All Topics

A Computer System

Algorithms and Flowcharts

Applications Software

Bar Codes

Batch Processing

Billing Systems

Bits and Bytes

Booking Systems

Bulletin Boards

Bus, Star and Ring Networks

Cache

CAD/CAM

CAL and Computers in School Administration

CAM

Codes of Practice

COM

Computer Control in Hospitals

Computer Misuse Act

Control Systems

CPU (Central Processing Unit)

Data

Data Collection

Data Compression

Data Encoding

Data Protection Act

Data Security

Data Transfer

Data Transmission

Data Validation

Data Verification

Databases

Digital Camera

Distributed Systems

Documentation

E-commerce

Electronic Office and Safety

Email

Embedded Systems

Employment

Evaluation

Expert Systems

Expert Systems in Medicine

Fax

File Access

File Backup

File Generations

File Merge

File Operations

File Structure

File Update

Fixed Length Fields

Floppy Disks

Graph Plotter

Graphics

Graphics Tablet (Pad)

Hard disks

Hardware and Software

Human Computer Interface

ICT in Education

ICT in the Home

Inkjet Printers

Interactive

Interactive Digital TV

Internet

Internet as a Source of Information

Intranet

Joystick

Keyboards

Laser Printers

Libraries

Light Pen

Magnetic Stripe

Magnetic Tape

Mail Merge

Mainframe

Memory

MICR

Microcomputer

Mobile Phones

Modelling Systems

Modem

Money

Monitors

Mouse

Multi-access

Multiprogramming / Multitasking

Network Hardware

OCR

OMR

Operating System

Optical Disks

Output

Parallel Processing

Payroll

Portable Data Entry

Process Control in Industry

Real Time (Process)

Real Time (Transaction)

Removable Media

Robotic and Embedded Control

Scanner

Sensors and Data-logging

Software Piracy

Sound / Speech

Sound Output

Spreadsheets

Stock Control and Order Processing

Supermarket

System Flowchart

System Security

Systems Analysis

Systems Software

Teleconferencing (Videoconferencing)

Teleworking

Testing

The Need for Backing Store

Touch Pad

Touch Screen

Tracker Ball

Types of Files

Types of Network

Variable Length Fields

Video Camera

Virtual Reality

Viruses

Weather Forecasting

Web Browser

Why Use ICT?

Word Processing

A Computer System.

A computer system has three main stages :

1. The Input Stage - where data is put into the computer. 2. The Processing Stage - where the data is processed. 3. The Output Stage - where the results are displayed.

A computer also needs to store data for later use.This is done on a backing storage device.

 

A typical computer system :

 

The arrows show the flow of data.

Algorithms and Flowcharts

An algorithm is a sequence of steps used to complete a task.

Algorithms may be presented...

in words as a flowchart in structured code  

A computer program is an algorithm written for a computer in a special programming language.

 

The word 'sequence' implies there is an order to the steps.

Example in words : Go straight on to the traffic lights, turn left and take the third turning on the right. If the red gate is open then go through it, otherwise go through the green gate.

Example as a flowchart :  

Flowcharts have terminators (Start and Stop boxes)...and the algorithm is determined by

direction on the flow lines. 

Decision boxes are diamond shaped.

Example in structured code :

 

Go straight on to the traffic lights;Turn left;Take the third turning on the right;If the red gate is open then      go through the red gateelse      go through the green gateend if;

Each line is executed in turn...

Applications Software

An applications program enables a user to perform a specific function.

An applications package is a complete set of applications programs and documentation.

Examples : 

school management software;  theatre booking system; taxi service system; air traffic control system; computer game

If an application program can be used in many different areas it is usually called a generic program (or content-free program).

Examples: 

a word processing program (can be used to produce a legal document, a newspaper article, a school homework essay etc)

spreadsheet program a database program.

 

Applications programmers write the software using a computer programming language. Programs can be configured to the specific needs of a user by altering

the coding.

 

Bar Codes

A bar code is a set of parallel printed lines of differing thicknesses which are used to store coded information about an item.

Bar codes are read using a Bar Code Reader, which can be in the form of a hand-held ‘wand’ or a stationary laser scanner over which the bar code is passed.

This method of data entry is used in big shops and supermarkets and in libraries.

 

Advantages

a fast method of data entry eliminates possible human error

Disadvantages

scratched or crumpled barcodes may cause problems

Batch Processing

A batch processing system is one where programs and data are collected together in a batch before processing starts.

Each piece of work for a batch processing system is called a job. A job usually consists of a program and the data to be run.

Jobs are stored in job queues until the computer is ready to process them.

There is no interaction between the user and the computer while the program is being run. Computers which do batch processing often operate at night.

Example : Payroll - when a company calculates the wages for its workforce and prints payslips.

 

Billing Systems

An example of a billing system is - electricity payments. Every customer receives an electricity bill which must be paid.

The electricity company has a large database (master file) of all its customers. The file will also include information such as latest meter readings, how much electricity the customer has used this year, how much has been paid etc...

At regular intervals, meter readers go round each house to read the electricity meter. The reading is recorded onto pre-printed forms.

 

The forms are all collected and input to the computer system. This may be done using OMR or OCR, or by manually keying in the data.

The data must be validated before it is processed to make sure no 'silly' data is input.

Keyed data will need to be verified to check for transcribing errors.

 

A document produced by the computer which is later used as input is called a turnaround document.

The electricity bill for each customer is calculated by the computer and printed. These bills will be posted to the customers.

 

The customer then pays the bill by either sending a cheque or by credit/debit card. Some customers may pay by monthly standing orders or direct debits.

Payments received will need to be recorded as transactions on a transaction file and used to update the master file.

