INTRODUCTION TO INFORMATION AND COMMUNICATION TECHNOLOGY(GST

Transcription

1 INTRODUCTION TO INFORMATION AND COMMUNICATION TECHNOLOGY(GST 115) Supplementary Lecture Note 1 Afe Babalola University, Ado-Ekiti, Nigeria Lecturer : Oguntimilehin A THE COMPUTER SYSTEM Computer is a programmable electronic device which accepts, processes, retrieves, stores data and generates output (information) reports with high speed and accuracy. PARTS OF COMPUTER Computer system has four essential parts, they are (i) Monitor (ii) Central Processing Unit (CPU) (iii) Key board and (iv) Mouse. Central Processing Unit Monitor Mouse Key board MONITOR:- Monitor is also called the visual display unit (VDU)or Cathode Ray Tube (CRT). It looks like television in shape. It displays input and output information. When you type your name using the keyboard, you see it on the monitor. Black and white monitor is called monochrome while the coloured monitor is simply called colour monitor. Monitor are of different sizes.12, 14, 15, 17, 19, 21, etc. (12 means 12inch) Liquid Crystal Display (LCD) technology is used in flat monitors CENTRAL PROCESSING UNIT (CPU):- CPU is also called system unit. This is the nerve center of a computer system. It is the place were processing is done. It is the most essential part of the computer system. No CPU means no computer. CPU alone can work on its own while other parts cannot work without the CPU. The CPU with flat casing is called desktop case system unit, while the tall casing is called Tower case system unit. CPU is called the brain of a computer system KEY BOARD:- This is one of the mostly used input devices. It allows data to be keyed directly into the CPU from the key terminals. The computer keyboard resembles the typewrite keys but different form it in many ways. Some keyboards have functions that can perform the function of a mouse. The first key on keyboard is the Escape key. It is used to terminate or stop the computer from doing what it is currently doing. HISTORY OF COMPUTER The term computer is the outcome of simple tools for counting in the olden days, and even up today. These simple tools are called early aids to counting. Early aids to counting The early aids to counting include: Fingers, beads, stones or pebbles, sticks and so on. ABACUS:- The next idea was to use coloured beads held on a string. The Chinese used this method to count. The beads were threaded on line of wire frame. The frame is divided by a

2 cross number so that each row of beads has a sector. The sector may have one bead up and six beads below and another sector with four or sometime, five beads. The bead on the first line counted the units, the beads on the second wire counted the tens. The beads on the third wire counted the hundreds, the fourth wire counted the thousands and so on. By moving the beads back and forth along the wire, numbers could be added and subtracted. This device was called ABACUS. NAPIER S RODS The Napier s rod was developed in 1617 by a Scottish mathematician and politician. The Napier s rod was constructed from stripes of wood and bone. Mechanical multiplication, division and taking squre roots of large numbers were done with the use of Napier s rod. He also published the logarithmic tables called Nepearian logarithms. THE SLIDE RULE The development of slide rule was a further development or improvement on logarithms. This was conceived by Rev. William Oughtred. The slide rule which behaved like analogue computer, performed multiplication and division by addition and subtraction of log tables PASCAL S ADDING MACHINE (PASCALINE) Blaise Pascal 1642 in France invented a machine that could do both addition and subtraction. The machine had wheels and teeth. The first wheel counted unit, second tens, third hundreds and so on. Every time, the first wheel made a complete turn, the second wheel moved one position. Ten turns on the first wheel caused one complete turn on the second wheel. One hundred turns on the first wheel caused ten turns on the second wheel and one complete turn on the third wheel. By looking at the position of each wheel, you can read a number from them. Examples nowadays are used in wall clock, fuel and electric maters. By moving the wheels forward you add, and when wheels are moved backward, you subtract. Pascaline was built when Pascal was only 19 years old to help his father a tax collector for the French Government. Programming language Pascal was named after him in his honour. LEIBNIZ CALCULATING MACHINE The great German Mathematician Baron Gottfried Leibniz ( ) built another mechanical machine that could multiply and divide as well. He used pascal s ideas to create this. This device could then add, subtract, multiply, divide and calculate square roots JOSEPH JACQUARD PUNCHED CARDS In the early 19 th century French inventor Joseph-Marie Jacquard devised a specialized type of computer, a silk loom. Jacquard s loom used punched card to program patterns that helped the loom create woven fabric. Although Jacquard was rewarded and admired by French Emperor Napoleon I for his work, he fled for his life from city of Lyon pursued by weavers who feared their jobs were in jeopardy due to jacquard s invention. The loom prevailed, however. When jacquard died, more than 30,000 of his looms existed in Lyon. The looms are still in use today especially in the manufacture of fine furniture fabrics. The first punched card was thus invented by jacquard CHARLES BARBAGE S DIFFERENCE ENGINE Another early mechanical computer was the difference engine, designed in the early 1020s by British mathematician and scientist Charles Babbage. Although never completed by

