CXC Information TechnologyUnit 1

Fundamentals of Hardware and Software1. State the functions of the basic components of all

computers and list examples where applicable. Control Unit, ALU, main memory/immediate access storage, backing store/disk storage, peripheral devices.

CPU

The Central Processing Unit (CPU) is the microchip brain of the computer. It contains the Arithmetic Logic Unit (ALU) and the Control Unit. It is connected to the Main Memory.

Control Unit is in charge of the CPU. The control unit executes the instructions of the program. The control unit only understands very simple instructions call machine code.

Arithmetic Logic Unit (ALU) works under the direction of the CPU and performs arithmetic and logic operations.

Main Memory, sometimes known as immediate access storage or primary storage, stores the program currently

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Main Memory

Arithmetic and Logic Unit

Control UnitInput Output

Backing Storage

being executed by the CPU and the data needed by the program. Data in main memory is lost when the computer is turned off.

Backing Store, sometimes known as the disk drive or secondary storage, stores programs and data not being used. Data stored on secondary storage devices is not lost when the computer is turned off.

Peripheral devices are devices externally connected to the computer such as the mouse, keyboard, printer and scanner.

2. Explain the functions and uses of primary storage devices and media. Bistable devices, PROM, EPROM, RAM, ROM, byte, kilobyte, bit, megabyte, gigabyte, terabyte, word, wordsize, address, location and address content.

Bistable:- A bistable circuit or flip-flop is a simple electronic circuit that remains in one of two stable states until it receives a pulse (logic 1 signal) through one of its inputs, upon which it switches, or `flips´, over to the other state. Because it is a two-state device, it can be used to store binary digits and is widely used in the integrated circuits used to build computers.

ROM (Read-Only Memory):- memory device in the form of an integrated circuit (chip), frequently used in microcomputers. ROM chips are loaded with data and programs during manufacture. They can be read but not written to by the computer. However, the contents of the chips are not lost

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Teaching Activity:A coin as an example of a bistable device.Ask all the students to stand. Now ask them to choose heads or tails, heads raise their hands. Flip a coin, those students who guessed wrong sit down. Repeat until only one student remains who wins the coin.

when the power is switched off. ROM is used to form a computer's permanent store of vital information, or of programs that must be readily available but protected from accidental or deliberate change by a user. For example, a programmable calculator will contain ROM to hold the instructions for performing the standard mathematical functions such as sin , cos and tan which never change.

PROM (Programmable Read-Only Memory):- A memory device in the form of an integrated circuit (chip) that can be programmed after manufacture to hold information permanently. PROM chips are empty of information when manufactured but can be programmed once.

EPROM (Erasable Programmable Read-Only Memory):- Computer memory device in the form of an integrated circuit (chip) that can record data and retain it indefinitely. The data can be erased by exposure to ultraviolet light, and new data recorded. EPROM can be programmed many times.

RAM (Random-Access Memory):- A memory device in the form of a collection of integrated circuits (chips), frequently used as the Main Memory in computers. RAM chips can be both read from and written to by the computer, but their contents are lost when the power is switched off. Many modern commercial programs require a great deal of RAM to work efficiently. The 64 megabytes (MB) of RAM with which most computers are sold with may not be enough: 64 MB is a minimum recommendation, and 128 or 256 MB, if you can afford it.

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Teaching Activity:Point to a book. Is this ROM, PROM or EPROM. (ROM)Point to the blackboard. Is this ROM, PROM or EPROM. (EPROM)Point to an exercise book. Is this ROM, PROM or EPROM. (PROM)

Bit:- Binary Digit. The smallest unit of data storage holds 1 or 0.

Byte:- Usually 8 bits. Bytes are a useful unit because 1 byte can store 1 character.

Word and wordsize:- A word is usually 4 Bytes or 32 bits. It is convenient for a computer to use a word to hold numbers. This is where the term 32-bit machine comes from.