 

For some billing systems statistical analysis can be done on ...

customer usage or spending patterns (eg seasonal variations)

payments

 

Bits and Bytes

The size of a computer's memory is measured by the amount of data which can be stored in it. This is measured in bytes.

 

Data is stored in memory as a number of 0s and 1s. Each of these is called a bit (Binary digIT), so for example the number 0110 is a 4-bit binary number.

8 bits is called 1 byte.

 

 

The reason that binary numbers are used is that memory consists of millions of two-state devices (think of them as

switches). 

Each of these can only be in one state (0) or the other (1).

Using the ASCII system of coding each character is stored as a unique 8-bit pattern. (A is 01000001; B is 01000010 etc..).... 

1 byte of storage is needed to store one character, so to store the word ‘FRED’ would need 4 bytes of storage.

 

ASCII stands for American Standard Code for Information Interchange...Most computers use the same system so data can be transferred from one

computer to another.

A Kilobyte is 1024 bytes. A Kilobyte is usually abbreviated to K, and you will sometimes see a computer described as having 640K RAM. This means that there are 640 kilobytes of memory in the computer.

A Megabyte (abbreviated to Mb) is 1024 kilobytes,

so 1 Mb = 1024 x 1024 bytes = 1048576 bytes (approx 1 million)

A Gigabyte (abbreviated to Gb) is 1024 Mb

so 1 Gb = 1024 x 1048576 = 1073741824 bytes (approx 1 billion)

 

You can think of data stored in memory or on disc as looking

like..

101100101100101001101001000101111110101110110100110110100010001000010010100100101001011011101010...

Booking Systems

It is now possible to make bookings on-line for holidays, trains, planes, hotel rooms, theatre performances...and many others.

A travel agent for example, may have computers in all its branches directly connected to a central computer where a database of all bookings is stored. This is an example of a multi-access system.

 

When a booking is made, the customer will need to provide input details  (name, date, place, number of people etc). 

These details may be entered ...

at a computer terminal in a multi-access system. on a form on an Internet web page. by transcribing them from a paper booking form. by typing them in when in telephone

communication with the customer.

 

This form (on an Internet web page) is used for collecting details of a passenger's booking on the Eurotunnel. These details are then used as input data when the booking is made.

This data is validated to check if the details are sensible. The computer will check to see if the booking is available, and, if it is, the booking is made and it will then store the booking details in the database.

Documents will need to be output to give to the customer, confirming the booking and giving details about it.

 

As soon as a customer makes a booking it has to be processed immediately, so that no other customer can make the same booking. This means it is a real-time (transaction processing) system.

It is essential that no data is lost, so the database will have to be regularly backed up - possibly using a tape streamer.

If payments for the booking are required, then these can

generally be done on-line using a Credit card or a Debit card. If details of these are transmitted over the Internet, the website must be secure so that this information cannot be stolen.

 

Bulletin Boards

A bulletin board is accessible using the Internet and is a place where people who share a common interest may leave or read messages.

 

Especially popular on Usenet, enabling worldwide 'newsgroups' to exchange information on topics of interest.

Bus, Star and Ring Networks

Network topologies (ways in which computers are arranged in a network)

Bus

Each computer is linked to a bus (cable) and there are terminators at each end of the bus. Less cabling but can be

slow if there are a large number of users.

Star

Star Network

All computers are connected to a central computer (file server). The disadvantage is that if this file server breaks

down then all the computers are affected.

Ring

Token Ring Network

'Tokens' of data are passed round the ring (in one direction only) and collected by the receiving computer. A faster

system and it is easier to add more computers.

 

Cache

Modern software usually requires a large amount of memory in a computer in order to operate.

 

Most computers use a part of the hard disk as extra memory. Data stored in memory which is not actually needed immediately is temporarily moved into the disk cache and moved back into memory when it is needed.

The computer will seem to have more memory than it really has.

Access from disk is much slower than from RAM so the speed of operation will be reduced if disk cache is used.

CAD/CAM

CAD stands for Computer Aided Design.

CAD is used for displaying and editing designs on the computer. Calculations can often be made.

Graphics tablets.(Graphics pads)

Input may be from a keyboard, graphics pad or touch-screen monitors.

Some CAD packages allow 3D design...The image can be rotated or viewed from different angles.

Example :

CAD can be used for interior design work. Arranging furniture in a room. This can be viewed from a number of different angles.

The arrangement can be changed on the computer and 'tested' without needing to move actual furniture around.

CAD can be used to design...

cars bridges buildings boats engines circuit boards ...and many

more

Facilities include...

creating and editing new designs viewing designs from different angles adding standard pre-designed shapes from a library calculations (areas, volumes, stresses etc) designs can be tested (eg electrical circuits)

Finished designs may be 

...printed out using a graph plotter. ...used as input for a CAM process....

 

 

CAM stands for Computer Aided Manufacture.

CAM uses a computer to control a manufacturing process. CNC (Computer Numerical Control) machines such as

lathes milling machines drilling machines welding machines soldering machines robots.

...are used to produce the product.

In the CAD/CAM process slight changes to design are quickly and easily made and implemented. The result of any change can be quickly analysed.

 

CNC devices receive the production instructions from the computer as

numbers.

 

A milling machine.

Cutters on a swivelling head receive instructions and shape a block of metal.

CAL and Computers in School Administration

CAL stands for Computer Assisted Learning.

CAL courses may use ...

text - notes and other resources graphics sound - a commentary or music background animation  self assessments - for the student to know how much has

been learned.

You are using CAL right now!

CAL systems use interactive computing.

