Basic Computer Science for Beginners

By Kingsley Idiagbor, B.Sc(Hons), PGDCs

December 20021

COMPUTER DEFINITION: Computer is an electronic machine used for processing data, store and produce an output to the user DATA: Data is the raw information that is fed into the computer. Data comes in three forms: letters (like a,b,c..) numerals (such as 1,2,3...) and special characters (e.g. $, @,/ ..) INPUT: Input is the process of feeding data into the computer. OUTPUT: is the processed data that is communicated to the user. The output is also

Input

Process

Output

Storage CATEGORIES OF COMPUTER There are four major categories of computer: Microcomputers: are further These are computer into systems palmtop, that have the microprocessor in one case.They subdivided notebook, laptop and desktop computers.

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2. Minicomputers:

These are more powerful than the

microcomputers and can support a number of users performing different tasks. Most powerful mini-computers are called super mini-computers

3.

Mainframe:

They are large systems that can

handle hundreds of users. They store large amounts of data and process transactions at high rate. Mainframes require several rooms to store. 4. used Super-computers: for such applications They are the most powerful as weather forecasting, category of computers and also the most expensive. They are engineering designs and testing, space exploration and other tasks, which require long and complex calculations. TYPES OF COMPUTER We have three different kinds of computers: i) ii) iii) Analog computers; Digital computers and Hybrid computersThese are devices that measure one form of physical quantities or another like temperature, pressure, speed and so on. Examples of analog computers are thermometer, barometer, speedometer and hygrometer

Analog computers

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Digital computers: These are devices that are used for counting. Examples include adding machine, billing machine, electronic wrist-watch and calculator Hybrid computers These devices combine the functions of measuring physical quantities as well as counting. Electronic computers like desktop computers and notebooks are examples of hybrid computers PARTS OF A COMPUTERThere are four major parts of a computer: 1. Monitor; 2. System Unit (which contains the CPU,hard disks & others) 3. Disk drive (provides slot for diskettes) 4. KeyboardMonitor

System Unit Disk drive Keyboard

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PERIPHERALS These are those external devices that must be attached to the System unit for them to work. Examples of Peripherals: i) mouse; ii) light pen; iii) printer; iv) plotter; v) modem (modulator-demodulator); vi) UPS (Uninterruptible power supply); vii) scanner; viii)telephone; ix) data projectors; x) microphone among several others. Some peripherals, not a major part, are becoming indispensable features of a modern PC (Personal Computer). Examples are the mouse, scanner and printer HARDWARE This is the physical component of the computer which we can see and touch Hardware is made up of four types of devices or units. These include: input devices, processing devices, output devices and storage devices. INPUT DEVICES Input devices are those devices that are used for feeding in data into the computer. Enlisted below are various input devices: i) keyboard ii) mouse; iii) scanner

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iv) light pen; v) joystick (for playing computer games); vi) voice input; vii) touch screens; viii) trackball; PROCESSING DEVICES These are units that process data from one form to another. The CPU (central processing unit) which is generally regarded as the 'heart' or the 'brain' of the computer, is a major processing device. Another example is the Modem (modulator-Demodulator) which is processes data for communication purpose. The modem enables the computer to dial a telephone or access the INTERNET (more on this later on the course) by dial-up method OUTPUT DEVICES They are devices that computer uses to produce output (information)or the unit that is used to communicate with the user. They may include: a) monitor; b) printer; c) data projectors; d) plotters; e) computer output microfilm;

f) voice output (such as we find in Robot technology)

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STORAGE DEVICES Storage is the fourth and final operation in the information processing cycle (earlier mentioned). As the name implies, storage devices are those devices used for storing data and programs for later use. We have primary storage (main memory inside the system unit) and the secondary storage devices. The latter is sometimes called Auxillary storage. In the section that follows, we are going to look at some of them in detail: MONITOR Monitor is the part of the computer that looks like television set. It is variously called as CRT (Cathode Ray tube), VDU (Visual display unit), Screen or just Display. The output that is displayed on the computer cannot be touched, as it were, and is called soft copy output. Pixel: also called 'picture element are the individual dots that make up the text or graphic and can be illuminated. The greater the number of pixels, the better the screen resolution. Resolution: This is the clarity of a monitor and is determined by the number of pixels that can be illuminated. TYPES OF MONITORS We have two major kinds of monitors: monochrome monitors and colour monitors Monochrome Monitors: They are computer terminals that display a single colour such as amber, green or white on a black background; or black

