Computer Input and output devices

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Form 3 Computer Studies

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An Overview of Input and Output Devices

Input, Output and Secondary Storage Devices are collectively known as peripherals

The processor or Central Processing Unit (CPU) makes all the calculations of the computer. In order for a process to be possible we need to feed in data to the computer through the input devices. The computer will then process the data according to a particular program and finally deliver information through the output devices. If the information produced needs to be stored for the future, we will store this into a secondary storage peripheral device.

Input

Device

Computer

Output

Device

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Form 3 Computer Studies << Input Devices >>

Input devices are all those hardware equipment that are used to enter data into the computer.

Keyboard

This is the most common and widely used input device. There are different types of keyboards but the QWERTY keyboard is the most widely used. Apart from the normal alphabetical keys, the keyboard has:

- A Numeric Keypad

- Navigation Keys - Function Keys

Function keys change function used according to the application being used.

Mouse or Trackball

The second most commonly used input device is the mouse. The mouse helps the user to point and access items on the computer. Its main function is to control the cursor or pointer on the computer’s screen. The mouse can have 2 or 3 buttons, used according to the software application being used. Today, most mice also have a scroll wheel which is used mainly to scroll through documents.

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The trackball has the same basic functions of the mouse. The only difference is that the trackball is stationary and one doesn’t need to move it on a mouse pad.

In order to navigate with the pointer, the user must move a ball situated at the top of the device. Similar to the mouse, the trackball has 2 or 3 buttons used to select items from the screen.

Touchpad

This is a small sensitive pad used on portable computers (laptops).

The touch pad is used as a pointing device. The pointer is moved on screen by touching the touch pad with the finger. Tapping on the touch pad will give the same results as when using the mouse buttons. The touchpad is particularly useful for persons with disability whom can have limitations in moving their hand.

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Advantages Disadvantages

- Relatively inexpensive - Very little finger movement

needed to reach buttons

- When gripped too tightly can cause muscle strain - Uses more desk space than

other pointing devices - Must be cleaned regularly

- Uses less desk space than mouse

- Requires less arm and hand movement than mouse

- Wrist is bent during use - More finger movement

needed to reach buttons than with other pointing devices

- Small footprint - Least prone to dust

- Places more stress on index finger then other pointing devices do - Small active area makes

precise cursor control difficult

Scanner

The scanner is a device that transfers printed text and images to a computer. Today, most home users have a scanner connected to their computers. These are generally called flatbed (others less common such as barcode readers are called handhelds). The scanner alone is not enough to capture the data and transform it to a format that can be understood by the computer.

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In fact, one needs a number of software:

• Driver Software – Used to control the scanner hardware. • Photo Editing Software – Used to edit scanned photos

before being stored, printed or used in projects or websites.

• Optical Character Recognition Software (OCR) – When a printed document is scanned, normally this is stored as an image and thus the OCR is used to convert this picture to word processing format for editing.

Joystick

This device is well known with young people as it is mainly used for playing computer games.

As the name implies, it is like a stick connected to a platform, which can be moved in all directions.

These movements in turn will move something on screen depending on the game. Usually joysticks have buttons also called triggers.

Barcode Reader

When we buy products from shops we usually see small labels containing white and black stripes called barcodes. These labels contain information on the product. In order to read this information, one must pass the barcode in front of

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Optical Mark Reader

This device reads marks in predetermined places on specially prepared cards. These are usually used in multiple-choice questions.

The student will have to fill a space with a pencil, usually HB. The filled examination paper is then inserted into the OMR so as to enable it to read the answers marked.

Magnetic Ink Character Reader (MICR)

This system uses special ink to write numbers with coded magnetic ink. This special ink contains the written numbers magnetically. This system is widely used on cheques issued by banks. The MICR is much faster than OCR or other methods when reading codes and thus identifying cheques. 1 2 3 4 Federal Reserve District, 2 digits: 01 to 12 Branch / City Designation & Clearing

Bank Number Parity Check Digit (for reading error control)

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Graphics Table

Professionals, such as draftsmen and engineers, usually use this input device. It is used to speed up their drawing work. The device consists of a hand held operated device (similar to a pen) used to trace diagrams placed on a digitised table. The drawing will then be transferred to the computer.

Pen

Pens are used on hand held computers such as PDA’s (Personal Data Assistant). These hand held computers have a special sensitive screen.

When the user touches the screen it will interact with the computer

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Summary of Input Devices

Input Device Advantages Disadvantages

Keyboard Typists can use with ease Relatively slow

Mouse No typing skills are required At times can be tricky to use Light Pen No typing skills are required Needs much software to make

it versatile Bar Code Reader Quick and easy entry of data

under non-ideal conditions

Needs specialized software

OCR Can be programmed to read

text and neat handwriting

Elaborate hardware and software required, needs training

Mark Reader Fast input Elaborate hardware and

software required

MICR High volume, very reliable Only 14 characters are

represented

Joystick Easier than keyboard Special interface needed

Digital camera Easy image capture Still relatively costly Graphics Tablet Enables operator to enter

pictures

Slow

Speech Reader No hands needed Limited vocabulary

Touch Screen Easy operation

Intuitive

Needs specialised hardware and software

Hand Held Terminals Can have add-ons for sophisticated operations

Relatively slow

Scanner No artistic performance

required

High quality graphics require large amounts of disk space

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< < Output Devices >>

After processing the inputted data, the computer will give its output. This output can be in two different formats:

• Softcopy – Visual (monitor) or Sound (speakers)

• Hardcopy – Output on a tangible (something you can touch) such as a printer printout.

INPUT

PROCESS

OUTPUT as

Softcopy

OUTPUT as

Hardcopy

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Monitor or Visual Display Unit (VDU)

The monitor is the most common type of output device and is also called Visual Display Unit (VDU).

1. Monochrome – This type of display uses only one type of colour or a greyscale

2. Colour – This type of display uses more than one type of colour and is generally called RGB monitors. The RGB stand for Red, Green and Blue and a combination of these colours are used to display the image on the monitor. Colour monitors can display range from 16 to 16.7 million colours.

Resolution

This term refers to the clarity or sharpness of a printout or display screen. The more pixels there are per square inch, the better and greater the resolution.

Visual Display Units

1

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One can find different standards for monitors. They support different colour depths (number of colours it supports). The most common standards for monitors are:

1. VGA (Video Graphics Array) mode appeared in 1987. It offered a resolution of 720x400 in text mode and a resolution of 640 by 480 (640x480) in 16-colour graphics mode. It also offered a resolution of 1024 x 768.

The VGA quickly became the baseline display mode for PCs.