 

Benefits of CAL...

more interesting learning with interactive systems and multimedia - so greater motivation

students can learn at any time students can learn from any place eg home students proceed at their own pace not so many teachers needed

 Pupils generally learn better when they study on their own and can learn at their own pace.

 

Computers in School Administration

Most schools now have a large database of pupil details. This database will store personal data about the pupils as well as the classes they take, their teachers, medical information etc.

This database can be searched to produce eg class lists

Pupil assessments may also be recorded (test and exam results) so that pupil progress can be monitored.

Spreadsheets may be used to calculate and monitor the school's financial budget.

Word processing or DTP software may be used to produce documents for the teachers or pupils.

Timetables are produced using special software.

 

A school which has networked computers may have an Intranet which provides web-based resources available at any workstation.

 

Some school may have on-line registration systems where pupils use swipe-cards (with magnetic strips).

 

CAM

CAM stands for Computer Aided Manufacture. 

Output from a computer is used to control CNC manufacturing machines such as millers or lathes...or even knitting machines. (CNC stands for Computer Numerical Control and means that instructions for the machines are given as numbers.)

CAD/CAM is the whole process of design and manufacture using computers. CAD is used to produce the design of a product and the code to run the CNC machine is output. The machine then manufactures the product.

 

Codes of Practice

A Code of Practice is a set of standards that a business would expect its employees to conform to.

It is not legally binding but the business would ask an employee to agree to it before being employed and would be grounds for dismissal if they were not obeyed.

It is always in the best interest of a business to treat its customers fairly and with due consideration - or they will go elsewhere.

It ensures consistency of practice. All employees would conduct their business in a similar way.

 

COM

COM is a technique of reducing documents in size and photographically printing them so that they can be read using a special magnifying machine.

Microfilm is a roll of film and microfiche is a rectangular sheet of film on which many frames (pages of information) can be stored.

 

Microfiche readers are needed to read the very small text and pictures.

Example : Newspapers might be archived on microfiche.

Advantages :

uses much less storage space film lasts longer than paper

Computer Control in Hospitals

The main use of computer control in hospitals is in life-support systems.

Sensors attached to a patient monitor 

pulse temperature blood pressure breathing rate

The readings are taken at regular intervals and used as input to a computer.

If any of these readings goes outside acceptable levels an output signal sets off an alarm to alert the nursing staff.

 

These systems may be used for

patients in intensive care (eg after operations) prematurely born babies

The advantages of this system...

monitoring can be continuously done 24 hours a day no chance of human errors due to eg tiredness frees the nursing staff to carry out other duties

but...disadvantages...

these systems are expensive

Computer Misuse Act

The Copyright Act makes it illegal to copy and use a file or software without the owner's permission.

 

The Computer Misuse Act makes it illegal to...

gain unauthorised access to a computer's software or data (hacking) - including the illegal copying of programs.

gain unauthorised access to a computer's data for blackmail purposes.

gain unauthorised access to a computer's data with the intention of altering or deleting it. This includes planting viruses.

copying programs illegally (software piracy)

A conviction may lead to a fine and a 5-year prison sentence.

 

Exercise : Computer Misuse Act

The Computer Misuse Act was introduced to prevent

Control Systems

The output from a computer may be in the form of a signal to a hardware device.

In a control system, sensors are used to measure a physical quantity and send input to the controlling computer. 

The computer responds by sending an output signal to a control interface which activates various devices eg a switch or an alarm.

The output signal may be sent a to an actuator which activates a mechanical device such as a motor.

 

Commonly used sensors are - heat sensors, light sensors, sound sensors, humidity

sensors, movement sensors.

The control interface is needed because of the different operating characteristics of the computer and the devices.

VirusesCopyright infringementsHackingUsing computer data for blackmail or fraudIllegal deleting or altering of computer data

Example:

A computer may be used to control a greenhouse. Sensors continually send information about the temperature and humidity in the greenhouse to the computer. 

The computer will then analyse the data and send output signals, if necessary, to activate the ventilators or sprinkler systems.

 

CPU (Central Processing Unit)

The Central Processing Unit (CPU) of a computer is the main processor which operates the computer - ie it carries out the instructions of the program being run.

The CPU has three main parts...

The A.L.U. (Arithmetic and Logic Unit) which performs all the calculations.

The Control Unit - which controls the flow of data round the computer by sending out control signals.

Memory - which is used to store data.

A microprocessor

Microcomputers would have a single CPU but parallel computers have a number of processors which share the processing tasks.

 

Data

Computers process data.

Data consists of raw facts and figures.Examples : Exam marks, facts from a survey, readings from a light sensor.

Data can be of different types -

Data Type Examples

Text (alphanumeric) John Smith

Decimal (real numbers)

432.5

Integers 432

Currency £12.50

Dates 12/03/02

Calculated an average of exam marks.

Pictures

Sounds Boo!

Moving graphics / Video Clips

In a computer system, ALL data is represented as numbers.

A computer processes data to output information.

People apply rules and make deductions from this information to produce knowledge.

If we put the wrong data into a computer we will get the wrong results. 

 

(GIGO = Garbage In - Garbage Out)

Data Collection

Before data is input to a computer it needs to be collected.

There are several methods of doing this:

 

Data Capture Forms.

Answers to questions are filled in by people on specially-prepared forms. These forms are called data capture forms (questionnaires) and need to be carefully designed.

These answers will then need to be typed into a computer for analysing. This is called transcribing the data.

Example : A membership form for a club may need to be filled in by a pupil wanting to join.

 

Data preparation is the process of transferring the data into a form which can be processed by a computer.

Some forms can be read automatically by special machines (OMR, OCR, MICR)....

Example : School registers.

...but often the data is typed in...