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characters against white background Colour Monitors They are more expensive than the monochrome monitors and are more desirable because colour enables users to more easily read and understand the information on the screen. Several Graphic standards have been developed and they include: CGA: (Colour Graphics Adapter); EGA (Enhanced Graphics Adapter) VGA (Video Graphics Array) SVGA (Super Video Graphics Array) Each standard provides for a different number of pixels and colours and offer even higher resolution screens. With the development of mobile computing in the form of truly portable computers that could be conveniently carried by hand or in a briefcase, came a need for an output display that was equally portable. Today, we have what we call the Flat panel Monitors that are actually LCD (stands for Liquid thin-film Crystal Display) and that plasma makes screens.There are also the TFT (stands for transistors) monitors use of LED (Light emitting diodes).

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Printers Printers are very important peripheral in that they produce hard copy output that the user can carry about unlike the soft copy output from monitors. How are Printers Classified? Printers can be classified by how they transfer characters from the printer to the paper. This is either by impact or non-impact Impact printers These transfer the image onto the paper by some type of printing mechanism striking the paper, ribbon, and character together. Examples of impact printers include: a) b) c) d) There dot-matrix printer daisy wheel printer chain printer band printer are also These a variety of non-impact printer,

Non-Impact printers printers. include ink-jet

thermal printer and page printers like the laser jet printer.

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Choosing a Printer Besides understanding the features and capabilities of the various types of printers that are available, one must consider other factors factors the text before include and choosing how much a printer. output will is Such be very for

produced, the speed as well as the quality of graphics. Laser-jet desirable for printing heavily text documents while ink-jet printer is the best bet graphics intensive documents. Terms associated with Printers DQ NLQ LQ CPS PPM Draft quality Near Letter quality Letter quality Characters per second Papers per minute BRIEF HISTORY OF COMPUTERS Computing has a long history and started with mans search for the best method of easy counting and manipulation of items and number of materials and other resources. The Chinese and the Ancient Babylonians made use of the Abacus. During the renaissance period however, notable scientists like Blas Pascal, James-Marie Jacquard, and Charles Babbage devised better counting devices. We

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had the punched cards by Jacquard, Herman Holleriths tabulating machine that eased the 1890 American census and became the older cousin of the IBM computers. The first electronic computer was the ENIAC and was developed by IBM in the year 1946. They were very large and produced large amount of heat because of the use of vacuum tubes. They were the first generation computers. The development of transistors gave birth to the second-generation computers, which were not as large and produced less heat. In 1969, Ted Hoff invented IC (Integrated circuit) and together with Gordon Moore developed the 8008 microprocessor in INTEL. Microcomputers were born. In 1975, average person could now purchase personal computers. In 1980, IBM gave Bill Gates of Microsoft Corporation, a contract to come out with an operating system. His MS-DOS and later several releases of Windows have changed the face of computing world-over. INTERNET is the information superhighway that started as ARPANET in late 60s but became popular in the mid 1990s. With the advent of INTERNET came e-commerce, email, virtual research, and teleconferencing. Suffice it to say that the INTERNET is perhaps the greatest gift of computing to man and has changed the way that he views his world. COMPUTER TIMELINE [summary] 1400 BC Abacus

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1800 AD

James-Marie Jacquard Weaving1 loom machine /cards

Fig: Jacquards punched cards

1890Charles Babbage [generally as 1890.1924 1937 1946 1952 Father of computer] engine

regarded analytical

Herman Holleriths tabulating machine

Atanasoff-Berry-Computer [ABC] von Neumann & Mauchley ENIAC Grace Hopper programs computer using symbolic code. Note thatAda Lovelace, a woman, was the Fig: Charles Babbages Analytical Engine

first programmer 1957 1958 FORTRAN programming language Computers built with transistors

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1969

Ted Hoff of Intel developed a microprocessor codenamed Intel 4004; ARPANET-forerunner of INTERNET

