Introduction to Computers

introduction To Computers INTRODUCTION TO COMPUTERS 1.1 INTRODUCTION A computer is a programmable machine designed to perform arithmetic and logical operations automatically and sequentially on the input given by the user and gives the desired output after processing. Computer components are divided into two major categories namely hardware and software. Hardware is the machine itself and its connected devices such as monitor, keyboard, mouse etc. Software are the set of programs that make use of hardware for performing various functions. Generally, the term is used to describe a collection of devices that function together as a system. It performs the following three operations in sequence. 1. It receives data & instructions from the input device. 2. Processes the data as per instructions. 3. Provides the result (output) in a desired form. Data : It is the collection of raw facts, figures & symbols. Ex : Names of students and their marks in different subjects listed in random order. Information : It is the data that is processed & presented in an organized manner. Ex : When the names of students are arranged in alphabetical order, total and average marks are calculated & presented in a tabular form, it is information. Program : Set of instructions that enables a computer to perform a given task. 1.2 OBJECTIVES After going through this lesson you would be able to: Familiarise yourself with characteristics of computers Identify the basic components of a computer Explain the importance of various units of a computer Differentiate between system software and application software Differentiate between a hardware and a software Explain the importance of operating system Computer generations 1 1/12 introduction To Computers 1.3 CHARACTERISTICS OF COMPUTERS The characteristics of computers that have made them so powerful and universally useful are speed, accuracy, diligence, versatility and storage capacity. Let us discuss them briefly. Speed Computers work at an incredible speed. 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) 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, are better than 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. The presence of computers can be seen in almost every sphere – Railway/Air reservation, Banks, Hotels, Weather forecasting and many more. Storage Capacity Today’s computers can store large volumes of data. A piece of information once recorded (or stored) in the computer, can never be forgotten and can be retrieved almost instantaneously. Cost effectiveness : Computers reduce the amount of paper work and human effort, thereby reducing costs. Automation : Computers can be instructed to perform complex tasks automatically ( which increases the productivity). Limitations of computers : 1. Computers need clear & complete instructions to perform a task accurately. If the instructions are not clear & complete, the computer will not produce the required result. 2. Computers cannot think. 3. Computers cannot learn by experience. 1.4 COMPUTER ORGANIZATION A computer system (fig.1.1) consists of mainly four basic units; namely input unit, storage unit, central processing unit and output unit. Central Processing unit further includes Arithmetic logic unit and control unit, as shown in Figure 1.2. 2 2/12 introduction To Computers A computer performs five major operations or functions irrespective of its size and make. These are it accepts data or instructions as input, it stores data and instruction it processes data as per the instructions, it controls all operations inside a computer, and it gives results in the form of output. 1.4.1 Functional Units: a. Input Unit: This unit is used for entering data and programs into the computer system by the user for processing. ANATOMY OF COMPUTERS The computer system consists of three units: 1. Input device 2. Central Processing Unit (CPU) 3. Output device b. Storage Unit: The storage unit is used for storing data and instructions before and after processing. 3 3/12 introduction To Computers c. Output Unit: The output unit is used for storing the result as output produced by the computer after processing. d. Processing: The task of performing operations like arithmetic and logical operations is called processing. The Central Processing Unit (CPU) takes data and instructions from the storage unit and makes all sorts of calculations based on the instructions given and the type of data provided. It is then sent back to the storage unit. CPU includes Arithmetic logic unit (ALU) and control unit (CU) Arithmetic Logic Unit: All calculations and comparisons, based on the instructions provided, are carried out within the ALU. It performs arithmetic functions like addition, subtraction, multiplication, division and also logical operations like greater than, less than and equal to etc. Control Unit: Controlling of all operations like input, processing and output are performed by control unit. It takes care of step by step processing of all operations inside the computer. 