Kilobyte:- Some people think this is a 1000 but in the world of computers a kilobyte is 1024 bytes. This is because 1024 is 210 or 2*2*2*2*2*2*2*2*2*2. Think about a kilobyte as 1024 characters or 10 pages of a typical book.

Megabyte:- 1024 Kilobytes or 1,048,576 bytes or 220. That is enough storage to hold 100 books full of characters.

Gigabyte:- 1024 Megabytes or 1,073,741,824 bytes or 230. That is a room full of books.

Terabyte:- 1024 Gigabytes or 1,099,511,627,776 or 240. That’s a whole lot of books.

Location, Address and Content.

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Teaching Activity:If books are available ask each student to work out the capacity of a book by counting the number of characters on a page and multiplying by the number of pages. Create a pile of books that contain 1.44Mbytes and contrast this with a floppy.Teacher Activity:Give an example of the contents of somewhere e.g. ‘The contents of my bedroom is a bed.’ Ask students to give the contents of their bedroom. Give an example of the location of a bedroom e.g.‘My bedroom is on the first floor at the back of the house.’Ask students to describe the location of their bedroom.

Give an example of the address of a bedroom e.g.‘Bedroom number 2, 25 Camp Street, Georgetown, GuyanaAsk students to give the address of their bedroom.

Location:- each word is located in memory. These are known as memory locations.

Address:- every memory location has an address so that it can be accessed.

Address content:- the contents of the memory location at the given address.

3. State and compare the characteristics and uses of secondary storage devices and media. Magnetic tape, floppy disk, micro-floppy disk, hard disk (fixed head, moving head, exchangeable), optical disks, Magneto optical disks, CD, DVD.

Hard Disk drive :- Magnetic, capacity ranges from 40Mb to 100’s of Gb but 10 to 30 Giga bytes is common. Most hard disk drives are moving head and fixed into the system unit.

ZIP Drives :- Magnetic, 100Mb or 250Mb capacity, removable/exchangeable. Expensive alternative to floppy disks.

Floppy Disk drive :- Magnetic, 1.44Mb capacity, removable/exchangeable. Slower and more unreliable than a hard disk drive but convenient for moving data from one computer to another. Watch out for viruses!

Micro-floppy disk:- A mini floppy disk sometimes found on laptop and palm top computers.

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CD-ROM (Compact Disk Read Only Memory) :- Optical, 650Mb capacity.

CD-R (Compact Disk Recordable) :- Allows you to record your own CD-ROM’s CD-RW (Compact Disk ReWritable) :- Uses a special Compact Disk that is reusable, but note that not all CD-ROM drives can read these special ReWritable CD’s.

DVD (Digital Versatile Disk) :- Optical, capacities vary but 4.7 Gb and 8.5 Gb are common.

Some devices use a combination of Magnetic and Optical techniques to store data these are Magneto-optical disks.

Common Backup Devices

A Backup is a copy of all the important files on your system in case your hard disk drive fails.

Tape Drive or Tape Streamer :- Magnetic, sequential device with very high storage capacities up to 100’s of Gigabytes. Similar to a music cassette or video tape. Common makes of tape include DAT, DLT, HP and EXABYTE.

CD-R and CD-RW are sometimes used as backup devices.

4. Explain the terms associated with backing storage devices and media. Read/write heads, sectors, tracks, buffers, cylinders, access time, sequential access, direct access.

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Teaching Activity:Ask students to look at the ‘How Multimedia Computers Work’ CD focus on the hard disk drive and CD-ROM.

Teaching TipHave a CD, CD-R, CD-RW and a tape to pass round. A music tape could be used if a DAT/DLT/Exabyte tape is not available

Platter :- Hard disk drives contain a number of platters or disks of magnetizable material.

Each platter on a hard disk is divided into tracks and sectors.

Track :- If a read/write head remains still as the platter spins the read/write head passes over a single track on the platter. The tracks are concentric circles on the platter.