1970 1975 1976 1980 1981

4th generation computers MITS-the first commercial PC Steve Jobs & Steve Wozniak built the first Apple computer Bill Gates MS-DOS IBM PC introduced

1983 Mitch Kapor Lotus 1-2-3 1984 Apple introduces Mac computers 1989 1990 1995 Intel 80486 microprocessor for 486 computers Microsoft released Windows 3.0 Microsoft released Windows 95 w/ FAT-32 addressing system & Internet browser in one 1995 1996 1997 Pentium technology More domain registration for INTERNET Nanotechnology & miniaturization of computers

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1998

Microsoft released Windows 98

June 4, 2008 What is a program? Program is a set of instructions that are fed into a computer to carry out a task. The computer is lifeless and you can really not do any thing without programs. We can type our letters with the computer because of a program that makes the computer to allow us to do so. The program could be a simple one like instructing the computer to add two numbers together or could be a complex one like forecasting what the weather would be like in Calabar tomorrow. Programming Language If I want you to do something for me, that is an instruction, isnt it? You cannot actually carry out the instruction if you did not understand my language. It is so with the computer, too. To be able to write a program, the instructions should be written in a language that the computer can

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understand easily. Such a language is called a programming language. Examples of programming language1.

BASIC (which stands for Beginners Allpurpose Symbolic Instruction Code) FORTRAN (Formula Translator) COBOL Language) ADA Pascal C C + + (pronounced C plus plus) HTML (Hyper Text Mark-up Language used for web page authoring in the INTERNET) (Common Business Oriented

2. 3. 4. 5. 6. 7.8.

9. 10.

JAVA ALGOL (Algorithmic Language)

There are many other languages that can be used for writing programs. These are just a few of them.

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SOFTWARE Software is the collection of programs in the computer, which we can see at times but cannot touch. Types of software There are three major types of software, namely: a) b) c) System software; Application software and Utility software

System software These are programs that control the operations of any computer. Some of these operations include starting up the computer (booting), loading, executing (that is carrying out instructions). System software includes operating system and language translators or what we call compilers. Some operating systems include: a) MS-DOS [Microsoft Disk Operating System]1

b) c) d) e) f)

WFWG (Windows [3.11] For Work Groups) Windows 95 or 98 Windows 2000 Professional Windows ME (Millennium Edition) Windows XP (Windows Experience)

Application software: These are programs that are designed to carry out specific tasks for us. Application software is sometimes referred to as packages. Again, there are different types of application software namely:a)

Word-processing: This software enables us to type letters, memos and documents. E.g. MSWord, WordStar, WordPerfect, Write, Lotus AmiPro, Windows MultiWrite,

WordPad and so on.b)

Spreadsheet:

We use spreadsheets to

manage tables, prepare financial reports or calculate scores for an examination report sheet in the school. E.g. MSExcel, FoxPro, LOTUS 1-2-31

c)

Computer Graphic software: charts, pictures and several

This beautiful

makes it possible for the user to manipulate designs with the computer. E.g. COREL DRAW 10, ADOBE PhotoShop, ADOBE Illustrator, PRINTMASTER Gold Deluxe and so on.d)

Database:

This software allows the user

to enter data such as the names of students in a school with their ages and classes and enables the user to retrieve such information at a later date. UTILITY SOFTWARE This software takes care of the management and the security of the files inside the computer. We have Anti-virus packages like Dr Solomon Virus Scan, McAfee, NDD, Norton Utilities. There are also utility software that clears up the hard disks of nonsense files when the disk is nearly full.

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Central Processing Unit This is the main control unit of the computer. It can be said to be the brain of the computer or the heart and so on. Parts of the CPU The CPU consists of the control unit and the ALU (which stands for Arithmetic/Logic unit). These two work together using the program (instructions fed in by the programmer, you remember) and the data that are stored in the main memory to perform. Therefore the parts of the CPU include a) b) c) control unit; ALU and Main memory

Main Memory The main memory stores three items. These include:

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a)

the operating system e.g. Windows 95/98 or windows XP that directs and monitors the activities of the computer equipment;

b)

the application software that will direct the work that is to be done by the user whether it to type a letter or design a card;

c)

the data, which is currently being processed by the application software

What is Byte? What is Memory address? In the main memory, each location is called a byte. Just as a house on a street has a unique address that shows the location on the street, each byte in the main memory of a computer has an address that indicates its location in memory. The number that shows the location of a byte in memory is called a memory address Bit: is short form of binary digit. The computer basically understands only two things 1 and 0. This