Data capture Forms must be designed so they have instructions, are easy to fill in and there should be no doubts as to how to enter data. Eg Format of dates should be specified - dd/mm/yy

 

This method is liable to errors when the data is entered into the computer (Transcription errors).

One method of avoiding transcription errors is verification. The data is entered twice by two different people and the computer will only accept the data if the two versions are identical.

 

When data is typed the input screen should be designed to be attractive, easily read and should match the document being copied.

Data Compression

When storing a file, a program can be run which compresses the data so that the data takes up less storage space. 

This is useful when files are to be transmitted over a network or attached to an email as the transfer will take less time.

A disadvantage is that the file will need to be decompressed before it can be used. 

A special program is needed for compression and for decompression although some compressed files will automatically decompress themselves.

 

Some examples of Compression programs are WinZip, PKZip and WinRar

Common file extensions of compressed files are .zip, .rar

Compressed files are often referred to as Zipped files.

Example : Normally each character is stored as an 8-bit binary number. One method of compressing data is to assign the common characters a smaller number of bits and the less commonly used characters a larger number of bits.

Graphics files take up a lot of space and usually include a number of repeated bytes....

eg The data

28 28 28 45 45 45 45 45 81 81

could be stored as

3 28 5 45 2 81

with no loss of information, ....but consists of 6 numbers instead of 10.

 

Data Encoding

Data may be encoded when it is stored. A number of different codes are defined for the data.

For example a gender field may be stored as codes (eg

'M' for Male, 'F' for Female).

This...

makes data entry easier (less to type) saves storage space makes validation easier

 

 

Validation rules can be set to check if gender data entered into a database is either 'M' or 'F'.

Data may also be encoded for security reasons. (encryption)

Data Protection Act

There are many organisations which hold personal information about individuals.

Examples :

Tax Office Doctor / Dentist National Insurance DVLC Police

..and many others.

The Data Protection Act (1998) states that organisations which store personal information must register and state the purpose for which they need the information.

The organisation must...

gather the data fairly and lawfully gather only data needed for the stated purpose make sure the data is not used for any reason other than the

stated purpose make sure the data is accurate and up-to-date make sure the data is secure not keep the data for longer than is necessary

The individual has the right to

view the data stored about him have the data changed if it is incorrect

The exemptions to the Data Protection Act are organisations that hold data about...

National Security Crime

Taxation

The full details of the Data Protection Act can be found at

http://www.hmso.gov.uk/acts/acts1998/19980029.htm

 

Exercise : Data Protection Act

The Data Protection Act states that organisations that hold personal data must register and state the purpose for which the data is needed.

The organisation must make sure that...

(select only the relevant lines)

The individual has the right to...

Exemptions to the Act are organisations which hold data involved with crime, taxes or National security.

Data Security

the data is formatted correctlythe data is kept up-to-date and accuratethe data is only used for the stated purposethe data is passed on to other companiesthe data is kept securethe data is collected fairly and law fullyonly data needed for the stated purpose is gatheredthe data is backed up regularlythe data must not be kept longer than necessary

view data held about themhave incorrect data changedrefuse to have their data stored

Ways of keeping data secure include the following software and physical methods:

Passwords(software)

Password protection usually involves a person typing in...

A User Name - to identify the person.

A Password - to authenticate the person. He should be the only one to know what it is.

If the password is accepted, the person is then authorised to view, or edit the data. Different people may have different levels of authorisation.

 

Encryption(software)

The data may be encrypted (coded) into a form which can only then be decoded by the intended user. If the data falls into the wrong hands it will be meaningless.

 

Voice prints(physical)

A person speaks into a microphone and the computer analyses the voice. If it belongs to an authorised person, the computer allows entry to a room or allows access to a computer.

Locks(physical)

Rooms may be locked. Some computers may have locks on them.

Identity Cards(physical)

In order to gain access to a room or a computer, a person may have to swipe an identity card through a card reader.

 

 

 

 

 

 

Methods of identifying people from biological data are called 'Biometrics' and include fingerprint scans, retina (eye) scans, face recognition.

Backups To guard against the loss of data, backups should be regularly made. These backups should be stored in a separate place, preferably in a fire-proof environment. (Fire-proof safes are available).

File dumps on paper can be a useful back-up.

Transaction Log

A transaction log is a record of all transactions made by a business since the last backup was made. 

If data is lost then it can be re-created by loading the previous backup and re-entering all the transactions.

Data Transfer

Data created using one software package may often be transferred into another. 

The transfer may be between different software packages or between different computers. 

Example : A graphic created using a graphics package may be saved, emailed to another user who could import it into a  word-processed document.

This transfer is possible because of standard file formats. Different applications software will store data in the same format.

 

Standard file formats for graphics

include ....bmp, .gif, .jpeg, .tif etc...

Standard file formats for text include ...rtf, .doc, .txt

Data may also be transferred between applications

using copy and paste.

 

Data Transmission

Data in a network can be transmitted using :

Cable Each computer has a network card installed with appropriate network software, and is linked to another computer using a network cable.

Cable can be twisted-pair, coaxial, or optical fibre.

 

Wireless(Microwave,Infra-red,Radio)

Data is transmitted using radio, infra-red or microwaves.

A wireless hub receives and transmits data to each computer. Each computer needs a special wireless network card.

No cabling involved.

 

Satellite There are now hundreds of satellites orbiting the Earth which can be used to 'bounce' signals off.

Data Transmission speeds may vary. 

If the speed is slow...

a user will find it takes a long time for a response from a computer to be made

it will take a long time to download data

Data Validation

Data validation checks that the data is sensible before it is processed.