Sector :- Each track is divided into many sectors.

Cylinder :- When the read/write heads remain still tracks on each platter can be accessed. This is a cylinder.

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Teaching Activity:Have an old disk drive available that details the number of sectors, track, platters and ask students to work out the capacity.

The speed of a hard disk drive depends on two main factors seek time and latency.

Seek time is the time it takes to move the read/write head to the correct track.Latency is the time that the read/write head has to wait for the correct sector to come round. Latency depends on how fast the disk is rotating.

Access time = Seek time + Latency time.

A typical disk drive has 16 heads, which means 8 platters.6,253 Tracks.63 Sectors per track.512 Bytes per sector, which means 512*63*6,253*16 = 3,227,148,288 bytes or approximately 3 Giga bytes.

Disk drives are direct access devices, sectors can be accessed in any order.

Magnetic tapes usually have 8 tracks allowing 1 byte to be stored across the tape. Tape drives are serial or sequential devices, bytes are accessed in order from the beginning to the end of the tape.

Buffer:- Disk drives have memory of their own. This allows the disk drive to accept data from the CPU faster than it can write it to the disk. Think of the buffer as a waiting area for data between the CPU and the disk drive.

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5. State the characteristics and uses of input devices and media. Optical mark reader (OMR), character readers (OCR, MICR), mouse, joystick, light-pen, touch terminals, voice data entry (VDE), voice response unit, pads and tablets, point of sales (POS), bar code, keyboard, key to disk, scanners.

Mark Sensing and Optical Character Recognition :- In mark sensing, marks are made in pencil on a specially designed form. The position of the mark is detected and converted into meaningful data.

For example.A form could have the following question:

Yes NoDo you like fish? < > < >

The person simply has to put a line through Yes or No to mark down their answer. A mark sense reader reads the answers directly into the computer. There is no keying in of data. Mark sensing is often used for multiple choice tests.

Optical Character Recognition (OCR) :- Similar to a mark sense reader as it scans data into the computer directly. However, it is not the position if the mark that gives the data to the computer. It is the shape of the mark that tells the computer what the characters and numbers are. OCR can be used to scan whole pages of text into a computer at once.

Magnetic Ink Character Recognition (MICR) :- Used on bank cheques. They have 14 different letters, including the digits 0 to 9. The letters are printed using magnetic ink along the bottom of the cheque, which can be read directly by the computer. When a customer buys something using a cheque, they fill in all the information - such as the name of the shop, the price of the goods and the customer’s signature. This information is then put on the cheque in magnetic ink. The completed cheque is then taken to the

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bank that uses a MICR reader. The cheque is then read into the computer.Data is not verified, and cheques can easily be damaged. However, input can be very fast - 2000 cheques can be read in a minute and is difficult to forge.

Mouse :- Mice can have two, or three buttons. Mice are used with a WIMP (Windows, Icons, Menus, Pointers) environment.

Joystick :- Used mainly for games. When the joystick is moved, the computer responds to these changes and moves the pointer on the screen accordingly.

Bar Codes and Light Pens :- Bar codes are read by the computer using a light pen or a laser scanner. They can be found in many supermarkets. The bar code is read by the pen or scanner. This information is used to identify the item - such as a can of coke. Most items now have a bar code on them. The information is scanned at the till which is connected to the computer. This is called a Point of Sale terminal (POS terminal).

A bar code contains: the country where the product came from, the company, the product, and a check digit. Once scanned, the information can be put onto the receipt showing full details of the item.

EPOS allows detailed information to be held within the system. It helps with stock keeping, re-ordering and marketing. Tills can be operated quicker so fewer staff are needed. Individual price tags are not needed, but this can make things harder for the customer who wants to compare individual prices.

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Teaching TipHave a bank cheque available to pass round for the students to look at.

Touch Screens :- A touch screen operates by touching the screen to select an option. They are commonly used for public information. For example, Airports have a touch screen information service point that provides information about flights, tourist sights etc.