2. SVGA (Super Video Graphics Array) is a graphics mode which can display 256 colours at resolutions of 640x200, 640x350 and 640x480. SVGA can also display higher definitions such as 800x600 or 1024x768 by using fewer colors.

3. XGA (eXtended Graphics Array). is an IBM display standard introduced in 1990. Today, it is the most common appellation of the 1024 × 768 pixels display resolution, but the official definition is broader than that. It was not a new and improved replacement for Super VGA, but rather became one particular subset of the broad range of capabilities covered under the "Super VGA" umbrella.

The initial version of XGA expanded upon IBM's VGA, adding support for two resolutions:

• 800 × 600 pixels with high color (16 bits per pixel, i.e. 65,536 colors). • 1024 × 768 pixels with a palette of 256 colors (8 bits per pixel)

The Different Types of Monitors

The different types of monitors are:

Cathode Ray Tube (CRT) – uses the same technology as used in television sets.

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Liquid Display Unit / Liquid Crystal Display (LCD) – we usually find this installed in laptops and handheld computers. The technology used is different from that of the CRT. LCD uses tiny capsules filled with liquid crystals. When the molecules of the liquid are subjected to an electric field, the liquid crystals align and light reflects off them.

Without the field, their alignment reverts to its original, non-reflecting arrangement, so the elements appear dark.

Combinations of LCD’s are arranged to form patterns of reflected light that spell out numbers, symbols or letters.

TFT (Thin Film Transistor) is a variant of LCD which uses thin film

transistor technology to improve image quality.

Summary of Video Glossary

CRT Cathode ray tube (monitor)

VDU Video display unit (monitor)

LCD Liquid crystal display – as available on hand held games and potables Pixel The smallest area on a screen, seen closely as a tiny dot

14” 15” 17” 21” This is the length measured in inches (1 inch = 2.54cm) of the screen measured diagonally, that across two corners.

VGA Video graphics array, this provided,

1. Introduced analogue monitors to the computer system; that is colour was no longer restricted to fixed colours but allowed different hues and colour blending.

2. Graphics resolution of 1024 x 768 pixels 3. Allows 256 colours

SVGA Super Video Graphics Array

As above but allows 16.7 million colour hues Bit map Computer memory that represents a video image

Side NOTE: A terminal is an integration of a VDU with a keyboard. There are two types of terminals, namely INTELLIGENT TERMINLAS (having a CPU) AND DUMB TERMINALS (no CPU)

- Intelligent terminals can do some local processing of data and then communicate with a main computer just to relay the results

- In a dumb terminal, all processing must be done through the main computing system Printers

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Printers are output devices that transfer the output of the computer on paper (hardcopy). The printers can be divided into two categories Impact and Non-Impact:

• Impact – refers to all those printers whose printing heads touch the paper. An example is the Dot matrix printer.

• Non-Impact – are all those printers whose printing heads do not touch the paper. An example is a Laser or an Ink-Jet printer.

The following is a list of the different types of printers that exist:

Daisy Wheel Printers

This type of printer is rarely used any more since new printer technology, which is more efficient and economic, has been discovered. The principle of this type of printer is that number and letter are each situated on metal leafs as shown.

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Line Printers

As the name suggests these type of printers will print one whole document line at one go. There are two basic types of line printers:

1. Barrel Printers – This printer has a number of disks each containing all the letters and numbers. These disks are situated one near each other on a shaft and can rotate

independently from each other. Lines are written by revolving each disk in the correct position in order to form a complete line. A row of hammers will strike the ribbon and papers.

2. Chain Printers – All the alphabet and numbers are imprinted on a chain. In order to write on paper, a hammer will strike the right characters to print.

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Dot Matrix Printers

Dot matrix printers are categorised as character printers because they write one character at a time. The printing head is made up of several pins, which form a column. The printing head is attached to a belt which moves it from side to side along the width of the paper and at the same time the paper is rolled up by means of a roller. In order to write, the head pins are fired with the aid of an electro magnet, which hit the ribbon and paper.

Inkjet Printers

These types of printers are the most popular nowadays. It is basically what most home users have today. These printers have good resolution, are silent and for small amount of printing are not particularly expensive. These printers are called page printers.

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In the inkjet printing mechanism, the print head has several tiny nozzles, also called jets. As the paper moves past the print head, the nozzles spray ink onto it, forming the characters and images.

Laser Printers

Laser printers offer the best quality in terms of printout quality and resolution. On the other hand they are the most expensive to run. Laser printers are called page printers since they print one page at a go. The laser printer uses a laser beam, a drum and a toner.

Summary of Printer Classification

Printer Classification

Printers can be subdivided into four groups

CHARACTER LINE GRAPHICS PAGE

Prints character at a time

Prints a whole line at a time

Printers used for graphics such as CAD

Prints a whole page at a time

Printer Glossary

CPS characters per second (how many characters it is able to print in 1 second) NLQ near letter quality (very good print)

Draft Mode lowest printable resolution, it is also the quickest but not the best output, it is usually used for spell checking before the actual print

DPI dots per inch, this gives the resolution of the print, the higher the dpi the higher the resolution – more clear

Resident available on board (the printer) usually fonts or buffer memory Scalable can be set in different sizes.

Example: a

a

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Example: Tahoma, Times New Roman, Arial

Spooling A printer works relatively very slow when compared to a CPU. In order to free the CPU to attend to other tasks during printing, the printing job (file) is temporarily stored on disk, tape, or memory. The printer will then receive the file to print chunk by chunk – enough to keep it busy. This compensates for slow operating speeds of some peripheral devices. When spooling is to a printer’s memory, this is also known as memory buffer.

Memory buffer Printers have memory buffers to speed up their operation. Printing speeds are very slow compared to computer speeds and the printing job is spooled to a printer’s memory buffer. This is usually in the region of 10k to 50k RAM on small office printers. The computer downloads quickly in the fraction of a second the printing job to buffer memory. When the data in the buffer is exhausted, the next chunk of printing data is downloaded again by the computer in a split second. Sophisticated printers use large memory buffers and buffer area may be split into two separate memory areas.

Side NOTE:

On-line or Off-line

A peripheral device may be off-line or on-line

ON-LINE: refers to when a peripheral device is under the control of the CPU i.e. connected to the computer and usable

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The plotter uses pens to write on paper and is usually used for engineering drawings. There are two types of plotters:

1. Flatbed Plotter – This uses a flat paper which is fixed, and pens (or styluses) that move on it draw the required design.