3 Babbage. The difference engine was intended to be a machine with a 20-decimal capacity that could solve mathematical problems. Babbage also made plans for another machine, the analytical engine, considered the mechanical precursor of the modern computer. The Analytical engine was designed to perform all arithmetic operations efficiently; however; Babbage s lack of political skills kept him from obtaining the approval and funds to build it. Augusta Ada Byron was a personal friend and student of Babbage. She was one of only a few woman mathematician of her time. she prepared extensive notes concerning Babbage s ideas and the Analytical Engine. Programming language (Ada) was named in honour of her for her conceptual programs for the machine. Although the Analytical Engine was never built, its key concepts, such as the capacity to store instructions, the use of punched cards as a primitive memory, and the ability to print, can be found in many modern computers. HOLLERITH S MACHINE Herman Hollerith ( ), American inventor, born in Buffalo, New York, and educated at Columbia University, who devised a system of encoding on cards through a series of punched holes. This system proved useful in statistical work and was important in the development of the digital computer. Hollerith s machine, used in the 1890 U.S. census, read the cards by passing them through electrical contacts. Closed circuits which indicated hole positions, could then be selected and counted. His Tabulating machine company (1896) was a predecessor to the International Business Machine Corporation (IBM) TURING MACHINE In 1936 British mathematician Alan Turing proposed the idea of a machine that could process equations without human direction. The machine (now known as a Turing machine) resembled an automatic typewriter that used symbols for math and logic instead of letters. Turing intended the device to be a universal machine that could be used to duplicate or represent the function of any other existing machine. Turing s machine was the theoretical precursor to the modern digital computer. The Turing machine model is used by modern computation theorists MODERN COMPUTER The threat of war speeds up technology, and computer technology has always obeyed the rule. The first completely automatic digital computer was invented by Dr Howard Aiken of Harvard University. It was called mark 1. Alken began work on it in 1937 and completed it with US Navy financing it in Mark 1 was very big and it could not store information internally. Programming was done by a punched paper tape fed into the machine. Its internal operations were performed electronically, but its arithmetic counters were mechanical. Therefore it was not an electronic computer, in fact it was more closely resemble Sir Babbage s Analytical Engine. The first electronic computer for general purpose use was Electronic Numeric Integrator and Calculator (ENIAC) (1945). Credit for the next great innovation in computer technology goes to the mathematical genius John Von Neuman, who, in a paper written in 1945 with collaborators at the institution for Advanced Studies presented two basic ideas one (Rediscovering and extending Atanasoft s ideas), that the binary number system be built into computers. This replacing the decimal of 0 to 9 with two digits 0 and 1. The binary system corresponds to the on and off positions of all electronic computer design. The other (second) idea Von Neuman and his colleagues presented was the concept of stored program. Computers had always been designed to store numbers in their memories but