Voice Data Entry (VDE) :- This is a useful, but undeveloped method for input. Everybody can talk but not everyone type at high speed. We use a microphone for input, and speakers for output.

Graphics Pad :- Drawing using the mouse or tracker ball is possible, but different to using a pen on paper. A Graphics pad allows you to use a pen, which is much more natural. The surface of the graphics pad is a thin membrane surface that registers the pen’s movements.

Keyboard :- The most common device for data input.

Key to disk :- Historically computers were expensive so data was not typed directly into the computer as we do today. Key to disk systems were used to input the data onto a disk which would then be read by the main computer.

Scanner :- Scanners are used to input text, diagrams and pictures into the computer. Text can now be recognized using OCR software, so the text scanned in can be converted to text ready for use by a word processor. Diagrams and pictures, when scanned into the computer, can be used by graphics or photo editing software.

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Teaching ActivityIf a scanner or digital camera is available allow students to experiment scanning in pictures and text. Students should use the images to produce an article for the school magazine.

Magnetic Stripe Cards :- A magnetic stripe is a small strip of magnetic tape sealed onto the surface of a plastic card. Banks, credit card companies, and telephone companies use them. The strip contains information such as the customer’s credit limit (if it were a credit card) or the amount of units left on the card (if it were a telephone card).

Sensors :- There are many types of sensors that are used to measure things like heat, or wind speed. Sensors could be used to monitor the temperature in a furnace.

6. Compare the characteristics and functions of output devices and media. Visual display unit (VDU); resolution, printers, character, line, page, impact, non-impact, plotters, voice, microfilm, permanent (hard copy), temporary copy (soft copy), speed, print quality, storage capacity, human readable, machine readable.

Monitors or VDU (Visual Display Unit) :- Most information can be displayed on the monitor.

A monitor can be high, medium, or low resolution. Resolution is measured in pixels. A pixel is a very small area of the screen. It can be thought of as a very small dot. These dots are used to make up a picture - similar to the dots which make up the pictures in newspapers.

High resolution can display 1024 by 768 pixels, or more. They are used for very detailed graphics work. The screen can be large and is often expensive.

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Teaching Activity:Input devices poster in word processing or DTP. Students work is small groups to produce a 1 page poster of input devices. Use of scanner and digital camera, if available, should be encouraged. Pictures of various input devices must be available. Computer Desktop Encyclopaedia is a good source. If possible print and display the best posters.

Medium resolution can display 800 by 600 pixels.

Low resolution can display 640 by 480 pixels- similar quality to a television set.

Printers

Character printers, now very old, print one character at a time like a typewriter.

Line printers, again old technology, form a complete line before printing. Chain printers are an example.

Page printers, modern printers that print a whole page at a time. Can be laser or inkjet printers.

Ink Jet Printer :- Non impact printers where ink is squirted out onto the paper to form the output.

Ink Jet printers are cheap to buy, but can be expensive to run - the ink needs replacing regularly, and the nozzles which squirt the ink can become blocked. However, they produce very good quality print, and can use colours.

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Teaching TipSet up three identical monitors with different resolution settings. Ask the students which they think is the ‘best’ setting.

Teaching Activity:Ask students to draw a circle in Paint. Use the Zoom feature to edit at the pixel level.

Laser Printer :- Page printer. Laser printers can print a wide variety of characters and graphics. Colour printers are also available. Quality is excellent.

Laser printers are very popular. They are flexible, very fast, and quiet. However, they are expensive.

Impact and non-impact. An impact printer works by impacting the shape of the character through a ribbon onto the paper. Dot Matrix printers are impact printers. Letters are formed by a grid, or matrix of 7 by 5 dots. They use a print head which has a grid of pins which are used to form letters when pressed against an ink ribbon. Dot matrix printers are cheap and reliable. They are used in small offices, and schools.