2. Drum Plotter – Here the paper moves along a drum vertically while pens move side to side horizontally.

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Summary of Output Devices

Output Device Advantages Disadvantages

Dot Matrix Printer Versatile graphics and text, cheap

Average quality, slow speed

Daisywheel Printer Letter quality print Very slow, no graphics

Chain Printer Fast No graphics

Line Printer Can cope with high volumes Very noisy, average quality

Thermal Printer Quiet Special paper needed

Ink – Jet Printer Very quiet Ink smears occasionally

Laser Printer High quality, fast Expensive to run

Flatbed Plotter Large paper handling capabilities

Very expensive

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Vector and Raster

Vector – Is a line calculated in two dimensions and is

defined by its end points, which are x-y coordinates on a grid. Thus pictures are

composed of mathematically-defined geometric shapes

such as points, lines, arcs and other geometric figures.

If the picture or diagram is enlarged, it does not affect

the quality. Vectors are best used where high

contrast and colour is needed such as the design of

logos and geographical maps

Vector images have many advantages, but the primary disadvantage is that they're unsuitable for

producing photo-realistic imagery. Vector images are

usually made up of solid areas of colour or

gradients, but they cannot depict the continuous subtle tones of a photograph.

Raster – The picture image is created using a complex series of dots or pixels.

Raster stores the colour of each pixel in memory, and thus one needs a lot more memory than if using vector. Thus the overall picture will occupy more memory on the storage media. Raster pictures can be enlarged but they tend to lose quality. Raster images are also known as bitmap

images. These type of images use bits (1 or 0)

to describe each pixel’s attributes such as colour. The quality of a raster image depends entirely on the image resolution.

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These devices are used to produce sound from the computer system. The soundcard is a card installed in the tower case of the computer. Its role is to convert the signal coming out of the computer to a format that can be reproduced by the external speakers.

Computer Categories

Special Purpose (Dedicated) Computers: These are built to solve only one particular task. VCR and Optical recorders/players, Auto-pilot, Automatic Washing Machines, Mobile Phones, GPS, etc. will have an embedded computer to control them. The program for these computers is normally ‘hard coded’ that is built in the machine’s ROM (Read Only Memory).

Embedded systems controlling common appliances are one form of dedicated computers – they have a CPU, Input Output devices, software stored in ROM and some RAM as workspace.

General Purpose Computers: On the other hand, these can perform more than one

task provided that the correct instructions are loaded in the computer, therefore depending on what PROGRAM we load, the computer may act differently.

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Secondary storage devices cannot be classified under input or output devices. These devices are used to store data for later use.

Secondary storage devices can be categorised in 3 main groups:

1. Magnetic 2. Optical 3. Electronic

1. Magnetic Storage

Magnetic storage devices store the data on a magnetic layer. Examples of such devices are: a. Floppy Disk

b. Hard Disk c. Magnetic Tape

The technology used is very simple to understand. The magnetic layer is magnetised when there is a binary 1 and left un-magnetised when there is a binary 0.

Floppy Disk

Floppy disks store small amount of data typically not larger than 1.44MB. These small diskettes are used mainly to transport small files from one computer to another.

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The construction of the floppy is basically a plastic disk coated with magnetic material, enclosed in a PVC jacket to protect the magnetic material.

In order to write data to a floppy this must be first formatted. This procedure involves the creation of sectors and tracks. On the diskette, data is recorded on closed concentric rings (tracks).

Each track is divided into sectors. These are invisible wedged-shaped sections used by the computer for storage reference purposes.

Label

Hard Plastic Jacket Data Access Area

Metal protective plate (shutter) that moves aside (in disk drives) to expose data access are on disk

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Write Protection notch. The notch in this diagram shows that the floppy disk is not write protected.

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Hard Disks

As the name implies, hard disks are built with metal or glass platters covered with a substance that allows data to be held in the form of magnetised spots. Today hard disks are composed of more than one disk (also named as platter), which are stacked on each other. This technology gives the possibility of having large storage capacity. Typically computer systems today have an 80GB (or more) hard disk capacity.

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Magnetic Tape

This type of storage media is used in large computers where large amounts of data are stored. The tape is made up of a thin plastic tape having horizontal running tracks and vertical frames. The data to be stored is divided into:

a. The Header – Including file name and number of blocks b. Block – of data separated by inter block gaps

c. Trailer – containing number of blocks, to be used as cross reference with the header

Examples – Reel to Reel tape drive and Cassette Tape drive

Magnetic tape is ideally suited to store a list of records whose sequential order is sorted for later processing. Payroll systems and record updating is ideal for tape. A sorted tape can be used to issue pay cheques, update a list of customers etc.

Protection of Magnetic Storage

1. Do not put media in areas where magnetic field is present 2. Do not bend (Floppy Disks and Tape)

3. Do not store in high temperatures and / or in humid areas 4. Do not store in dusty environment

2. Optical Storage

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Form 3 Computer Studies Re adi ng Dat a Re adi ng “1” The lase r beams reflects off the smooth surface, which is interpreted as a 1 bit.

Reading “0”

The laser beam enters a pit and is not reflected, which is interpreted as a 0 bit.

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CD-R

CR-R which stands for Compact Disk- Recordable is a CD format that allows users to use a CD-R drive to write data, only once, onto a specially manufactured disk that can then be read by a standard CD-Rom drive.

CD-RW

CD-RW stands for Compact Disk – Rewritable. This type of media allows users to copy and erase data. Thus, this disk can be used over and over again.

DVD-Rom

DVD-Rom stands for Digital Video Disk or Digital Versatile Disk. This optical disk looks like a normal CD but in fact, it can store much more data than a CD

The following is a list of the most common DVD types with their respective capacities:

a. Single Sided / Single layer – 4.7Gb b. Single Sided / Double layer – 8.5Gb c. Double Sided / Single layer – 9.4Gb

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Electronic memory is the latest technology in secondary storage media. This is also referred to as Flash memory.

Flash memory is non-volatile solid-state computer memory storage that can be electrically erased and reprogrammed. It is a technology that is primarily used in memory cards and USB flash drives for general storage and transfer of data between computers and other digital products. It is a specific type of EEPROM (Electrically Erasable Programmable Read-Only Memory)

This type of memory media has no mechanical moving parts and thus it offers some advantages when compared to the other type of media.

Advantages: 1. Very small

2. Does not consume a lot of energy in order to function 3. Noiseless

4. Limited heat emission 5. Portable

Disadvantages:

1. Limited amount of memory capacity when compared to the other type of media (Currently big advancements are being made and the maximum capacity of this media is 60GB).

Because of their small size and big capacity, electronic memory is suitable to be used in portable devices. Today electronic memory is being used in Digital cameras, Mp3 Players, PDAs, Mobile phones and Laptops.

