do and how to do it. Programs (or instructions) are required to tell the computer what to do.

The generic term for computer programs is 'software'. Software comes in two main types - system software and application software. 1. 6 SYSTEM vs. APPLICATIONS SOFTWARE System software consists of programs that control the operations of the computer system itself. It consists of a group of programs that control the operations of a computer equipment including functions like managing memory, managing peripherals, loading, storing, and is an interface between the application programs and the computer. MS DOS (Microsoft's Disk Operating System), UNIX are examples of system software.

Software that can perform a specific task for the user, such as word processing, accounting, budgeting or payroll, fall under the category of application software. Such programs run on top of an operating system (like Windows, UNIX, Linux, Macintosh) and are used to carry out specific functions. Word processors, spreadsheets, database management systems are all examples of general purpose application software. 1. 7 BITS AND BYTES All information in the computer is handled using electrical components like the integrated circuits, semiconductors, all of which can recognize only two states - resonance or absence of an electrical signal.

Two symbols used to represent these two represents the absence of a signal, 1 represents the presence of a signal. A BIT is, therefore, the smallest unit of data in a computer and can either store a O or 1 . Since a single bit can store only one of the two values, there can possibly be only four unique combinations: 0001 10 11 Bits are, therefore, combined together into larger units in order to hold greater range of values. BYTES are typically a sequence of eight bits put together to create a single computer alphabetical or numerical character.

More often referred to in larger multiples, bytes may appear as Kilobytes (1 ,024 bytes), Megabytes (1 ,048,576 bytes), Gestates (1 ,824), -reiterates (proxy. 1 bytes), or patents (proxy. Bytes). 14 Bytes are used to quantify the amount of data digitally stored (on disks, tapes) or transmitted (over the internet), and are also used to measure the memory and document size. SAA 4 State TRUE or FALSE (a) (b) All code or data is stored and processed in computers using two symbols - O and 1 . A 'Byte' is a group of four bits and is often used to store characters. 1. 8 INPUT AND OUTPUT DEVICES

The computer will be of no use unless it is able to communicate with the outside world. Input/output devices are required for users to communicate with the computer. In simple terms - input devices bring information INTO the computer and output devices bring information OUT of a computer system. These input/output devices are also known as peripherals since they surround the CPU and memory of a computer system. Some commonly used Input/output devices are listed in a table below. Input Devices Keyboard Mouse Joystick Scanner Light Pen Touch Screen Output Devices Monitor LCD Printer Plotter

Input Devices Keyboard It is a text base input device that allows the user to input alphabets, numbers and other characters. It consists of a set of keys mounted on a board. Alphanumeric Keypad/ Special-function Keys Function Keys Cursor Movement Keys Numeric Keypad Figure 1. 8 : Qwerty Keyboard Layout 15 Alphanumeric Keypad : It consists of keys for English alphabets, O to 9 numbers, and special characters like + - / * ( ) etc. Function Keys : There are twelve function keys labeled Fl, 8, , Fl 2. The functions assigned to these keys differ from one software package to another. These keys are also user programmable keys.

Special- function Keys : These keys have special functions assigned to them and can be used only for those specific purposes. Functions of some of the important keys are defined below. Is used similar to the 'return' key of the typewriter and is used to execute a command or program. Enter Spacer Is used to enter a space at the current cursor location. Backspace Is used to move the cursor one position to the left and also delete the character in that position. Delete Is used to delete the character at the cursor position. Insert Is used to toggle teen insert and overwrite mode during data entry.

Shift Is used to type capital letters when pressed along with an alphabet key. Also used to type the special characters located on the upper-side of a key that has two characters defined on the same key. Caps Lock Is used to toggle between the capital lock feature. When 'on' locks the alphanumeric keypad for capital letters input only. Tab Is used to move the cursor to the next tab position defined in the document. Used to insert indentation into a document. CTR Or the control key is used in conjunction with other keys to provide additional functionality on the keyboard.

Alt Also like the control key, is always used in combination with other keys to perform specific tasks. Sec Usually used to negate a command. Also used to cancel or abort executing programs. Numeric Keypad Is located on the right side of the keyboard and consists of keys having numbers (O to 9) and mathematical operators (+ - * I) defined 16 on them. This keypad is provided to support quick entry for numeric data. Cursor Movement Keys Are have arrow keys used to move the cursor in the direction indicated by the arrow (up, down, left, right).