1.4.2 Memory Computer’s memory can be classified into two types; primary memory and secondary memory a. Primary Memory can be further classified as RAM and ROM. RAM or Random Access Memory is the unit in a computer system. It is the place in a computer where the operating system, application programs and the data in current use are kept temporarily so that they can be accessed by the computer’s processor. It is said to be ‘volatile’ since its contents are accessible only as long as the computer is on. The contents of RAM are no more available once the computer is turned off. ROM or Read Only Memory is a special type of memory which can only be read and contents of which are not lost even when the computer is switched off. It typically contains manufacturer’s instructions. Among other things, ROM also stores an initial program called the ‘bootstrap loader’ whose function is to start the operation of computer system once the power is turned on. b. Secondary Memory RAM is volatile memory having a limited storage capacity. Secondary/auxiliary memory is storage other than the RAM. These include devices that are peripheral and are connected and controlled by the computer to enable permanent storage of programs and data. Secondary storage devices are of two types; magnetic and optical. Magnetic devices include hard disks and optical storage devices are CDs, DVDs, Pen drive, Zip drive etc. Hard Disk Hard disks are made up of rigid material and are usually a stack of metal disks sealed in a box. The hard disk and the hard disk drive exist together as a unit and is a permanent part of the computer where data and programs are saved. These disks have storage capacities ranging from 1GB to 80 GB and more. Hard disks are rewritable. Compact Disk Compact Disk (CD) is portable disk having data storage capacity between 650-700 MB. It can hold large amount of information such as music, full-motion videos, and text etc. CDs can be either read only or read write type. 4 4/12 introduction To Computers Digital Video Disk Digital Video Disk (DVD) is similar to a CD but has larger storage capacity and enormous clarity. Depending upon the disk type it can store several Gigabytes of data. DVDs are primarily used to store music or movies and can be played back on your television or the computer too. These are not rewritable Flash Drive: It is a small, portable device that can be used to store, access and transfer data. Due to its small size, it is commonly called Pen drive. It is also called USB drive. We can read, write, copy, delete, and move data from computer to pen drive or pen drive to computer. It comes in various storage capacities of 2GB, 4GB, 8GB etc. It is popular because it is easy to use and small enough to be carried in a pocket. This device is plugged into the USB port of the computer and the computer automatically detects this device. Input / Output Devices: These devices are used to enter information a) Input Devices An input device is any device that provides input to a computer. There are many input devices, but the two most common ones are a keyboard and mouse. Every key you press on the keyboard and every movement or click you make with the mouse sends a specific input signal to the computer. Keyboard: The keyboard is very much like a standard typewriter keyboard with a few additional keys. The basic QWERTY layout of characters is maintained to make it easy to use the system. The additional keys are included to perform certain special functions. These are known as function keys that vary in number from keyboard to keyboard. There are different types of keys on the keyboard. The keys are categorized as : Alphanumeric keys , including letters & numbers. Punctuation keys, such as colon (:), semicolon (;) Question mark (?), Single & double quotes (‗,‖) Special keys such as arrow keys, control keys, function keys (F1 to F12), HOME, END etc Mouse: A device that controls the movement of the cursor or pointer on a display screen. A mouse is a small object you can roll along a hard and flat surface (Fig. 1.5). Its name is derived from its shape, which looks a bit like a mouse. As you move the mouse, the pointer on the display screen moves in the same direction. Trackball: A trackball is an input device used to enter motion data into computers or other electronic devices. It serves the same purpose as a mouse, but is designed with a moveable ball on the top, which can be rolled in any direction Touchpad: A touch pad is a device for pointing (controlling input positioning) on a computer display screen. It is an alternative to the mouse. Originally incorporated in laptop computers, touch pads are also being made for use with desktop computers. A touch pad works by sensing the user’s finger movement and downward pressure. Touch Screen: It allows the user to operate/make selections by simply touching the display screen. A display screen that is sensitive to the touch of a finger or stylus. Widely used on ATM machines, retail point-of-sale terminals, car navigation systems, medical monitors and industrial control panels. Light Pen: Light pen is an input device that utilizes a light-sensitive detector to select objects on a display screen.    