Hard copy. Printed output from the computer is called hard copy. Hard copy is usually human readable.

Soft copy. Output displayed on a screen.

Other output devices include:-

Voice synthesis :- Often used at airports for routine announcements of flights in different languages.

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Teaching Activity:If printers are available set up a race between a dotmatrix, laser and inkjet. Use a spreadsheet to produce a bar chart of pie chart comparing the speed of the printers.

Teaching Activity:Ask students to look at the ‘How Multimedia Computers Work’ CD focus on the laser printer.

Microfilm :- Now old technology.

7. Describe how data are stored and manipulated within the computer. Binary number, binary addition, ASCII, discrete and continuous data, parity, conversion of decimal to binary and binary to decimal. Representation of integers (positive and negative); sign and magnitude; two’s complement; characters; BCD representation.

The binary number system is a system of 1’s and 0’s To convert from binary to decimal use the sequence

128 64 32 16 8 4 2 1

To convert from binary to decimal write down the binary number under the sequence lined up to the rightE.g. 10010

128 64 32 16 8 4 2 11 0 0 1 0

and add up 1*16 + 0*8 + 0*4 + 1*2 + 0*1 16 + 0 + 0 + 2 + 0 = 18

Converting from decimal to binary is easy too E.g. Convert 89 to Binary

Write down the sequence128 64 32 16 8 4 2 1

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Teaching Activity:Having students do conversion on the board works well and gives them confidence.

Is the number (89) bigger than or equal to 128? No so write a 0 under the 128 in the sequence.Is the number (89) bigger than or equal to 64? Yes so write a 1 under the 64 in the sequence and take 64 off 89 leaving 25.Is the remaining number (25) bigger than or equal to 32? No so write a 0 under the 32 in the sequence.Is the remaining number (25) bigger than 16? Yes so write a 1 under the 16 in the sequence and take 16 off 25 leaving 9.Is the remaining number (9) bigger than or equal to 8? Yes so write a 1 under the 8 in the sequence and take 8 off 9 leaving 1.Is the remaining number (1) bigger than or equal to 4? No so write a 0 under the 4 in the sequence.Is the remaining number (1) bigger than or equal to 2? No so write a 0 under the 2 in the sequence.Is the remaining number (1) bigger than or equal to 1? Yes so write a 1 under the 1 in the sequence and take 1 off 1 leaving 0

So we have

128 64 32 16 8 4 2 11 0 1 1 0 0 1

How is Numerical Data Stored in the Computer

BCD :- Binary Coded Decimal is the simplest way of storing data in a computer. Each digit is given a binary code

decimal 0 is 0000decimal 1 is 0001decimal 2 is 0010

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!! !!!! !!

decimal 9 is 1001 2 4

so the number 24 would be stored as 0010 0100.

This isn’t very useful so sign and magnitude representation was developed.

Sign and Magnitude :- The first BIT of the number is the sign the remaining bit are the binary number so :-

00001110 is decimal 1410001110 is decimal –14

Sign and magnitude works well until we want to add numbers with different signs together.

This is not easy so the really clever computer boffins invented two’s complement.

Two’s Complement :- A really clever system for storing numeric data so that numbers with different signs can easily be added.

Here is how it works

For any binary number the negative of that number is represented by reversing the bits (1’s complement) and adding 1 (2’s complement)

Example

Decimal 12 is 00001100So to find how decimal –12 will be stored reverse the digits to get

11110011 (1’s complement)and add 1

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11110100 (2’s complement)

The really clever thing about two’s complement is that it makes maths easy for the computer.

7 – 3 is the same as 7 + (-3)

00000111 is decimal 711111101 is decimal –3

add them together00000100 which is 4

Characters are held in the computer using binary numbers according to the ASCII (American Standard Code for Information Interchange)

In ASCII ‘A’ is 65 or 1000001 in binary

The next letter ‘B’ is 66 or 1000010

and ‘C’ is 67 or 1000011

so‘Z’ is 90 or 1011010‘}’ is 125 or 1111101

Parity

When binary data is transmitted, for example over the Internet, errors can occur. Parity checking allows these errors to be detected and repaired. Consider sending the block of binary numbers

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Teaching TipGo through some examples on the board where the students suggest the numbers.