4 early computers up to and including electronic computer such as ENIAC had to be totally rebuilt (rewired) before they could start work on a new problem A stored program computer is far more flexible. To begin with, certain basic circuits and therefore basic operations are built in. Solving a new problem requires a new set of instructions called a program to call up the basic operation in any desired order and perform any task of which the computer is capable. For this reason, a stored program computer can turn from one task to a different one whenever a new set of instructions (program) is fed into its memory. The first computer capable of storing instructions and data in its memory was EDSAC It became the first stored program computer built at Cambridge University in England in EDVAC, another stored program computer was built by Mauchly and Eckert (1946). Mauchly and Eckert further worked on UNIVAC (Universal automatic Computer) and made it ready for use by the census Bureau in 1951 and it was first fully electronic stored program digital Computer to be made commercially available. It was also the first to be bought by a business organization for data processing. UNIVAC head program was Dr Grace Hopper who has been the first programmer of mark 1. Dr Hopper made significant contributions toward the development of the programming language COBOL (Common Business Oriented Language). The concept of stored program is now being used by all the present computer system. GENERATIONS OF COMPUTER The series of computer from the day of invention of computer till today can be grouped into five generations. FIRST GENERATION COMPUTER ( ) The first generation of computers are valve (vacuum tubes) based machines. Characteristics of First Generation Computers (i) They were large in size (ii) They consumed large amount of energy (iii) They produced much heat (iv) They were programmed using machine language (0 and 1) (v) They were valve based machines (vi) They had limited internal memory (vii) The were very slow in operation (viii) Punched cards were used to enter data into the system. (ix) They were not reliable Examples of the first generation computers are IBM650, ENIAC, MARK 1, UNIVAC SECOND GENERATION COMPUTER ( ) Second generation computers used transistors as switching device instead of vacuum tubes Transistors are smaller and they are fast and more reliable. They produced less heat during the operation. The transistor was invented in 1948 by a team of scientists headed by williams Shockley in United States of America. Transistors are made from material called semiconductor (silicon and germanium) Characteristics of second generation computers (i) They used high level language such as COBOL, FORTRAN (FORMULA TRANSLATOR) (II) The were smaller in sizes (iii) They used transistors (iv) They consumed less electricity (power)

5 (v) They employed magnetic core for internal storage. (vi) They used external storage to supplement internal storage e.g. magnetic disks (vii) They required less air conditioning. (x) They were more reliable than the first generation computers. Examples of second generation computers: Honey Well 400, Honey Well 800, IBM 401 THIRD GENERATION COMPUTERS ( ) The Third Generation computers began in 1964 with the IBM (International Business Machine) 360 mainframe family. They made use of integrated circuit (IC). Features / Characteristics of Third Generation Computers 1. They have larger memory sizes and they are cheaper in term of cost per byte. 2. They performed more accurately. 3. Integration of hardware and software. 4. Ability to perform several operations simultaneously. 5. Data communication advances. 6. Increased internal storage capacity. 7. Increased speed of processing. Examples of the third generation computers are IBM 360 series, ICL 1900 FORTH GENERATION COMPUTER 1971 PRESENT The 4 th generation computer made use of large scale integrated circuit (LSIC) which makes possible the design of smaller computers which are described as micro-computers. The noticeable development of this generation includes the following: (i) Use of Large scale integrated circuit (ii) User friendly, menu drives, interactive and intelligent software system such as spread sheets, data base management system, word processing packages, desktop publishers. (iii) Faster memories (iv) (v) Mass memories. Highly improved building block with emphasis on standard and compatibility of both hardware and software system. It enhances pipelining and parallel processing FIFTH GENERATION,COMPUTER (1990-?) The fifth generation computer are the computer which are widely applied in business data processing, mathematical statistical calculations in sciences and engineering. The 5 th generation computers are based on a new architect which shipment very large memory, high parallel processing, text editing, image processing and reasoning. They can learn, associate, make inferences, take decisions and otherwise behave in such ways that, they are considered the exclusive province of human expert of a problem domain. They store information in a data base which enables processing to be carried out efficiently. The fifth generation computer is therefore intended to be intelligent as human being. Features of The Fifth Generation Computers (i) knowledge of processing and inference procedural capability. (ii) Integration with telecommunication technology such as telephone, radio and satellite (iii) Image processing (iv) Very high parallel processing and pipelining (v) (vi) Logic programming Text analysis and synthesis. ORGANIZATION OF A COMPUTER SYSTEM Physical Components of a Computer System CPU (Central Processing Unit) Control Unit