1.4.3 5 5/12 introduction To Computers Magnetic ink character recognition (MICR): MICR can identify character printed with a special ink that contains particles of magnetic material. This device particularly finds applications in banking industry. Optical mark recognition (OMR): Optical mark recognition, also called mark sense reader is a technology where an OMR device senses the presence or absence of a mark, such as pencil mark. OMR is widely used in tests such as aptitude test. Bar code reader: Bar-code readers are photoelectric scanners that read the bar codes or vertical zebra strips marks, printed on product containers. These devices are generally used in super markets, bookshops etc. Scanner: Scanner is an input device that can read text or illustration printed on paper and translates the information into a form that the computer can use. A scanner works by digitizing an image. b) Output Devices: Output device receives information from the CPU and presents it to the user in the desired from. 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 understood by the user. The output is usually produced in one of the two ways – on the display device, or on paper (hard copy). Monitor: is often used synonymously with “computer screen” or “display.” Monitor is an output device that resembles the television screen It may use a Cathode Ray Tube (CRT) to display information. The monitor is associated with a keyboard for manual input of characters and displays the information as it is keyed in. It also displays the program or application output. Like the television, monitors are also available in different sizes. Printer: Printers are used to produce paper (commonly known as hardcopy) output. Based on the technology used, they can be classified as Impact or Non-impact printers. Impact printers use the typewriting printing mechanism wherein a hammer strikes the paper through a ribbon in order to produce output. Dot-matrix and Character printers fall under this category. Non-impact printers do not touch the paper while printing. They use chemical, heat or electrical signals to etch the symbols on paper. Inkjet, Deskjet, Laser, Thermal printers fall under this category of printers. Plotter: Plotters are used to print graphical output on paper. It interprets computer commands and makes line drawings on paper using multicoloured automated pens. It is capable of producing graphs, drawings, charts, maps etc. Facsimile (FAX): Facsimile machine, a device that can send or receive pictures and text over a telephone line. Fax machines work by digitizing an image. Sound cards and Speaker(s): An expansion board that enables a computer to manipulate and output sounds. Sound cards are necessary for nearly all CD-ROMs and have become commonplace on modern personal computers. Sound cards enable the computer to output sound through speakers connected to the board, to record sound input from a microphone connected to the computer, and manipulate sound stored on a disk. 6 6/12 introduction To Computers 1.5 HARDWARE and SOFTWARE Hardware: The physical components of the computer are known as ―Hardware‖. It refers to the objects that we can actually touch. Ex: input and output devices, processors, circuits and the cables. Software: Software is a program or set of instructions that causes the Hardware to function in a desired way. The basic difference between the Hardware and Software is just the same as that exists between TV and TV studio. Without TV studio (software) from where the programs are telecast, the TV (Hardware) is a dead machine. There are five categories of software. They are: 1. Operating System 2. Translators 3. Utility programs 4. Application programs 5. General purpose programs Operating System (OS) : The software that manages the resources of a computer system and schedules its operation is called Operating system. The operating system acts as interface between the hardware and the user programs and facilitates the execution of programs. Generally the OS acts as an interface between the user and the Hardware of the computer. i.e It is a bridge between the user and the Hardware. The User interface provided by the OS can be character based or graphical. CUI -- Character user Interface GUI -- Graphical user Interface CUI : It is operated with keyboard only. Ex: MS-DOS, UNIX GUI : The system can be operated with mouse and keyboard. Ex: Windows 95, Windows XP etc Disk Operating System (DOS): It was developed as early as 1980 by Bill Gates at the age of 19. It is suited for personal computers. Dos is a single user and single task operating system WINDOWS : It works with DOS and it supports single user and multitask system. It requires a powerful PC with a minimum RAM of 8 MB . UNIX AND XENIX: It is suited for multi-user and multi-task system 1.6 Classification of Computers Computers are classified according to the storage capacity, speed and the purpose for which they are developed. These can be classified into three types: 1. Analog Computes 2. Digital Computers 3. Hybrid Computers 1. Analog computers: They operate by ―measuring‖ instead of ―counting‖. The name (derived from greek word analog) denotes that the computer functions by establishing similarities between the two quantities. They are powerful tools for solving differential equations. 