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Data Access Methods

We have two types of data access methods: a. Serial Access: - Cassette tape

- Tape Stream

b. Random (Direct) Access: - Floppy Disk

- Hard Disk

- Zip Disk - CD-Rom - DVD

- Flash Memory

Serial Access VS Random Access

Imagine one has a thousand records stored on a secondary storage device and one needs to access the 543rd record. In serial access, one has to access the preceding 542 records before homing in on to the 543rd_record.

On the other hand, in random (direct) access, one is given the possibility to go directly to the particular record required.

Serial Access Method

Serial access is where the items are read, one at a time, from the physical start of the file, in the order in which they are stored.

Data is stored on tape in Binary Coded Decimal Format. A tape is made up of horizontally running tracks and vertical frames. When a file is stored on tape, the program is divided into:

a. a file header (including the file name and number of blocks)

b. number of blocks (of a fixed number of records), each separated by inter-block gaps c. a trailer (with the number of blocks for cross checking with the program header)

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In serial access methods, as a means of security, parity checking is used. This is a means to check tape data integrity. Horizontal parity utilises a tape track for checking whilst Vertical parity uses a frame for parity checking. Both can be used for optimum integrity and error correction.

There are two types of parity systems – Odd and Even parity. In even parity, the tape drive ensures that both horizontally and vertically, there is an even number of 1’s. This system works similarly for odd parity. The only difference is that the 0’s are used instead of 1’s.

An even parity bit is set to 1 if the number of ones in a given set of bits is odd (making the total

number of ones, including the parity bit, even).

An odd parity bit is set to 1 if the number of ones in a given set of bits is even (making the total

number of ones, including the parity bit, odd).

Parity Bit Summary

- Even Parity

a. Set to 1 if number of 1’s is odd b. Set to 0 if number of 1’s is even

- Odd Parity

a. Set to 1 if number of 1’s is even b. Set to 0 if number of 1’s is odd

Transmission sent using odd parity:

a. A wants to transmit: 1001 A computes parity bit value: (1^0^0^1) = 1 b. A adds parity bit and sends: 10011

c. B receives: 10011

d. B computes overall parity: 1^0^0^1^1 = 1

e. B reports correct transmission after observing expected odd result.

This mechanism enables the detection of single bit errors, because if one bit gets flipped due to line noise, there will be an incorrect number of ones in the received data. In the two examples above, B's calculated parity value matches the parity bit in its received value, indicating there are no single bit errors. Consider the following example with a transmission error in the second bit:

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Transmission sent using even parity:

a. A wants to transmit: 1001

b. A computes parity bit value: 1^0^0^1 = 0

c. A adds parity bit and sends: 10010 *** TRANSMISSION ERROR *** d. B receives: 11010 B computes overall parity: 1^1^0^1^0 = 1

e. B reports incorrect transmission after observing unexpected odd result.

B's calculated parity value (1) does not match the parity bit (0) in its received value, indicating the bit error.

Even Parity Example

1 0 0 0 1 0 0 1 0 1 Even Parity Track 1 1 1 1 1 1 1 1 1 1 T 1 1 1 1 1 1 1 1 1 1 R 0 0 0 0 0 1 1 0 0 0 A 0 0 0 0 0 0 1 0 0 1 C 0 0 0 0 0 0 1 0 0 1 K 0 1 1 1 0 1 0 1 1 0 S 1 0 0 1 1 0 0 1 0 0 0 1 1 0 0 0 1 1 1 1

The diagram above shows the logical file structure on a tape (long pieces of plastic ribbon coated with magnetic material). Parity checking is used as a measure of security, that is, to ensure that the original data is not corrupt or missing in any way.

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Direct Access Method – Hard disk, Zip disk and floppy disk

Formatting a floppy disk or hard disk means preparing the medium to receive data. Mostly when a new disk is bought, the surface are is free and not organized. In order to start writing data onto a disk, one must format it or prepare the area into chunks where the data is stored (like boxes in a room to organise our storage). Formatting prepares the disk into round concentric circles called TRACKS (like an athletics track). Tracks are then subdivided into smaller pieces to form SECTORS. Even though the outer sector is larger in area than the inner sectors, they will still hold the same amount of data.

Floppy disks rotate at about 360rpm. Data transfer is around 10k to 100k per second. They consist of 80 tracks and of 256 sectors per track. Floppy disks are lightweight, portable, relatively cheap,

rewritable, and can store 1.44Mb of data (they can store more if special software is used for compression of data). Magnetic medium is brown in colour and soft. Disk allows random access. This is achieved by storing each new file at the start of a new sector. If for example, program one occupies sectors 0, 1, 2 and half of sector 3, file two will be stored in sector 4, leaving half sector 3 empty. All programs stored on disk are catalogued in a directory for easy searching. This is done by the operating system. A file is not necessarily stored in sequential sectors but may be fragmented.

Hard disks are not readily portable (some exist which can be removed), becoming cheaper, rewritable, typical storages nowadays at around 30GB (and more). Magnetic medium is shining silver metal and

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hard. Since hard disks are getting larger and larger an important factor to look at when buying a new hard disk is its access time.

Zip disks are very popular for making backups both in the industry, offices and at home. They are magnetic disks but the media is made of high density magnetic material – meaning that the surface is more densely packed with magnetic particles. This allows for high density of data too. Zip disks use special compression software which packs large amounts of data into smaller sized data. Zip disks require special zip drives and special software compression. Typical zip disks are of 100Mb and 250Mb capacities and are small cartridge like in shape.

Zip Disk

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A stack is a number of rigid disks put on top of each other on a spindle or pivot. Files are accessed by making reference not just to the track and sector but also on side number. Same track numbers on different disks are known as cylinders. These were used on mainframe computers.

Direct Access Method – Optical Disks

This is the most promising secondary storage technology; optical storage involves the use of a high power laser beam to burn microscopic spots off the aluminium disk’s surface coating. Data is represented by the presence of holes along a smooth shining surface. Binary ‘0’, aluminium surface burnt out presence of holes. Binary ‘1’, aluminium surface reflects back. A much lower power beam is then used to retrieve the data. The patterns of spots detected by the laser during a read operation are converted into electronic signals used by the computer.

The capacity of the optical disk is enormous compared with most magnetic disk storage devices. A 5.25” optical disk, little larger in size than a diskette, can store between 600Mb to 17GB.

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CD-Rom (medium)

CD-Rom stands for Compact Disk Read Only Memory – note that these disks are for reading and only store the information that the manufacturer records on it. The user cannot erase, change, or add to it, only read it. This type of optical disk is used primarily for storing huge amounts of data – such as government statistics, encyclopaedias, medical reference books, and dictionaries. CD-Rom’s have an access time of about 160ms and a transfer rate of up to 800KB/s

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CD-R – WORM (medium)

WORM stand for Write Once Read Many

This type of video disk allows for recording onto the next free tracks until the disk is full. This type of medium is recorded only once.