6 A computer system is made up of the central processing unit (CPU), visual display unit (VDU), key board, mouse, software and other peripherals such as speakers, scanners and printers etc. A system is an organized way of doing things. It is the interrelationship of objects in achieving a common goal. System could be made up of sub-system or components, which worked together for a common goal. Computer system therefore refers to the group of components that are working together in a regular relation to generate the required output. The two components of the computer system are the hardware and software. live wire refers to the people operating the computer system. Human beings cannot be a part of a machine. HARDWARE COMPONENTS The hardware is the machinery part of the computer system. The equipment you use, the parts you can touch or break. The computer hardware consists of the central processing unit and the peripheral units such as key board,speaker, monitor (VDU),printer, scanner and mouse which are used to get data into and out of the computer system. The central processing unit. This is the nerve centre of a digital computer and it contains three parts, they are: (i) Main memory (ii) Arithmetic and Logic unit (ALU) and (iii) control Unit. Functions of CPU (i) It temporarily stores the programs and data currently being used so that the computer can quickly access the information. (ii) In connection with the operating system, it coordinates all of the computer s activities, for example retrieving files from the disk, interpreting data and commands entered from key board (Input Unit) and sending data to the output devices such as printer. (iii) It performs arithmetic calculations such as addition and subtraction using binary system of mathematics. (iv) It performs logical operations using equal to, greater than and less than comparison. (i) Memory Unit The memory unit is the section of the system where data, instruction and output are stored or held during processing, or for onward transfer to either the control unit or the ALU or even to an output device.

7 Data and programs are held in the internal storage until required. The memory of computer can be classified into (3) three, namely: primary memory, secondary memory, which is divided into Random Access Memory (RAM) and Read Only Memory (ROM). RAM: RAM stores data temporarily while a program is being run it enables information to be erased or overwritten while the user is processing data on the computer. RAM is highly volatile, it looses information easily as a result of power failure. It enables the user to read and also write information whenever he requires. The storage facility is very limited; it is the main or primary or user memory. Read only memory (ROM): It is static, non-volatile memory. It is a permanent storage medium on chips that contain instruction and data, which are used permanently on the computer Users can read it but the user cannot change it. Data is permanently recorded on memory chips and turning the computer off does not affect it. ROM is generally used to store permanent information needed by the computer for example it contains the initial programs code, the instruction computer must follow to start up when you first turn it on. The content of ROM can only be accessed and read by the users, It cannot be modified or erased at userlevel. Unlike RAM, it is not volatile in nature. it provides access to time to information. Tertiary memories: Tertiary memories are located outside the processor and are not connected directly to the processor. It supports off line processing of data. It has a lower access time to information than secondary memory. Examples are punch cards,computer (flow line) papers, magnetic tape, floppy disk and magnetic disk pack, flash drive e.t.c (ii) Arithmetic And Logic Unit (ALU) Calculations and comparison are done in this unit. Its arithmetic sub unit enables the operations of addition, subtraction, multiplication and division while its logic sub unit provides the computer ability to test various additions and take specific actions. One may be interested in testing certain conditions. The ALU includes Registers, Adders and counter. A register receives, holds and transfers data as directed by the control unit. An adder receives information from two or more sources. It performs the necessary arithmetic operations on the data and sends the results to a register. A counter counts the number of times an operation is performed. (iii) Control Units:- It directs the sequence of operations,interprets the codes/ instructions and sends signal / commands to other devices. Functions of control unit i. It directs the input devices to read data into the memory. ii. It instructs the ALU- Arithmetic and Logic unit as to what operations to perform on data stored in the memory and where to store the calculated results in the memory. iii. It instructs the output devices, what information is to be printed and on what medium to record it. The Pheripheral Units The Pheripheral Units are of three types, they are: (i) Input devices (ii) Output devices (iii) Auxiliary storage devices. (i) Input devices: These are the devices used to enter data into the computer system. e.g key board, mouse, light pen, joystick, voice input. (ii) Output devices: Output devices help to bring out processed information from the processing unit to the outside world e.g printers, VDU. Microfilm recorder, magnetic tapes, magnetic disk and diskettes. (iii) Auxiliary Storage or Backing Storage Auxiliary Storage is used to provide mass storage for programs and files which are not currently being operated on but which will be transferred to the main storage when