2. Digital Computers: These computers operate by ―counting‖. All quantities are expressed as discrete digits or numbers. These are useful for evaluating arithmetic expressions and manipulations of data. 3. Hybrid Computers: Computers which combine the features of analog and digital computers are known as Hybrid computers 7 7/12 introduction To Computers A majority of the computers that are in use are digital. These computers were essentially developed for computations. Later, the developments in the computers led to the use of digital computers in variety of applications. Depending on the use of applications, the digital computers are classified into 1) Special Purpose Computers and 2) General Purpose Computers a) Special Purpose Computers: These are developed with a specific purpose. Some of the areas where these computers are being used are – soil testing, drip irrigation, medical scanning, traffic signals, spacecraft, rocket technology etc., b) General Purpose Computers: These are developed to meet the requirements of several areas such as simulation, solving mathematical equations, payroll and personnel database. These computers are available in different sizes and capabilities and are further classified (based on memory, speed, storage) as follows. a) Super Computers b) Mainframe Computers c) Mini Computers d) Micro Computers a) Super Computers: These have extremely large storage capacities and computing speeds which are atleast 10 times faster than other computers. These are used for large scale numerical problems in scientific and engineering disciplines such as electronics, weather forecasting etc.,. The first super computer was developed in U.S.A. by CRAY computers. b) Super Computers: These have extremely large storage capacities and computing speeds which are atleast 10 times faster than other computers. These are used for large scale numerical problems in scientific and engineering disciplines such as electronics, weather forecasting etc.,. The first super computer was developed in U.S.A. by CRAY computers. c) Mini Computers: It is a medium sized computer with moderate cost, available indigenously and used for large volume applications. It can serve multi-users simultaneously d) Micro Computers: A micro computer is the smallest general purpose processing system. Micro computers are also referred as ―personal computers‖(PC). These are self contained units and usually developed for use by one person at a time but can be linked to very large systems. They are cheap, easy to use even at homes and can be read for variety of applications from small to medium range. 8 8/12 introduction To Computers 1.7 PERSONAL COMPUTERS Personal Computer: A personal computer has a Monitor (VDU), a keyboard , Disk Drive (s), printer and CPU. The CPU of PC has a mother board with several chips mounted on a circuit board. The major components of the circuit board are : Microprocessor, RAM and ROM chips and other supporting circuits. Microprocessor: The Microprocessor chip is like a brain of human being which contains circuits and registers to perform arithmetic, logic and control functions. i.e it contains ALU & CU. These chips will be able to retrieve data from the input output devices, store, manipulate and process a byte of data at a time. There is an address bus which is built into these chips to determine the storage locations (of RAM) of the data and the instructions of the program. Over the years, different microprocessors were developed and the first in the series is INTEL 8080. The other procesors are 8088, 80286, 80386, 80486, Pentium I, II, III and Pentium 4. The Pentium 4 can execute any piece of code that ran on the original 8088, but it does it about 5000 times faster. Clock Speed: The speed with which the instruction is executed or number of pulses per second is called the clock speed. It is measured in terms of million pulses per second (MHZs). 1.7.1 Working with personal computers Drives of the computer: A computer can have Floppy Disk Drive along with Hard Disk drives in the system. These are referred as follows: Floppy Disk Drive : A or B Hard Disk : C Booting of the Computer: Booting imply ―activating‖ the computer for working. Thus, when the computer is switched on, the operating system residing in the floppy or in the hard disk is transferred into the primary memory. After this, the computer is ready to accept the commands at user terminal. If OS is not existing either in floppy drive or in the hard disk drive, ― nonsystem or disk error‖ is flashed on the screen. The booting of the computer is carried out with a software which resides on ROM chip called BIOS ( Basic Input Output System). Thus when a PC with system disk either in Hard-Disk Drive or Floppy Drive is switched ―on‖, the screen finally displays one of the following symbols with a blinking cursor at its end: a) A:\> This imply that the computer is booted through Floppy drive `A‘ and is ready to accept DOS commands. The symbol ―\>‖ is referred as DOS prompt from where DOS commands can be entered. b) C:\> It imply that the PC is booted through the Hard-Disk Drive `C‘. Booting is essential whenever the system is locked or switched-off. A PC can be booted through two ways: a) Cold Booting b) Warm Booting. a) Cold Booting: It is only switching OFF the system and after some time again switching ON. b) Warm Booting: It is carried out by pressing the following three keys simultaneously : Ctrl + Alt + Del. It is preferable to cold booting as it safeguards the system from sudden power fluctuations resulting out of switching ON and OFF the system. 