1 1 0 0 0 1 0 10 0 1 1 1 0 1 00 1 0 1 0 0 0 10 1 1 1 1 0 1 11 0 1 0 1 1 1 01 0 0 0 1 0 1 01 0 1 0 0 0 1 01 1 0 1 0 1 0 1

Parity can be Odd or Even. In Odd parity the number of 1’s in each row and in each column must be odd. To achieve this one extra row and one extra column is added to the data. If the number of 1’s in a row is even the extra data bit will be a 1 making the total for the row odd. If the number of 1’s in a row is odd the extra bit will be a 0 keeping the total for the row odd. The same procedure is applied to the columns.

Parity1 1 0 0 0 1 0 1 10 0 1 1 1 0 1 0 10 1 0 1 0 0 0 1 00 1 1 1 1 0 1 1 11 0 1 0 1 1 1 0 01 0 0 0 1 0 1 0 01 0 1 0 0 0 1 0 01 1 0 1 0 1 0 1 00 1 1 1 1 0 0 1 Parity

If the original data is corrupt in one bit the parity is wrong on one row and one column so the incorrect bit can be detected and automatically replaced.

Parity1 1 0 0 0 1 0 1 10 0 1 1 1 0 1 0 10 1 0 1 0 0 0 1 00 1 1 1 (0) 0 1 1 1 6 even1 0 1 0 1 1 1 0 01 0 0 0 1 0 1 0 01 0 1 0 0 0 1 0 01 1 0 1 0 1 0 1 00 1 1 1 1 0 0 1 Parity

4 even

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8. Distinguish between systems and applications programs. Operating system functions, batch processing systems, on line systems, disk formatting, file management, data transfer, resource management,

Computers do only one thing. They obey instruction. A set of instructions is called a program.

Hardware is the physical components of the computer.

Software is the programs.

There are two main types of software:-

System Software are the programs that run the computer. The operating system is the part of the system software. With out an operating system the computer is useless. Windows 98 is a common operating system.

The operating system manages the hardware resources of the computer such as the memory, disk drives, monitor and printer.

The operating system allows the user to manage their files by providing files and folders.

It provides an interface between the user and the computer.

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Teaching Activity:Work through an example on the board then choose a student to leave the room. Change a single digit. The student must check the parity to find and correct the data corruption.

Teaching Activity:Worksheet 1 Operating System.

There are 2 types of operating systems :-

a. On Line Systems allow you to sit at the computer and work.

b. Batch Processing System allows you prepare your program away from the computer and submit it the computer operator to be run.

Application Software are the programs that are used to do the work. MS Word, Excel, CorelDraw are all application software. It is important to choose the right application for the job.

UseWord processing for text manipulation.Spreadsheet for automatic calculation.Database for storing and manipulating data.Desk Top Publishing for page layout

9. Discuss the difference between generalised and specialised application packages. Application programs, custom written software, general-purpose software; specialised software package, customisation of general-purpose software.

Application Software are the programs that are used to do the work. MS Word, Excel, CorelDraw are all application software. It is important to choose the right application for the job. There are 2 types of application software :-

General Purpose applications can be used for different jobs. A word processing package can be used to write letters, reports, stories or adverts. It is possible to customise

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general-purpose applications using templates. For example a company might create a letter head template document that includes the company’s address and logo to be used for all letters.

Specialized applications can only be used for one job. A payroll package can only be used to calculate payroll.

Software programs can either be :-

Bought Off The Shelf from companies like Microsoft or Corel. This is usually general-purpose applications.orCustom written software where the company writes the program for itself using a programming language like Pascal or Qbasic.