Methods used for validation are...

range check This checks that the data lies within a specified range of values.

Eg the month of a person's DOB should lie between 1 and 12

presence check This checks that important data is actually there and has not been missed out.

Eg Customers may be required to have their telephone numbers.

type check A check that data is of the right type.

 Eg number, text etc

length check Checks that fields have the correct number of characters.

Eg A bank account number may always be 10 digits long.

check digits Used for numerical data. An extra digit is added to a number which is calculated from the other digits. The computer checks this calculation when data is entered.

Eg The ISBN number on a book. The last digit is a check digit.

batch totals This checks for missing records. Numerical fields may be added together for all records in a batch. The batch total is entered and the computer checks that the total is correct.

Eg Add the 'Total Cost' field of a number

Presence checks can be carried out by

running queries that look for 'Null' fields.

 

 

 

 

 

 

 

of transactions together.

hash totals This is just a batch total done on a meaningless field.

Eg Add the Telephone Numbers together for a number of Customers.

Data Verification

It is important to prevent errors occurring in data. Verification is used to prevent errors occurring when data is copied from one medium to another. (eg paper to disk, disk to disk, memory to disk)

Methods used for verification...

Double keying

Used to check for transcription errors. The data is entered twice (by two different people). The computer will only accept the data for processing if the two versions are identical.

Visual check Checking for errors by looking through the data. Eg Proof-reading a typed document.

Parity Used to check for transmission errors over networks or between memory and disk.

An extra bit is added to each binary number before it is transmitted. Even parity systems make sure that each number has an even number of '1' bits.

After transmission, each binary number is checked to see if it still has an even number of '1' bits.

Example (Even parity)

If 11010111 is transmitted ...(6 '1' bits)and 11010011 is received ... (5 '1' bits)then the computer knows a corruption of the data has occurred.

 

Databases

A database stores and organises data and allows the user to access it in a number of different ways.

Data is stored in files (tables).

Each file (table) has a number of related records.

Each record consists of related fields.

Microsoft Access is an example of a Database package.

Databases allow the user to..

define the data structure (field names and types) enter and edit data import data from saved files or other applications search for data by using queries (including AND, OR and NOT) sort data into alphabetic or numeric order validate data on entry output reports which may include totals, averages etc... set security levels

 

Digital camera

A photograph can be taken by a digital camera and then downloaded into the computer from the camera.

The resolution of the pictures can be set -  more pictures can be taken at a lower resolution.

There is no need to buy film.

Some digital cameras are used as surveillance cameras 

eg for taking pictures of speeding cars.

 

Distributed Systems

In a distributed system, computers and peripherals are linked together. Each user is not aware of which computer or peripheral he is using.

A user on one computer may be running a program stored on another computer accessing data stored on yet another computer. 

The operating system will control access to the resources.

 

Documentation

All software packages include documentation. 

The User Manual is written for the user and may include...

instructions for installation instructions for use trouble-shooting guide (what to do if it goes

wrong!)

The User Manual is written to make sure the user can use the software and should be written in simple language.

The Technical Manual is written for other programmers or computer experts and may include....

data flow diagrams (or flowcharts) showing how the program works.

program listings

 

The Technical manual is written for other programmers who may need to alter some of the software and may include technical computer terms.

Documentation should explain software (or a system) as simply as possible. This will be helped if long wordy explanations are replaced by...

graphs tables flowcharts diagrams photos

E-Commerce

Shopping over the Internet is increasingly popular.

Retailers create websites which display the items they are selling.

Customers load the web-site and add the items they wish to buy to a 'shopping-basket', and then pay by credit or debit card. (Credit card details are encrypted on secure sites)

The goods are delivered to the buyer's house.

 

Advantages of e-commerce:

greater range of goods can be done from home goods are delivered to the door-step the business does not have to provide and pay for

premises

Disadvantages :

there is a couple of days delay before receiving goods. possibility of credit card information getting into the

wrong hands you cannot see or touch the goods before buying

Electronic Office and Safety

Most businesses use ICT in their office. The aim is to make a paperless office - where all information is sent and received electronically.

In the paperless office...

finding information should be fast costs should be reduced (eg cost of paper) storage space should be minimal

 

Computers would be used...

for word processing eg for documents, letters, contracts... for spreadsheets eg accounts and budgets... for databases eg of customer details, daily transactions... for DTP (Desk Top Publishing) for creating pamphlets,

brochures... for presentations eg annual report...

These computers would be networked.

Email would be used to send messages to customers and between

employees.

An Intranet would store important information used by the business.

The business may use the Internet for advertising and allowing e-commerce.

 

Health risks...

eye strain (looking at computer monitors for too long) neck/back strain - from poor seating arrangements RSI (Repetitive Strain Injury) - tendon injury from using

keyboards too much. fitness problems - from lack of exercise.

The study of the working environment is called

ergonomics.

This picture shows how you should be sitting at a computer!

Other measures for prevention of accidents....

do not bring food or drink near computer equipment. do not overload electric sockets. do not leave wires where they can be tripped over. make sure fire extinguishers are installed.

Email

Email stands for Electronic Mail.

A user can send messages to another computer user.

Each user has a unique email address.

Files (text,pictures, music, video clips etc) can be sent with the message as an attachment.

 

Advantages of email over conventional mail (snail-mail) :

messages arrive much faster (within a few seconds) it is cheaper to send an email one message can be sent to a number of users. attachment files can be sent no stamp needed can be sent from home

 

Disadvantages of email :

you can only send a message to other users with email accounts

email attachments can contain viruses you cannot send physical objects messages can only be sent to other email users unwanted junk email may be sent to you in large amounts! -

filters can be used to eliminate this.