CD-RW – Erasable Optical Disks (medium)

Erasable optical disks are an alternative to large capacity hard disks. They store 1,400 times as much data as diskettes. In contrast to CD-Rom’s, erasable disks can be modified and erased. The removable disks provide convenience and security along with huge storage capacity. Optical disks can also be used to back up fixed hard disks. Many experts think that optical storage will become the most efficient inexpensive storage method. They offer 15,000 tpi (tracks per inch), compared to 96 tpi of floppy disks.

NOTE that although nowadays we have re-writable CD’s they are still not suitable for storing word processing documents, databases etc. for they do not allow editing and manipulation (Save to CD cannot be performed like to a floppy disk). They can only store an exact copy, which cannot be altered. Be careful to exam questions regarding this.

DVD – Digital Video Disk (medium)

The DVD medium is similar to the CD-Rom disk. There are no visible differences except that the tracks are more closely packed. Therefore there are more tracks on the DVD than on the CD-Rom disk. These new disks allow far more storage than the previous CD-Rom and today are available with a capacity of around 17GB. This large amount of storage enables the inclusion of more video clips; in fact, the most significant development sector for the DVD is in the film industry. One can already rent full feature films on DVD’s. The advantage of DVD’s over the original video cassette tapes is the high quality digital sound and video. These films are sometimes also provided with different language tracks pre-recorded so one can choose the language in which to listen to the sound track

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Optical Disk Drives

A CD-Rom is similar to an audio CD but with the recording tracks much thinner and closer to each other. Therefore, the disk would be holding much more tracks for recording. At first there were two or three major standards, which meant that not all CD-Rom drives were compatible to read all CD Rom’s. However agreement was reached and a standard was set up. The CD-Rom drive uses a laser light to read data on the tracks while the disk is spinning at a standard speed. These speeds have been

increasing rapidly from 1x to 40x. A high-speed CD-Rom drive, allows for better access time and better refresh rates.

Access Time – the time taken for the transfer of data from the CD to the computer

Refresh Rates – higher refresh rates prevent the video picture from flickering.

DVD devices operate much on the same principle as CD-Rom drives. They use a laser light to trace the video signal on the tracks. The tracks are however more compact and since the layout of these tracks is totally different from that of the CD-Rom drive new standards had to be agreed.

Backing Storage Device, Media and Access Type

DEVICE MEDIA TYPE ACCESS

Cassette Tape Drive Cassette Tape Magnetic Serial

Reel to Reel Tape Drive Reel Tape Magnetic Serial

Floppy Disk Drive Floppy Disk Magnetic Direct

Hard Disk Drive Hard Disk Magnetic Direct

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B

O O L E A N

L

O G I C

Computers are effectively complex calculators. All inputs to the computer from keyboard, mouse and other input devices must be translated to numbers. This is done so that the computer would be able to work out the problem and produce the required output.

The computer uses TWO numbers:

1 and 0

Discrete (Digital) and Continuous (Analogue) Data

Discrete data or digital data consists of a set of pulses, which may be counted. A switch can be either on or off (1 or 0). Integer numbers are also discrete – you cannot have a whole number between 5 and 6 for example. Other examples of discrete data are car mileometer readings, heartbeats etc.

Modern computers can only store and process digital data. Hence any analogue data which needs to be processed by a computer must be first converted to digital form. This is done by taking samples of the analogue data at fixed time intervals. These samples are then converted to the digital equivalent. Modems are used to convert analogue data to digital and vice versa.

Examples of Analogue type:- Speedometer, Thermometer, Spring Balance

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Logic Gates

Logic gates are electronic devices that are used in the computer to work out these mathematical calculations. Logic gates are fed with a particular binary number consisting of two or more digits and generate a single output. Logic gates have rules which determine the output of a logic gate depending on the input of the logic gate. These rules are known as truth tables.

In this course we are going to concentrate on three basic logic gates:

- AND Gate - OR Gate - NOT Gate

What is a logic circuit?

A combination of logic gates which perform several logic functions such as: - control the flow of information

- carry out arithmetic and logic (ALU) functions - help to store information and time operations

OR Gate AND Gate NOT Gate

A

B

C A

B

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The OR Gate

The OR gate can be compared to an electric circuit consisting of a battery, a bulb which represents the output, and two switches, switch A and switch B which represent the inputs connected as shown above.

Two inputs (A and B), when combined in an electrical circuit using an OR Logic Gate will yield an output (C) which is equal to either 0 (false) or 1 (true), depending on which values, 0 or 1, the inputs have. In general, OR is true when either or both inputs (A and B) are true, otherwise, OR is false.

The following truth table shows when an OR Logic Gate is true and when it is false.

Input A Input B Output C

1 1 1

1 0 1

0 1 1

0 0 0

The only time Output Y is true (equal to 1) is when either or both Inputs A and B are true (equal to 1);

when both Inputs A and B are false (equal to 0), Output Y is also false (equal to 0).

The AND Gate

The AND gate can be compared to an electric circuit consisting of a battery, a bulb which represents the output, and two switches, switch A and switch B which represent the inputs connected as shown above.

Two inputs (A and B), when combined in an electrical circuit using an AND Logic Gate will yield an output (C) which is equal to either 0 (false) or 1 (true), depending on which values, 0 or 1, the inputs have. In general, AND is true only when both inputs (A and B) are true, otherwise, AND is false. (When any Logic Gate is true, it means that electrical current is able to go through it; when it is false, electrical current is not allowed to go through it.)

The following truth table shows when an AND Logic Gate is true and when it is false.

Input A Input B Output C

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1 0 0

0 1 0

0 0 0

The only time Output Y is true (equal to 1) is when Inputs A and B are both true (equal to 1), otherwise Output Y is false (equal to 0).

The NOT Gate

The NOT Gate has only one input and one output as shown in the table before.

Whenever an Input is true (only one Input is required), the NOT makes it false. Similarly, whenever an Input is false, the NOT makes it true. The NOT gate is also known as an inverter.

The following table shows when Output C is true and when it is false.

Input (A or B or Combination) Output C

1 1

0 0

Output combinations VS Inputs

The amount of inputs to a logic gate will determine the number of possible outputs. This can be worked out by following this simple calculation:

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A gate with 4 inputs 24_{= 16}

Etc….

Boolean Expressions

What is a Boolean expression?