10. Distinguish between types of user interface. Command driven, menu driven, HELP facilities, pull-down and pop-up menus, icons. Hardware: touch screens, pivoted monitors, antiglare screen.

Command line and Text based system. Interaction with the computer is with lines of text. You type in a command and the computer responds.

An example of a text based system

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Welcome to the Exchange Bureau 1) Euro 2) Japanese yen 3) American dollars 4) Russian roubles Please select a currency for conversion1, 2, 3 or 4 _

Teaching Activity:Set up a simple QBASIC program, such as the currency exchange program, and allow student try out the program.

Graphical User Interface (GUI). Uses pictures and a pointing device as the means of interacting with the computer. Windows 98 is an example of a GUI.

A GUI usually includes WIMP.

Windows, Icons, Menus, Pointer

All good interfaces have help facilities to assist you, look for a help menu in a GUI or type ‘HELP’ in on the command line.

Hardware is also part of the Human Computer Interface and consideration might be given to touch screens, pivoted monitors that can be adjusted for easy viewing and antiglare screens which can reduce reflections from the monitor.

11. Describe and apply appropriate file management techniques. Directories, naming of files, labelling of diskettes, storage of files on diskettes, user back-up; user check point.

File.A collection of data or a program stored in the computers external storage, on the hard disk drive.

Files are used to contain word processing documents, spreadsheets, databases, pictures and presentations. They also contain programs such as MS-Paint, CorelDraw or MS-Word.

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Teaching Activity:‘Help’ races. Ask the students to answer prepared questions using help and quickly as possible. For example ‘What tool is used to playback animation files.’ Checkout your questions on the systems to be used beforehand because help facilities may vary.

A computer may have many thousands of files so it is important that files always have meaningful names. ‘Register 3B’ is a good filename, ‘My Stuff’ is not.

To keep all these files in order the operating system uses directories or folders.

Directory or FolderA directory or folder, they are same, is a container in which to store files that belong together. For example all the files for Windows 98 are stored in a folder called Windows. Users normally keep their files in a folder called MyDocuments.

To help organise files further the operating system allows a folder to contain other folders. You might create folders to contain your English essays and another to contain your maths homework.

Diskettes are useful to students for storing small numbers of files and folders. Diskettes should be clearly labelled identifying the contents of the diskette.

Back-ups. A floppy diskette, CD-Recordable, CD-ReWritable or magnetic tape can be used as a backup device. A backup is a copy of important files kept in different location. Users should make copies of all their important files regularly, perhaps once or twice a week. Many people keep several copies e.g. a copy of last week’s files on one floppy and a copy of the files from a week before that on another.

12. Use the appropriate operating system functions to

Create a directory/folder. Produce a directory listing of files. Prepare a diskette to store data. Copy single files from one diskette to another.

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Teaching Activity:Worksheet 2 Floppy disks.

Create a backup copy of a diskette. Delete unwanted files.

13. Recognise and use the terms commonly associated with data communication. Point-to-point and broadcast transmission computer network, modem, bandwidth, simplex, duplex, half duplex protocol, local area network, wide area network, up-load, down-load, e-mail, bulletin board, data transfer mode, voice band.

Local Area Networks (LAN) :- Where the computers to be connected are quite close to one another then a LAN may be used. Resources like printers, plotters etc. may be shared. Local Area Networks are useful when connecting computers inside the same building. Small business in particular uses them to share resources, scanners, plotters and laser printers.

Wide Area Network (WAN) :- When computers are geographically separate then a WAN is appropriate. Wide Area Networks are useful for organisations that have department or branches in different buildings or locations.

It isn't always the case that data can be transmitted over a committed network. For remote sites the transmission of data may be over the public telephone network.