Email facilities may also include..

reply to a received message forward a message on to another user keep an address book of email addresses keep mailing lists so that the same message can be sent to

groups of users

WARNING!- Some viruses spread by sending emails to all the users in the address book.

Embedded systems

An embedded system has processors built in to a machine. These deal with the input, processing and output of data.

 

Examples :

 

Microwave

Washing machine

A guided missile.

Other examples : Traffic lights, digital cameras, mobile phones, calculators, ATMs (cash machines), DVD players, games consoles....and many more...

 

Employment

ICT has changed the nature of jobs. Some jobs have been created and others have been lost...

New jobs created include ...

computer programmers systems analysts computer technicians robot maintenance

Jobs which have been lost include...

boring or repetitive jobs replaced by robots (Eg assembly line)

dangerous jobs replaced by robots office jobs - fewer workers needed

Most jobs now require some ICT skills.

 

Workers have often had to be re-trained to use ICT in their workplace.

 

Exercise : Employment

ICT has caused some workers in repetitive, boring or paper-based employment to lose their jobs

eg

but has created others

eg .

Evaluation

When a new computer system is designed, the question will be asked....What hardware and software will be needed?

The hardware chosen must be appropriate....

it must not be too expensive it must be able to do the job it must be reliable it must not be too difficult for people to use

 

The software chosen must be appropriate....

it must not be too expensive it must do the job without errors occurring it must not be too complex for the users it must be compatible with the hardware is it adaptable if changes happen?

A set of evaluation criteria may be specified. These will be used to measure how well the hardware and software perform.

The measure of 'success' of a system will be by how well it achieves the criteria.

manual assembly w orkerrefuse collectoroffice f iling clerktype-setters in a printing f irmtaxi driver

systems analystcomputer programmerrobot maintenance engineernetw ork managerrefuse collector

 

Expert Systems

An expert system is a knowledge-based system which attempts to replace a human 'expert' in a particular field.

The system will consist of

a large database of knowledge facilities for searching the knowledge database a set of rules for making deductions from the data

(inference engine)

Example

A medical diagnosis  expert system (eg MYCIN) would have information about diseases and their symptoms, the drugs used in treatments etc.

A patient is asked by a doctor about symptoms and the replies are input to the expert system. The computer searches its database, uses its rules and makes suggestions about the disease and its treatments. Sometimes probabilities are assigned to diagnoses.

The computer does not take the place of the doctor but can be used to help the doctor make decisions.

Advantages.

The computer can store far more information than a human.

The computer does not 'forget' or make mistakes. Data can be kept up-to-date. The expert system is always available 24 hours a day and

will never 'retire'. The system can be used at a distance over a network.

Disadvantages

Well we don't want to do the experts out of jobs! Lacks the 'human touch'!

 

Expert Systems in Medicine.

 An expert system...

...has a large database of knowledge. ...allows the database to be interrogated. ...has a set of rules (inference engine) for making

deductions.

An expert system is a computer system which simulates the knowledge and expertise of a human expert.

For example, in Medicine, expert systems are being used for disease diagnosis.

The patient's details and symptoms are input, and the system outputs probable diagnoses, recommended treatments or drugs which may be prescribed.

 

Expert systems are not really replacing doctors but are being used to help them. There are ethical and legal reasons for this - if a computerised diagnosis is wrong, who do you sue?

Some patients would feel happier typing medical information into a computer than discussing it with a human doctor...but others would prefer the 'human' touch.

 

The advantages of an expert system over a doctor are...

...a large database of knowledge can be added to and kept up-to-date - it can store more knowledge than a person.

...the system cannot 'forget' or get facts wrong. ...it survives forever. There is no loss of knowledge as

there is when a doctor retires. ...the computer can access specialist knowledge that a

doctor may not have.

 

An expert system would be programmed using an AI (Artificial Intelligence) language such as PROLOG.

Fax

A fax machine copies a document, transmits it down the telephone lines to another fax machine where it is printed out.

The quality of the printout is not good. Fine for documents but not good enough for graphics. Printouts are in black and white.

Fax is short for facsimile.

A fax machine.

File Access

When records in a file need to be accessed there are two ways of doing it....

 

Serial Access

This means ...start at the beginning of the file and access each record in turn until the one needed is found.

 

If files are stored on magnetic tape then serial access is the only method of access.

Direct Access

The computer can calculate (from the key field) where the record is stored in the file, and can then access the record directly from that position.

Direct access of records will generally be much faster than serial access.

 

Direct access can only be used if files are

stored on media such as disk, CD, DVD...

Direct access is also known as random access

File Backup

Backing up a file is saving a copy of the file on backing storage (eg disc or tape).

It is necessary to do this in case the file becomes corrupted or lost. If a file becomes unusable, the backup copy of the file may then be used. Any changes to the file since the last time the file was backed up will need to be done again.

 

Backups of a company's files can take a long time to do and so are often done at off-peak times eg at night

Important files or files that are changed often may need to be frequently backed up. 

 

Sometimes a number of backups are made and stored in different places...eg different discs stored in different rooms or buildings.

If backups are made of large files then they may be compressed before being saved. 

 

A typical scenario....

All the files used by a business are saved onto tape every night using a tape streamer. A different tape is used each night of the week ... but are then re-used the following week.

 

File Generations

When a transaction file is used to update a master file, the process creates a new master file.

The old master file can then be deleted...no, wait!!...there may be problems just around the corner. In practice the old master file would be archived in case the update process has to be re-run.

 

Sometimes the old master file is referred to as the father file and the new master file as the son file.

When the update is next run...

the son file becomes the father filethe father file becomes the grandfather file..etc...