• An expression which uses Boolean operators such as AND, NOT, OR. • An expression that results in a value of either TRUE or FALSE

The logic circuits (diagrams) can be represented by using Boolean algebra.

When building the Boolean expression, the following symbols should be used at all times:

1) A OR B represented as A + B 2) A AND B represented as A.B 3) NOT A represented as Ā

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Example:

In order to work out a Boolean expression, one must follow some basic steps:

a. The Boolean expression is a representation of the logic circuit

b. The expression is the relation of the output with respect to the relative gate inputs c. Always work out the Boolean expression starting from output to the input

d. The logic circuit is made up from a number of gates, thus it is good practise to see the circuit as being made up of a number of gates rather than as a whole

A

B C

X NOT

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- Practical Examples -

Example 1:

The figure below shows a logic circuit:

a. Complete the truth table for:

A B X C

0 0 1 0

0 1 1 1

1 0 0 0

1 1 0 0

b. Represent the logic circuit in Boolean algebra:

C = ((NOT A) AND B)

C = ((Ā) . B)

A B NOT X AND C

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The figure below helps to understand better how the Boolean expression above was constructed:

C = ((Ā) . B)

A B NOT AND C

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B

I N A R Y

C

O N V E R S I O N S

Objectives:

1. Representation of numbers in binary

2. Conversion from Binary to Decimal and vice versa 3. Conversion from Hexadecimal to Decimal and vice versa 4. Conversion from Hexadecimal to Binary and vice versa 5. Perform Binary Arithmetic – addition and subtraction

6. Understand the concept of registers, complementation, ranges, left and right shifts 7. Numerical overflow

8. How to calculate number of bits required representing a number 9. Representation of negative numbers

10. Representation of characters – ASCII and EBCDIC

Number Systems

As discussed in the Boolean Logic chapter, the computer is basically a complex calculator. A computer must translate everything to number form and perform a series of calculations before it can work out something. It does not use the Decimal number system as us humans but uses Binary numbers and Hexadecimal numbers. This chapter will help us to understand better how the conversions are made, and how calculations are achieved.

Why Binary?

A computer, being an electronic machine is made up of switches, that is, the circuits are either in the ON state or in the OFF state. The binary number system is the ideal number system to represent the two-states because it has only two digits: zero and one. A term commonly used to refer to 1 or 0 in binary system is bit.

A bit is defined as a Binary Digit that can be either 0 or 1. A group of 8 bits is called a byte. The number of bits processed by a processor is called the wordlength and is determined by the computer

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manufacturer. The following terms are often used as a unit of memory measure of a computer. For example, we speak of gigabytes of hard-disk space and megabytes of RAM

• A BIT (Binary Digit) is one of the digits used in binary notation, i.e. 0 or 1. • A BYTE is made up of 8 bits.

• A KILOBYTE is 210 bytes = 1024 bytes.

• A MEGABYTE is 210 Kilobytes = 1024 Kilobytes. • A GIGABYTE is 210 Megabytes = 1024 Megabytes.

Decimal or Denary system

As already mentioned, human beings use the Decimal number system to perform calculations. This number system is based on the manipulation of 10 basic numbers

System Base Digits Used

Decimal Base 10 0,1,2,3,4,5,6,7,8,9

Binary System

The computer is made up of electronic circuits, which in turn are made of switches. A switch can be either ON or OFF, meaning it can only have TWO states.

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Hexadecimal System

Hexadecimal numbers are used by the computer for addressing the memory locations. Hexadecimal system uses a 16-digit system

Hexadecimal Base 16 0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F

As the Hexadecimal system has more digits than the Decimal system, letters had to be added to the system: A = 10 B = 11 C = 12 D = 13 E = 14 F = 15

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Decimal to Binary Conversion

In order to convert a Decimal number to Binary, we must divide the decimal number by 2 successively. If the number has a remainder, this is equal to 1, if not it will equal to 0:

Example: 2 4 2 15 2 48 2 2 r0 2 7 r1 2 24 r0 2 1 r0 2 3 r1 2 12 r0 0 r1 2 1 r1 2 6 r0 0 r1 2 3 r0 2 1 r1 0 r1

ANS: 0010 ANS: 01111 ANS: 0110000

Most Significant Bit (MSB) and Least Significant Bit (LSB)

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Binary to Decimal Conversion

1st_Method:

Using a general formula to convert to decimal from any base:

(n x basex_{) + ..(n x base}3_{) + (n x base}2_{) + (n x base}1_{) + (n x base}0₎

Example – For Binary system (Base 2):

Convert 11101 to Decimal (1 x 24_{) + (1 x 2}3_{) + (1 x 2}2_{) + (1 x 2}1_{) + (1 x 2}0₎ (1 x 16) + (1 x 8) + (1 x 4) + (0 x 2) + (1 x1) 16 + 8 + 4 + 0 + 1 =29 2nd Method:

Short method of conversion – by weight

Binary place value 27 26 25 24 23 22 21 20

Weight 128 64 32 16 8 4 2 1

Example – For Binary system (Base 2)

Convert 11101 to Decimal

1 1 1 0 1

16 8 4 2 1

16 + 8 + 4 + 0 + 1 =29

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Convert from Decimal to Hexadecimal

1st_{Method – By Division}

In this method, the decimal number is divided by 16. In this way a remainder from 0 to 15 is obtained. You must keep in mind that in Hexadecimal we have to convert from 0 to 15 into A to F respectively.

Example:

16 30 16 100 16 1024

16 1 r14 16 6 r4 16 64 r0

0 r1 0 r6 16 4 r0

0 r4

ANS: 1 14 ANS: 6 4 ANS: 4 0 0

ANS: 1 E

2nd Method – By Grouping

In this method, one must first change the decimal number to binary. Secondly, the binary number must be grouped in groups of 4 bits each, starting from the least significant bit.

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Example:

Convert from Decimal to HEX

Decimal Number: 166

Step 1: Convert to Binary: 10100110

Step 2: Group in 4 bit groups: 1010 0110

Step 3: Change to decimal: 10 6

ANS: A 6

Convert from Hexadecimal to Decimal

1st_Method:

As used in Binary to Hexadecimal conversion we are going to use the same method. This can be shown more clearly through the following example:

Convert A516 to Decimal

A516 = (A x 161) + (5 x 160)

= (10 x 16) + (5 x 1)

= 160 + 5

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2nd Method:

The second method involves the Hexadecimal number being grouped. Secondly, each number is

converted to a 4-bit binary number. Thirdly, each 4-bit number is grouped in a single binary number and finally this number is converted to decimal.