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in Mathematics is called number base two or binary scale. Nibble: Byte: 4 bits make up a nibble 8 bits make up a byte or 2 nibbles make a byte 1024 bytes equal 1 kilobyte (KB) (However, this is often abbreviated to 1000 bytes, so we say that 1kB is equal to 1000 bytes instead of 1024 bytes) The size of main memory is normally measured in kilobytes. When memory exceeds 1000kB (1 million bytes), it is referred to in megabytes (MB). 1000MB (that is one billion bytes) then it is called Gigabyte. Types of memory1.

RAM This stands for Random Access Memory. This is volatile in that whenever there is a power outage, everything stored in the memory is wiped off. This is where the computer stores the program that it loads during booting (later on this course) and also2

the place that the computer temporarily stores the data that is being fed in, before you save the work. Saving is the act of transferring the work that you are doing to the hard disk where you can retrieve at a later time.2.

ROM:

This

stands

for

read-only

memory. This is made up of all the instructions that were stored in by the makers of the computer. These instructions enable the system (computer is also called system) to start up or boot, for example. ROM cannot be altered (changed) or modified like the RAM.3.

PROM: read-only

This stands for programmable memory. Here, you can be

allowed to program what you want the computer to do but once this is done, you cannot again change anything. Note that it is

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only in the PROM that this programming can be allowed not the ROM.4.

EPROM: EEPROM:

This

stands

for

Erasable

Programmable read-only memory5.

This stands for Electronically

Erasable Programmable read-only memory What is booting? This is the initial start-up procedure of the computer. When you put on the computer, it tests itself and loads the operating system into the main memory of the computer. When it is doing this, the computer is not ready for use yet and is said to be booting. Cold Booting This occurs when the computer is switched on with the plugs correctly wedged into the socket in the mains. As a general rule, you put on the CPU first before the monitor. When you finish with the computer, i.e. at shutdown, you put off the monitor first before the CPU.2

Warm Booting Warm booting means to reset the computer. In this case, one does not have to put off the computer before switching it on again. To warm boot, three keys on the keyboard have to be pressed together. These keys are Control (Ctrl) key, Alternate (Alt) key and the Delete key (Del).. It is suggested that using your left hands (for a right handed person) press CTRL and ALT keys together, while at the same time you use the right hand to hit the DEL key. When you do this, you are warm booting the computer. AUXILIARY STORAGE DEVICES These are devices that store data or the output from the computer for later use. Generally, we have the rigid and the removable auxiliary storage devices Types of Auxiliary Storage devices1.

Magnetic disk storage;2

2. 3.

Magnetic tape; Optical disks; e.g. CD-ROM (Compact diskread-only memory) ,CD-i(Compact diskinteractive), recordable) rewritable) , CD-R CD-RW (Compact (Compact diskdisk-

4. 5. 6.

solid-state devices; Mass storage devices and Special-purpose storage devices, e.g. smart cards and optical cards

Of these types of storage devices, we will discuss only the magnetic disk storage. It is the most widely used storage medium for all types of computers. Diskettes The removable type is called the diskette. Since they are thin and flexible, they are sometimes called floppy disks or simply, floppies. They are convenient, reliable and inexpensive. There are two sizes of diskettes: 3 floppy disk and 5 floppy.2

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Care of diskettes1. 2. 3. 4. They should be prevented from direct sunlight; Heavy objects should not be placed on top of diskettes; Do not expose diskettes to hot places or high temperatures; Avoid touching the magnetic medium with bare hands;

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5.

Do not press the diskettes with your biro pen or pencil when writing on the label. That explains why felt pens are recommended.

6. 7.