In practice companies will keep several generations of files. This is because there may be a problem (eg disk crash) and the update runs may have to be done again to re-create the current master file.

 

File Merge

To merge two files is to combine them into a single file.

Two files can only be merged together if they have the same structure - the fields are defined the same in each file.

The new merged file contains all the records of both the merged files.

The two files must be sorted in the same way. The

resulting merged file will also be sorted in the same way.

 

Merging files (in words) :

1. A new file is created 2. A record is read from each of the two files. 3. The record which comes first (in sorting order) is

placed on the new file and is replaced by reading a new record from the original file.

4. The process [3] is repeated until both files are empty.

File 1 and File 2 are merged together to create a new merged file which contains all

records from File 1 and File 2.

File 1, File 2 and the new file will ...

have the same data structure be sorted in the same way

Files may be saved on media other than

magnetic tape.

Example :

File 1 :

ID No Sold today305 3309 1316 2317 1

File 2:

The two files to be merged are sorted in order of ID.

ID No Sold today301 5310 1319 7

 

Merged file :

ID No Sold today301 5305 3309 1310 1316 2317 1319 7

 

The merged file is also sorted in order of ID.

Any number of files may be merged together if they are properly sorted and have the same data structure.

 

File Operations

The common operations carried out on files are :

 

Sorting

 

Files may be sorted into order of a field. The records are arranged in ascending or descending order (numerically or alphabetically).

If records are sorted it is much easier and quicker to find a record.

Searching Queries are used to find records which match certain conditions.

Simple query - Using one field.Eg (NAME = 'Smith')

Complex query - using two or more fields with OR, AND or NOT.Egs(NAME='Smith') AND (BALANCE > £100)(PET='Dog') OR (PET = 'Cat')(PET = 'Dog') AND NOT (Type='Spaniel')

Wildcard query - In alphabetical fields * may stand for anything.Eg (NAME = 'Sm*')will include all names starting with Sm - Smith, Smithers, Smedling and so on...

Adding new data 

A new record may be added to a file.

Eg A business may start to sell a new brand of item.

Deleting data A record may be removed from a file.

Eg A business discontinues the selling of an item.

 

The buttons used for sorting may look like these..

 

 

 

With Queries, the names of the Fields must be given as well as the data to be searched for.

 

Editing data A record in a file may be changed.

Eg If the price of an item changes.

 

File structure

A database consists of a number of related files (sometimes called tables).

A file consists of a number of related records.

A record consists of a number of related fields.

A field is a single data item consisting of a number of characters.

Example 1

This table shows a small section of a file which contains details about school pupils:

Number Surname FirstName Form

91230 Sam Fenella B

91231 Sanders Michael G

91232 Saunders Ian B

91233 Sealey Kelly R

91234 Shaw Lucy S

91235 Shaw Oliver NThe yellow section shows one record.

The file has 6 records and each record has 4 fields (Number, Surname, Firstname and Form).

The key field is used to uniquely identify a record. The key field in this example is 'Number'. No two records would have the same data in the key field.

Fields may be of a number of different types :

integer real (decimal) string (alphanumeric) date currency picture sound video a calculated field

 

When a database is created it is important that the same data is not

stored twice (this may lead to inconsistencies). This is usually done by linking the tables with relationships...using the key field of one table as a field in another table.

 

Data in a database can be accessed and used to produce reports.A report may use data drawn from a number of different files.

File Update

The data on a transaction file is used to update some of the fields on a master file.

The transaction file must be sorted in the same order as the master file.

 

This is generally done in a batch processing system where the transactions are recorded on the transaction file and later used to update the master file.

How it works (in words) :

1. A new master file is created. 2. For each transaction record, the records of the

master file are read and written onto the new master file until a matching record is found.

3. The data is updated and the record written onto the new master file.

4. When the last transaction record has been processed, the remaining records on the master file are read and written onto the new master file.

How it works (System flowchart) :

 

Here, the transaction and master files are stored on magnetic tape and used as input for the update process.

All updated (and unaltered) records are stored on the new master file.

 

Example :

A master file of stock is kept for a clothes shop. Some of the records are shown in this table :

ID Garment Price No Sold this year305 Sweater (Red) £25.00 12308 Sweater (Blue) £25.00 8309 Shorts (Size 12) £12.00 14315 Shorts (Size 14) £12.00 9316 Socks(Grey) £1.99 34317 Socks(Black) £1.99 28

The key field is the ID field.

The master file in practice would have many more fields than this ...and many more records!

Todays transactions are shown in the transaction file below....

ID No Sold today305 3309 1316 2317 1

The transaction file must be sorted in the same order as the master file (using the key field)

The resulting new master file is shown in the next table :

ID Garment Price No Sold this year305 Sweater (Red) £25.00 15308 Sweater (Blue) £25.00 8309 Shorts (Size 12) £12.00 15315 Shorts (Size 14) £12.00 9316 Socks(Grey) £1.99 36317 Socks(Black) £1.99 29

The updated data is shown in red. Note that some records will have remained unchanged.

Fixed Length Fields

A fixed length field is one which contains a set number of characters.

With fixed length fields, the fields may need to be padded out to the right length, eg with <space> characters.

eg If a Surname field is set at 10 characters then the name SIMPSON would need 3 <Space>s added on to the end of it.

Advantage - Every record is the same size, so it is possible for the computer to calculate exactly where each record starts in the file and therefore it is quicker for the computer to find a particular record.

Example 1

Each record of this file has 4 fields.