8 required. The devices include microfilm, magnetic tape unit, magnetic disk unit and floppy disk unit. SOFTWARE COMPONENTS Software is the set of instructions called program that is used to instruct the computer what to do and when to do it. The software is designed to exploit and provide the potential capabilities of the hardware to the user. Software can be classified into two major groups: (i) System Software: The computer manufacturer usually provides this. It is made up of mostly programs that contribute to the control and performance of the computer system. Computer user cannot modify it. It controls the programs used by computer users and hardware components. (ii) Application Software: They are usually produced by the users. It may also be produced by computer manufacturer or supplier. The computer user develops his own software to meet his personal or corporate needs. Application software are further divide into (i) User application Program (ii) Application Packages. CHARACTERISTICS / ADVANTAGES OF A COMPUTER SYSTEM. (i) Accuracy (ii) Versatility (iii) Very High speed (iv) Storage facility (v) reliability (vi) Programmability. CLASSIFICATION OF COMPUTERS Computer may be classified according to (a) Types / Method of data representation (b) Purpose (c) Size of computers. (a) TYPES OF COMPUTERS: The three types of computer are (i) Digital (ii) Analog (iii) Hybrid (i) Digital computers: These are the type of computers used to process numeric information. Digital computer uses a very simple number system known as binary which deals with two characters only 0 (zero) and 1 (one) to represent numbers, letters and symbols. Digital devices include: wrist watch and light switch. (ii) Analogue /Analog Computers: There are some things that cannot be counted in order to know their values. e.g. water oil, speed of a moving object, heat, height. These are continuous objects. We can only measure these objects in volume. Computers that handle such thing are called analogue computers. Analog computers accept quantities varying over a length of time rather than a series of distinct items with a unique value. They are used to measure physical quantities that are in continuous form e.g Temperature, pressure, voltage, electric current, speed. Examples of analog devices are electric meter, speedometer, length scale, barometer. (iii) Hybrid Computer: These are the type of computers which combine both the properties of digital and analogue computers. Hybrid computation involves converting digital computer to analog computer and similarly converting analogue computer to digital computer using a device called MODEM (Modulator and Demodulator) (B) CLASSIFICATION ACCORDING TO PURPOSE There are two main classifications under purpose (i) Special purpose (ii) General purpose (i) Special Purpose: These are the computers designed for a specific problem e.g computer designed for accounting problem, weapon Guidance system, Electronic wrist watch etc. (ii) General Purpose Computers: These are the computers designed to solve a wide range of problems. Special programs are written to provide solution for each of the problems. Such computer can be used for word processing, Accounting, Statistics, computer-aide design etc. (C) CLASSIFICATION OF COMPUTER ACCORDING TO SIZE