Avoid bringing diskettes close to magnets or magnetic materials; They should not be brought near dust, smoke or water

Hard Disks This type of magnetic disk storage is rigid and is fixed inside the system unit. Hard disk is completely sealed and therefore is less prone to damage. Example is Winchester disk, Western Digital disk, Maxtor disk and Seagate disk. The hard disk itself consists of round metal platters on which the data are stored and the readwrite head, which is used to access the data that is sought. The storage capacity of hard disks is measured gigabytes in megabytes is and more and recently of (that millions2

billions

characters) of storage. This is just like you have 60-leave or 80-leave notebooks that will store more notes than the 40-leave notebooks. We also have removable hard disks especially in some notebook computers and these are used to ensure higher security of the stored data. There are also hard cards. The hard card is a circuit board that has a hard disk built onto it. They provide an easy way to expand the storage capacity of a personal computer Protecting data stored on a disk Regardless of whether you are using floppy disk or hard disks, you must have to protect the data that you store on the disk from being lost. The disk storage is re-usable since the stored data may be overwritten and replaced by new ones. This is clearly a desirable feature because we are afforded the privilege of replacing or removing unwanted files. However, it also poses the problem and possibility of accidentally removing or replacing the2

file that we wanted to keep. Therefore, to protect programs and data stored on disks, we may:a)

Write-protect the diskette:This is done by using the write-protect notch that is located at the lower side of the diskette. So, to prevent writing to a diskette, you will have to move a plastic cover to open the window. If the writeprotect notch is closed however it means that the drive can write or copy something on the diskette. Once again, if the window is open, the drive will not write on the diskette or floppy disk.

b)

Back-up storage:

Another good

way to protect our programs or data stored on disks is by creating back-up storage. This simply means creating a copy of important programs and data on one diskette to another diskette. The

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diskette is equally a convenient medium that is used to back up the data stored on a hard disk of a personal computer. Today, we now have recordable and rewritable compact disks that can store the entire contents of a hard disk as a back-up storage. This is made possible by the use of CD-Writers. COMPUTER VIRUS A computer virus is a computer code or program that is capable of replicating itself and transferring itself from one computer system to another. Usually, virus can do such things as change programs or destroy data. They may even at times format the entire hard disk or blow up a monitor or disable a printer. When the host program (that is the program with the virus) is shared, the virus is spread. As the host program is copied to friends through diskettes, the INTERNET, bulletin boards and other usual3

channels, the virus is also copied along. It infects the software with which it comes in contact. They are not detected immediately. Some of them are like time bombs waiting for particular date to do their havoc. People who copy the host software are unaware that the virus exist because it is coded in such a way as to hide from computer users for weeks or even months. There are over 9000 viruses known and continue to increase by day and with the advent of the INTERNET even by the minute. Major kinds of computer virus include Boot sector viruses (that prevent the computer from booting properly), anti-CMOS viruses and Trojan horses. Examples of computer virus December 13 Black Jesus Howlen Croween B Jerusalem virus Polyboot A WM.opey97 Klein Holy Moseseek80 virus

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To neutralize the codes of the viruses, we use the antiviruses such as Dr Solomon AntiVirus kit, Norton AntiVirus, McAfee Virus Scan among others. Antiviruses have to be regularly updated if they are to be effective. HOW TO AVOID COMPUTER VIRUS These are some techniques to at least minimize viruses and their damaging effects: The computer should be warm booted when switching applications. Write-protect your diskettes when they are to be inserted into suspicious computer systems Always use Antivirus to scan any suspicious diskettes before opening any file inside them. In using the INTERNET and bulletin board service, open e-mail accounts with servers suspicious programs or

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that provide antivirus software that will scan all incoming mails. Do not open or download any e-mail attachments from unknown sources until they are scanned. Even when these tips are followed, they cannot be total guarantee that your system or diskette could be virus-free when you engage in swapping (that is copying software). There fore the best method is to perhaps avoid swapping. Use only registered and licensed software and avoid tolerating diskettes from unknown sources from being inserted into your system.

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NETWORK When two or more computers are connected together, they are said to form a network. For computers to see each other on a network, same set they of have rules, to follow the or commands

configurations called protocol Examples of protocols: a) b) FTP TCP/IP File transfer protocol Transfer control protocol/Internet Intranet protocol c) d) e) NetBEUI WAP HTTP British standard protocol Wireless Applications protocol hyper text transfer or

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protocol. Types of Network There are two major kinds of network based a) b) computers or campus Wide are Area in Network: In this type of network, computers connected together wide geographical or even area like different cities countries. on the geographical distribution of the computers: Local Area Network (LAN) and Wide Area Network (WAN) are connected together Local Area Network: This is when the within the same area such as building

The INTERNET is a good example of WAN.