Number Surname FirstName Form

91230 Sam Fenella B

91231 Sanders Michael G

91232 Saunders Ian B

91233 Sealey Kelly R

91234 Shaw Lucy S

91235 Shaw Oliver NThe field sizes may be fixed at ...

Field Name Field Size

Number 5

Surname 10

Firstname 10

Form 1The first three records of the file would therefore be stored as in the following table (each square represents one byte):

9 1 2 3 0 S a m               F e n e l

l a       B 9 1 2 3 1 S a n d e r s    

  M i c h a e l       G 9 1 2 3 2 S a u

n d e r s     I a n               B    

                                       Each record takes up 26 bytes of storage space.

The first three records of the file take up 78 bytes of storage.

 

Floppy disks

Used for storage on microcomputers.

Usually 3.5 inches in diameter. High density floppy disks can store 1.44Mb of data.

Access to data is slower than from a hard disk.

The data can be protected by opening a small write-protect tab which prevents the contents of the disk being changed.

Floppy disks are portable and can be used for

transferring data or programs from one microcomputer to another.

backing up data from a hard disk.

Floppy disks (and hard disks) have to be formatted before they can be used.

DO NOT...

leave floppy disks in heat (eg the sun) or damp open the sliding metal thingy..it lets the dust in! touch the brown disk inside

 

 

The discs are protected by a stiff plastic cover. This has a hole for the read/write heads which is protected by a sprung metal cover.

Graph plotter

Graph plotters are used to produce high quality precision graphics usually on large sheets of paper.

They are slow, but can draw continuous curves often in a variety of colours. They are especially useful for architectural drawings, building plans and CAD (Computer Aided Design) applications, where precision drawing is required.

 

 

A mechanical arm holds a pen which can be moved across the page. The paper is sometimes laid on a flat bed (flat bed plotter) ...

...or on a rotating drum (drum plotter).

Graphics

A graphics package is used to create images.

Input may be from a mouse, light pen, a graphics tablet or a scanner. Photos from a digital camera may also be edited.

Microsoft Paint is an example of a Graphics package.

Graphics packages would allow...

creating and editing of new image choice of brushes choice of colours choice of fills freehand drawing import of images from other sources (including standard shapes) addition of text zoom options textured effects rotation of shapes

Once created, images can then be used in DTP pages or web pages.

 

Graphics Tablet (Pad)

A graphics tablet is a board covered by a touch-sensitive membrane which can detect the position of a pointing device on its surface. It can be used to -

- hold a drawing while the user traces it.

- hold a sheet of menus, icons and shapes which the user can select

A stylus (or pen) is a pointing device for a graphics tablet.

A puck is a mouse-like input device for a graphics tablet which is moved over the surface of the tablet. It has cross-hairs to position it accurately and a number of buttons for different actions.

 

Hard disks

One or more hard disks are found in the hard drive which is usually housed inside a computer. Each drive is built into a sealed unit to prevent contamination by dust and moisture.

Advantages over floppy disks :

Access to data is faster than from floppy disks. Hard discs store more data than floppy disks. (40

Gb drives are now common). They are more reliable than floppy disks as they

have more protection from dirt.

 

One disadvantage of a hard disc over floppy disk is that it is not portable - you cannot carry it round and use it on different computers.

 

The read-write head floats so close to the disk that a small speck of dust would ruin the disk. This is why the drives are sealed.

Exercise : Hard Disks

A hard drive is a sealed unit which contains one or more hard disks in a sealed case.

The advantages of a hard disk over a floppy disc are -

 (select only the correct answers) Hardware and Software

A computer system consists of hardware and software.

 

Hardware is the equipment which makes up the computer system. (If you can kick it, it’s hardware!). Hardware consists of...

- input devices such as keyboard, mouse, joystick

- the Central Processing Unit (CPU) - which does all the processing

- output devices such as a printer, monitor, graph plotter

- backing storage devices such as disc drive, hard drive

- media such as discs, tapes, paper etc

 

Software is the programs which run the system.  Be careful - a floppy disk

Access to data is faster.They can be carried aroundThey have greater storage capacityThey are less liable to damage

The main program which runs the computer system is called the Operating System. 

Other programs (called Applications programs) include ...

Word Processing programs,  Database programs,  Spreadsheet programs,  Graphics programs etc.... Computer game

 

is hardware but a program which is stored on it is software.

HCI (Human Computer Interface)

The Human Computer Interface (HCI) is the way the user interacts with the computer.

The three main types are :

Command The user types in commands.Programs use less memory.

Example : The MS-DOS interface.Type DIR /W to get a list of all the files in a directory.

Quick to operate and very flexible, but the user needs to learn all the commands and type them in correctly.

 

Menu Drop-down menus have options for selection. There may be sub-menus...

The user selects an option with either a key or a click of the mouse.

No need to learn the commands but it can be difficult to locate a particular option.

 

GUI Graphical User Interface

Also known as a WIMP (Windows, Icons, Menus, Pointers) interface.

Icons (small pictures) represent options. Colour and sound may also be used to make the interface more 'user-friendly'.

Identical icons may be used in a number of different

Detail of a GUI interface

programs. Eg a picture of a disk to save a file.

Example : Windows

Low-level IT skills needed by the user. Easy to use intuitive interface. 

 

Sound Speech driven interfaces are also now available. The user talks a command into a microphone.

Useful for...handicapped, fighter pilots, surgeons..

 

When a new computer application is being designed, decisions about which user interface is to be used are often governed by the IT skills of the user.

Experts can use a command driven interface, but those with low IT skills will need a GUI. Children need plenty of colour and sound.

All good Interfaces will have allow users to seek help if they need it.

 

Consistency of design of

interfaces is important. 

Eg The same buttons are used on a GUI for printing in each application and they appear in the same position on each display. This will make it easier for the user to learn to use the program.