9 (i) (ii) (iii) (iv) Main Frame: They have very large size and they are early computers. They are some how electro-mechanical devices. The users do not have direct interactions with the computers. There are input output clerks, computer operators, Data entry operators, system Analysts and computer programmers which are lined up between the computer users. Main Frame computer supports multiple programming, that is, two or more programs or jobs can be run on a mainframe computer simultaneously. Minicomputers: They are physically smaller and cost far less than mainframe, yet they are very powerful to do many of the jobs that only big mainframe computer could do. supercomputers: The end result of the need for large and faster computers in scientific applications is the supercomputer. The development of supercomputers emphasizes parallel processing and pipelining. Microcomputers: These are usually referred to as personal computers (PCS). They range from the type that can be kept on a desk to models like brief cases and that which can be kept in the palm. Microcomputers support mono programming, that is, only a program or job can be run on them at once. Microcomputers are capable of performing operations like the mainframe or minicomputers. They are user friendly. Microcomputers are the smallest, least expensive of all computers. INPUT / OUTPUT DEVICES Input devices: These are the computer devices, which are used to enter data and information into the computer system. Some examples of input devices are: 1. The keyboard: This is one of the mostly used input devices. It allows data to be keyed directly into the CPU from the key terminals. The computer keyboard resembles the typewriter keys but different from it in many ways: some keyboards have functions that can perform the function of a mouse. ii. Mouse: This is the second most commonly used input devices. The device is called mouse because its shape looks so much like that of a rat,. when mouse is dragged on the mouse pad, it moves the cursor. Mouse can move the cursor in any direction. Icons characters are quickly located with mouse. iv. Light Pen: Light pen, as the name sounds and connotes is a PEN that works by light or current or electricity. It works in conjunction with special monitor called GRAPHICS VISUAL DISPLAY UNIT (GVDU). The GVDU has special feature of hardware and software that is capable of detecting the light coming from the ball point end of the light pen. If you had played on the sand, you must have drawn things on it. The GVDU serves as sand while the light pen serves as your finger. v. Scanner: The scanner is a camera, which is capable of taking the photograph of an object, and then pass it into the computer memory or storage for further processing. When this is done, the computer can modify the picture in so many ways. The scanner is connected to the system unit just as the other peripherals are. Scanner can scan a section of a photograph by selecting the required area out of the whole. Photocopier cannot do this. vi. Voice Input: Quality of voice input data can never be as the original voice due to the conversion to binary code done by the digitizing sound sampler. The wavelength and height determine the generated voice. vii Card Reader: This is another Input device which works by recognizing holes in a small card. OUTPUT DEVICES

10 Output devices are the tools used to get out the result of the processed data called out put (information)from the computer system. Output devices include: monitor (VDU), printer, plotter, speaker and microfilm. i. Monitor: It displays the output or information on its screen. Such copy is called soft copy. Its shape is very close to that of television. If a copy of what can be seen on the screen is required on paper, it can be obtained from either a printer or a plotter or from a turtle. Copy on paper of programs from a CPU is called hard copy. ii. Printer: The printer displays the output from a computer system unit on a paper. The paper is generally called a flow line and also called hard copy. Printers can be classified into two categories. (i) Impact printers and (ii) Non Impact printers. (a) Impact Printers: These are the printers that print character, they use carbon papers or ribbons to transfer impression on the paper or flow line. Each head is hit by a hammerhead against a carbon paper to make the character visible. e.g line printers, daisy wheel printers and dot matrix printers. (b) Non-Impact Printers: These have no character head (s) do not use carbon paper but rather TONER (liquid ink) through electronic beams e.g ink jet printers, thermal printers, laser printer. iii.. Plotters: The plotters are the right devices for drawing pictures and graphs. Plotters are usually called graph plotters. Plotters use pen that can move in different directions. However there are plotters that use electrostatic printing rather than pen and ink. Colour graph plotters use many pens, each for a colour instead of one pen. iv. Speaker: The output device that provides sound information is the speaker. The system unit output, which is in digital form, passes through a digitizing sound sampler which produces a waveform. The waveform is connected to a vibrator, which produces sound.the sound we hear is nothing but vibration received by the eardrum. v. Computer output on microfilm (COM): Modern, high resolution photographic film is capable of storing large quantities of data in readable character form in a relatively small space, and is consequently useful as an output medium for data that is required to be stored (archived) or sent by post. Photographic output takes two forms; microfilm and microfiche.