What is Server?

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What is Client? Networking for When file is very advantageous as well as you you sharing are to of

resource sharing. computers have for each networked, buy them. All wouldnt printers separate

have to do is buy a single printer for all of them to share. Note that they have to have the same protocol, which is the set of rules in and a regulations governing the exchange of information network. Now, a server is the network control unit that is dedicated to handling the communicating needs of the other computers in a network. These other computers are referred to as clients. between computers

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Whatever

is

to to

be be

shared

among to

the the

computers in such a network, say, a printer has connected server. Using LAN, all the computers and the server can use the printer. In channels and a are cables network, very are communication Wires used, although essential.

wireless systems such as light beams, radio waves or carrier-connect radio are now prevalent. VSAT (very small aperture networks terminals) in both has largely and improved the efficiency of Wide Area Intranet INTERNET access. NETWORK TOPOLOGY Network topology or describes layout the of configuration physical

the equipment (such as computers and

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peripherals) network.

in

a

communications

Types a) star network b) bus network c) ring network Gateway: hardware users on resources network. Bridge: is a combination of hardware and software that is used to connect similar networks. Nodes: Devices connected to a network, such as terminals, printers or other computers are referred to as nodes. is and one on a combination software network a to of both allow the of that

access type

different

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Hub: This is a device that connects all the workstations or client computers in a network to the server. We have 9- port, 16-port hubs and so on.

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ADVANCED ESSAYS

1800 AD Jacquard's Punched Cards

1800 AD Jacquards Punched Cards In the early 1800s, a French silk weaver called Joseph-Marie Jacquard invented a way of automatically controlling the warp and weft threads on a silk loom by recording patterns of holes in a string of cards. In the years to come, variations on Jacquards punched cards would find a variety of uses, including representing the music to be played by automated pianos and the storing of programs for computers IBM 80-column punched card format. See also: Charles Babbages Analytical Engine & Herman Holleriths tabulating machines

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1890 AD Herman Hollerith's Tabulating Machines

It is often said that necessity isthe mother of invention, and this was certainly true in the case of the American census. Following the population trends established by previous surveys, it was estimated that the census of 1890 would be required to handle data from more than 62 million Americans. a

In addition to being prohibitively expensive, the

existing system of making tally marks in small squares on rolls of paper and then adding the marks together by hand was extremely time consuming. In fact it was determined that, if the system remained unchanged, there was no chance of collating the data from the 1890 census into any useful form until well after the 1900 census had taken place, by which time the 1890 data would be of little value.

The solution to this problem was developed during the 1880s by an American inventor

called Herman Hollerith, whose idea it was to use Jacquard's punched cards to represent the census data, and to then read and collate this data using an automatic machine. a

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While he was a lecturer at MIT,Hollerith developed a simple prototype which employed cards he punched using a tram conductor's ticket punch, where each card was intended to contain the data associated with a particular individual.

From this prototype, he evolveda mechanism that could read the presence or absence of holes in the cards by using springmounted nails that passed through the holes to make electrical connections.

Herman HollerithCopyright (c) 1997. Maxfield & Montrose Interactive Inc.

a

Hollerith's final system included an automatic electrical tabulating machine with a large

number of clock-like counters that accumulated the results. By means of switches, operators could instruct the machine to examine each card for certain characteristics, such as profession, marital status, number of children, and so on.

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a

When a card was detected that met thespecified criteria, an electrically controlled sorting mechanism could gather those cards into a separate container. Thus, for the first time it was possible to extract information such as the number of engineers living in a particular state who owned their own house and were married with two children. Although this may not tickle your fancy, having this capability was sufficient to drive the statisticians of the time into a frenzy of excitement and data collation. a

In addition to solving the censusproblem, Hollerith's machines proved themselves to be extremely useful for a wide variety of statistical applications, and some of the techniques they used were to be significant in the development of the digital computer. In February 1924, Hollerith's company changed its name to International Business Machines, or IBM. (See also Hollerith's punched cards.)

These notes are abstracted from the book Bebop BYTES Back (An Unconventional Guide to Computers) Copyright Information

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