9 9/12 introduction To Computers 1.8 GENERATIONS OF COMPUTER Introduction: A computer is an electronic device that manipulates information or data. It has the ability to store, retrieve, and process data. Nowadays, a computer can be used to type documents, send email, play games, and browse the Web. It can also be used to edit or create spreadsheets, presentations, and even videos. But the evolution of this complex system started around 1940 with the first Generation of Computer and evolving ever since. There are five generations of computers. 1. FIRST GENERATION Introduction: 1. 1946-1959 is the period of first generation computer. 2. J.P.Eckert and J.W.Mauchy invented the first successful electronic computer called ENIAC, ENIAC stands for “Electronic Numeric Integrated And Calculator”. Few Examples are: 1. ENIAC 2. EDVAC 3. UNIVAC 4. IBM-701 5. IBM-650 Advantages: 1. It made use of vacuum tubes which are the only electronic component available during those days. 2. These computers could calculate in milliseconds. Disadvantages: 1. These were very big in size, weight was about 30 tones. 2. These computers were based on vacuum tubes. 3. These computers were very costly. 4. It could store only a small amount of information due to the presence of magnetic drums. 5. As the invention of first generation computers involves vacuum tubes, so another disadvantage of these computers was, vacuum tubes require a large cooling system. 6. Very less work efficiency. 7. Limited programming capabilities and punch cards were used to take inputs. 8. Large amount of energy consumption. 9. Not reliable and constant maintenance is required. 2. SECOND GENERATION Introduction: 1. 1959-1965 is the period of second-generation computer. 2. Second generation computers were based on Transistor instead of vacuum tubes. Few Examples are: 1. Honeywell 400 2. IBM 7094 3. CDC 1604 4. CDC 3600 5. UNIVAC 1108… many more 10 10/12 introduction To Computers Advantages: 1. Due to the presence of transistors instead of vacuum tubes, the size of electron component decreased. This resulted in reducing the size of a computer as compared to first generation computers. 2. Less energy and not produce as much heat as the first genration. 3. Assembly language and punch cards were used for input. 4. Low cost than first generation computers. 5. Better speed, calculate data in microseconds. 6. Better portability as compared to first generation Disadvantages: 1. A cooling system was required. 2. Constant maintenance was required. 3. Only used for specific purposes. 3. THIRD GENERATION Introduction: 1. 1965-1971 is the period of third generation computer. 2. These computers were based on Integrated circuits. 3. IC was invented by Robert Noyce and Jack Kilby In 1958-1959. 4. IC was a single component containing number of transistors. Few Examples are: 1. PDP-8 2. PDP-11 3. ICL 2900 4. IBM 360 5. IBM 370… and many more Advantages: 1. These computers were cheaper as compared to second-generation computers. 2. They were fast and reliable. 3. Use of IC in the computer provides the small size of the computer. 4. IC not only reduce the size of the computer but it also improves the performance of the computer as compared to previous computers. 5. This generation of computers has big storage capacity. 6. Instead of punch cards, mouse and keyboard are used for input. 7. They used an operating system for better resource management and used the concept of time-sharing and multiple programming. 8. These computers reduce the computational time from microseconds to nanoseconds. Disadvantages: 1. IC chips are difficult to maintain. 2. The highly sophisticated technology required for the manufacturing of IC chips. 3. Air conditioning is required. 11 11/12 introduction To Computers 4. FOURTH GENERATION Introduction: 1. 1971-1980 is the period of fourth generation computer. 2. This technology is based on Microprocessor. 3. A microprocessor is used in a computer for any logical and arithmetic function to be performed in any program. 4. Graphics User Interface (GUI) technology was exploited to offer more comfort to users. Few Examples are: 1. IBM 4341 2. DEC 10 3. STAR 1000 4. PUP 11 … and many more Advantages: 1. Fastest in computation and size get reduced as compared to the previous generation of computer. 2. Heat generated is negligible. 3. Small in size as compared to previous generation computers. 4. Less maintenance is required. 5. All types of high-level language can be used in this type of computers. Disadvantages: 1. The Microprocessor design and fabrication are very complex. 2. Air conditioning is required in many cases due to the presence of ICs. 3. Advance technology is required to make the ICs. 5. FIFTH GENERATION Introduction: 1. The period of the fifth generation in 1980-onwards. 2. This generation is based on artificial intelligence. 3. The aim of the fifth generation is to make a device which could respond to natural language input and are capable of learning and self-organization. 4. This generation is based on ULSI(Ultra Large Scale Integration) technology resulting in the production of microprocessor chips having ten million electronic component. Few Examples are: 1. Desktop 2. Laptop 3. NoteBook 4. UltraBook 5. Chromebook… and many more Advantages: 1. It is more reliable and works faster. 2. It is available in different sizes and unique features. 3. It provides computers with more user-friendly interfaces with multimedia features. Disadvantages: 1. They need very low-level languages. 2. They may make the human brains dull and doomed. 12 12/12