Modem :- The main item needed to communicate over the telephone network is the modem. Because computers use digital ones and zeros these must be converted to sound for use on a telephone. This is known as Adulation and is done with a modulator. At the other end the sound has to be

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Teaching Activity:Worksheet 3 Files Management.

converted back to digital ones and zeros that is Äodulation and is done with a demodulator. Hence MODEM (MOdulator DEModulator). Card Modem/Internal Modem is internal to the computer and the telephone cable is connected directly to the computer. The speed of communication is commonly called the bandwidth. For a modern modem the bandwidth is 56 kbps (kilo bits per second).

Protocol :- A protocol is the rules that computers agree to use when communicating with each other. They are like languages; to successfully communicate computers must use the same protocol.

Point-to-Point Communication :- Used when two computers are communicating with each other over a network.

Broadcast Communication :- Sometimes one computer needs to communicate the same message to many computers on the network. The message is broadcast to all computers on the network.

Simplex :- Transmission is in one direction only. Shops may use this to transmit to the head office sales figures.

Half duplex :- Transmission is bi directional but only one direction at a time.

Full duplex :- Transmission is either way at anytime.

Down-load :- Down-loading refers to the process of copying data from a remote computer. For example you down-load a World Wide Web page in order for you to view it.

Up-load :- Up-load is far less common and refers to the process of copying data to a remote computer.

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Teaching Activity:If you have a network allow the students to ‘chat’.

Electronic Mail (e-mail) :- Messages sent electronically from computer to computer over a network.

Bulletin Boards :- Like a regular bulletin board but stores and displays electronic messages rather than paper messages.

Voice Band :- Networks can be used to transmit all types of data including images and speech. When a network is used to transmit speech, e.g. Internet phone calls, this is the voice band.

14. Detect and rectify low-level problems with the computer hardware. Loose interfacing cables, improperly adjusted monitor controls, changing ribbons/cartridges.

Trouble Shooting Procedures for all Equipment.

There are some problems that can occur with any electrical or electronic equipment. In general these problems can be easily checked for and rectified.

Check the power supply socket. Plug in a device that you know is working such as a lamp.

Check the plug connections and fuse. It is important that the correct value fuse is installed and that the earth is connected.

Check all other connections. Many computer connection cables are fitted with clips or screws that ensure the cable is correctly seated. A visual inspection of the sockets should also be made. Connectors are either male or female, male sockets have pins and female sockets have holes. The pins in a socket can easily be broken but it is important to note that some cable connections do not require all the pins and it may look as if pins are missing. The most common fault on

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cable connections is that one or more pins become bent and no longer fit into the holes.

Make sure that everything is turned on.

If these simple measures fail to solve the problem further investigation is required, as a component failure may have occurred.

The monitor is not a users serviceable component. Very high voltages are generated in the monitor and are stored even after the monitor is turned off. There are, however, some checks that can be made without opening the monitor.

Check the power. Most monitors have a light to indicate they are turned on.

Check the brightness is turned up. This is common fault the brightness accidentally gets turned down until nothing is displayed on the screen.

Modern monitors have an energy saving feature. The screen automatically shuts down if the picture remains constant for a period of time. It automatically reactivates when the picture changes. Energy saving mode is usually indicated by the green power on light changing to red. This is sometimes known as standby mode.

Printers come in all shapes and sizes but they have common problems.

The simplest printer error is that the printer is offline. This means it is not ready to receive instructions from the computer. A pause or online button and associated light indicate if the printer is online or offline.

One or more covers are open. As a safety measure printers will not operate until all the covers are closed.

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Paper jams. Many printers now automatically detect paper jams. Some even go as far to indicate where the paper is jammed. Often the jam can be easily removed. If this is not possible refer to the manual, which will have a section on clearing paper jams.

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Teaching Activity:Set up some problems for small groups of students to diagnose. Problems that might be introduced.

No power to socket (switch off). Printer not turned on. Monitor not plugged into system unit. Mouse poorly connected. Monitor brightness turned down. No ribbon in printer. Monitor connected to another computer. Keyboard connected to another computer.