Convert B316 to Decimal

HEX Number: B3

Step 1: Divide into single numbers: B 3

Step 2: Convert each number to binary: 1011 0011

Step 3: Regroup: 10110011

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Converting from Hexadecimal to Binary

Converting Hexadecimal numbers to Binary is relatively simple. One must first get each HEX number and convert it into a 4-bit binary number. Finally, the individual 4-bit binary numbers are grouped together to form a single binary digit.

Example:

Convert A4F16 to Binary

HEX Number: A4F

Step 1: Divide into single numbers: A 4 F

Step 2: Convert each number to binary: 1010 0100 1111

Step 3: Group together: 1010010011112

Convert from Binary to Hexadecimal

Converting from Binary to Hexadecimal follows the same principle as used in the HEX to Binary conversion. The Binary number is first divided into 4-bit binary groups. Each group is converted to decimal and then finally to HEX.

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Example:

Convert 110011012 to Hexadecimal

Binary Number: 11001101

Step 1: Divide into 4-bit groups: 1100 1101

Step 2: Convert to decimal 12 13

Step 3: Convert to HEX C D

= CD16

Binary Arithmetic

As mentioned before, the computer is a complex calculator and certain arithmetic calculations take place. In this course we are going to concentrate on learning how to perform addition and subtraction on Binary numbers.

Addition:

Since in Binary we only use two numbers; 1 and 0 calculations are very simple to understand. However, some rules have to be followed:

0 + 0 = 0 0 + 1 = 1 1 + 0 = 1 1 + 1 = 0 carry1

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Example:

Add the following binary numbers: 1) 1101 + 1100 2) 1000 + 0111 Sum (1) Sum (2) 1101 + 13 1000 + 8 1100 12 0111 7 11001 25 1111 15 Subtraction:

Subtraction is not as easy as addition, since computers are not capable to perform subtraction. For this reason, we must use addition. Consider the following

Subtract X from Y = Y – X ADD (-X) to Y = Y + (-X)

In the end the two above examples will give the same result. This concept is known as

COMPLIMENTATION. In order to assign a negative quantity to a binary number one must perform 1’s and 2’s compliment.

1’s Compliment

In order to find the one’s compliment of a binary digit one must replace ones (1’s) with zero’s (0’s) and vice versa.

Example:

Find the one’s compliment of 11001010

Binary digit 11001010 Convert 00110101 Carry 1

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2’s Compliment

To achieve the two’s compliment, you must add a binary 1to the one’s compliment of a binary number Thus following the result obtained in the example above we have:

One’s compliment 00110101

ADD 1 + 1

Two’s compliment 110110

Subtraction Rules

1. Arrange binary digits to have both the same length 2. Calculate 2’s compliment of number to be subtracted

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Step 1:

110 – 011 110 + ( - 011 )

Step 2:- Find two’s compliment of the negative number Number 011 1’s compliment 100 Add 1 +1 2’s compliment 101 Step 3: 110 + 101 1011 Ignore the carry so ANS is: 11

Registers

In our computer, information is held in the form of Binary digits and stored in Registers, these being like binary containers or drawers. Registers have certain limits or sizes; in other words an 8-bit register cannot contain a 6-bit binary digit.

A number that it is too big to be represented in a register of a particular size causes a Numerical Overflow Error.

For Example:

A 3bit register is used to store the number 810

810 = 10002 – As it can be clearly seen you need 4 bits to represent the decimal number 8. In this case

an Overflow Error will be generated.

A Number overflow error can also be generated if the number is too small to be represented in the register.

A register can contain integers, that is the quantity of a whole number. This whole number can be positive, negative or zero.

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Unsigned Integers – can only be positive or zero. If we take a 3-Bit digit, we can have the following numbers: Example: Binary Integer 000 0 001 1 010 2 011 3 100 4 101 5 110 6 111 7

In order to determine how many different combinations or codes can be obtained using a number of digits; one can use the expression 2n.

Example: How many different combinations can be obtained using 8 bits?

28 = 256 combinations

To determine the largest number that can be obtained using a number of bits one must use 2n_{- 1}

Example: What is the largest number that can be represented using 8 bits?

28 - 1 256 – 1 = 255

We subtract one since the numbers start from zero. In this case the range is between 0 and 255 Thus, the larger the size of the register, the greater is the largest number that can be stored in it as illustrated in the table below:

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• Sign and Magnitude Representation • One’s Compliment Representation • Two’s Compliment Representation

One’s compliment and Two’s compliment were discussed earlier when we dealt with the binary subtraction.

Sign and Magnitude representation

This mode has a bit after the most significant bit that shows if the number is positive or negative. When this bit is 1, it is negative and when it is 0 it shows that it is positive.

Example: The 4-bit register in the example is representing -6

The Range of Signed Integers

In order to obtain the range of signed integers that can be represented in an X-bit register, the following expression can be used:

- (2

n-1

) < x < + (2

n-1

-1)

0 1 1 0

0 means Positive 1 means Negative

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Example: What is the range of signed integers that can be represented in a 4-bit register?

- (2

4-1

- 1) < x < + (2

4-1

- 1)

- (2

3

- 1) < x < + (2

3

- 1)

- (8 - 1) < x < + (8 - 1)

- (7) < x < + (7)

This shows that the range is between -7 to 7

Representation of characters

As we already know, all information going in the computer must be changed to binary numbers. Thus each character must be assigned by a numerical code referred to as a Character Code.

The Character Set is the group of codes that can be used. The number of codes that can be created in this character set is dependant on the size of the bits used to store the character.

Example: if an 8-bit is used, 256 (28) characters can be represented

There are two standards that are widely used: - ASCII Character Set

- EBCDIC Character Set

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A

P P L I C A T I O N

S

O F T W A R E

1. Hardware and System software (Operating System) alone do not provide a single specialised task

2. Application Software is a type of software that performs task to directly benefit or assist the user

3. Application Software is installed on top of an Operating System such as MS Windows. The Operating System itself is NOT a type of Application Software

4 MS Windows is a popular Operating System on small computers. Windows provides an easy interface between the computer and the user. It uses pictures (graphical representations) which look like ‘push buttons’ on the screen and the user can use the mouse to select them. This interface idea is known as Graphical User Interface (GUI). The following image shows the familiar GUI of MS Windows XP

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Definition of Application Software:

A complete system for a particular application supplied by an external body or written in-house, for general use by individual installations using their own data.

Application Software Examples: 1. Word Processing 2. Spreadsheets 3. Databases 4. Accounting 5. Games 6. Internet Browser 7. Desktop Publishing

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Different Application Software:

APPLICATIONS SOFTWARE Productivity Software Business Specialty Software Entertainment Software Home / Personal Software Education / Reference Software Word processing Spreadsheets Personal finance Presentation Graphics Database managers Communications Groupware Desktop accessories Suites Browsers Desktop publishing Project management CAD / CAM Drawing Painting Hypertext Multimedia authoring (and multimedia software components such as animation software, music/MIDI, sound capture and editing, video capture and editing, speech synthesis, drawing, painting, hardware support ) Games Etc.. Cookbooks Medical guides Home decoration Gardening Home repair Etc.. Encyclopedias Phone books Almanacs Library searches Etc..

Off the shelf and Custom made Application Software

The Application software can either be bought off the shelf or else custom made to the buyers’ needs.

Off the shelf:

Are the ones we find in the computer shops developed by large software houses, made for the general user. Since the market for such software is larger, the price is lower. Custom made:

These are designed to meet the buyers’ needs and specifications, and can be guaranteed to full fill all the functions required by the customer.

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Advantages and Disadvantages of buying off the shelf software Advantages / Benefits (ref to book pg 277):

1. Cheaper in price.

A wider market is reached; more people are ready to buy the software 2. Quicker and less costly implementation.

Can be performed by the user, implementation is simple and doesn’t require knowledge on the software

3. Greater system efficiency.

The software would be fully compatible with the operating system 4. Proven and tested.

Tested thoroughly by a specialized team 5. Documentation provided with the package

Reliable documentation that can help the user to install and operate the software 6. Changes automatically catered for by the supplier

The different options to change settings are provided by the software manufacturer 7. User friendly

Simple, easy to understand and to use Disadvantages / Reluctance:

1. Processing logic does not always fit the true situation of the hardware, requirements are difficult to meet

Examples of requirements that are hard to meet:

Hard disk space – Not large enough, and not enough RAM

2. Too ‘Generic’, might have to change present procedure to accommodate the package (Should be vice versa)

Due to the limitations offered by this type of software, it might be needed to adopt the present procedures to the software. This can be very stressful for the user and thus prone to errors.

3. The package is not efficient in certain aspects (some information irrelevant to the environment).

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Some features of a user friendly software: i. Easy to use:

Lets the user do the job with minimum effort ii. Robust:

Application should be tolerant to user’s mistakes and allow recovery if something should go wrong.

iii. Attractive and ergonomically designed:

Attractive screen layouts and colours; Ergonomically designed: Working in a way the user finds it natural and comfortable.

iv. Helpful:

If a mistake is done, the application should give the user a clear explanation of what was wrong and how to recover from the error. The system should issue warning messages and request confirmation before allowing the user to proceed.

On-line help, through telephone line or through Internet.

One should not underestimate the importance of user-friendliness for the success of a system – all too often a computer system does not succeed simply because users do not accept it.

Integrated packages (ref book pg 279)

Care should be taken that application software would be fully compatible. To eliminate the risk of incompatibility is to purchase an ‘Integrated package’.

An Integrated package is a package of different application software such as Word Processors and Spreadsheets but with reduced functions. Examples of application software packages are ‘Microsoft Works’ and ‘Lotus Works’. This kind of application software costs less and takes less space on the hard disk.

Another solution for incompatibility is to purchase a ‘Suit of applications’ such as ‘Microsoft Office’.

This type of package would be made up of different full applications software. These cost more than the integrated software package, but less if you had to buy the applications one by one. Takes more space on the hard disk, for example MS Office 2003 takes about 400Mb of hard disk space.

Applications of Information Technology Common to most Organizations (ref book pg 279)

Certain computer applications and information systems are universal and equally appropriate for different companies.

Payroll

1. Payroll software mainly deals with salaries, tax and National Insurance of the employees. 2. The two primary outputs of a payroll system are cheques or payslips.

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Accounts

1. The accounting package keeps track of money owed to the company for goods sold or services provided.

2. Production and updates of invoices, bills and statements.

3. The accounts payable systems is the other side of the accounts functions.

4. Monetary transaction that occurs within an organization must be properly recorded (transfer of funds).

5. This kind of application software provides financial statement, which includes the profit and loss statement and the balance sheet.

Inventory Management and Control

1. A fixed-asset inventory record is maintained for each item and includes such data as date purchased, cost, location, and inventory item number.

2. These records are maintained for asset-control and tax purposes.

3. Inventory systems monitor the quantity on hand and the location of each item. Such a system will monitor and help eliminate stock outs (out of stock) and over stocking of raw materials.

Human Resource Development

1. Human resource development systems maintain data on employees, such as educational background and salary history

2. The system includes data on performance reviews, skills, and professional development.

Manufacturing

1. In a manufacturing company, the order entry and processing system accepts and processes customer orders.

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Project Management

1. This application software provides the management with a tool to keep projection within budget and on time.

2. The tasks, which are going to make up the project, are put one after each other in their order so that the project can be finished.

3. This software will give the management a tool to plan the project without involving any expensive measures.

Robotics

1. An industrial robot is best at tasks that are repetitive and tasks that require precision movements, moving heavy loads, and working in hazardous areas.

2. This software application will give access to the robot programmer to load the set of tasks that the robot has to perform to carry out the job.

Computer Integrated Manufacturing

The integration of computers and manufacturing is called Computer Integrated Manufacturing (CIM).

The process usually follows these steps:

1. An engineer uses a Computer-Aided Design (CAD) system to design the part. 2. The design specifications are produced and stored on magnetic disk.

3. The specifications, now in an electronic database, become input to another computer system that generates programs to control the robots and machine tools that handle and make the part.

4. The tools provide data for order processing, inventory management, shop floor scheduling, and general accounting.

Some computer – integrated manufacturing systems go one step further and provide a link between the manufacturer and the customer via electronic data interchange.

Word processors (ref book pg 282)

A WORD PROCESSOR is a program, which is used for preparing documents, typing letters, and producing reports.

Advantages of word processors over traditional typewriters: Ease of correction

Automatic Formatting

Multiple copies and Form Letters Automatic Features

Search and replace facilities Spelling checkers and thesaurus

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Font changes Mail Merge

Other features: Multi column text, grammar checker, table formatting, inclusion of drawings

Desk top publishing (ref book pg 284)

Desk Top Publishing (DTP), involves using a computer, mouse, scanner, printer and Desk Top Publishing application software for mixing text and graphics to produce high quality printed output for commercial printing. The emphasis is not on the entry of text (as it is with word- processing), but the ability to compose text and format the document in a manner that comes close to the quality achieved with professional typesetting equipment.

Desktop Publishing Software is used for: Catalogues

Brochures Presentations Reports

Desktop Publishing Software is NOT used for: Memos

News releases Addressing Mailing list