Computing - F451

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  • Created by: Chloe
  • Created on: 21-04-13 16:19


Hardware - Physical parts of the computer system

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Software - Set of instructions which makes the system do something useful

Systems Software - Set of instructions that make the hardware available for use

Applications Packages - Set of intructions designed to make the computer carry out a task

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Peripheral Devices

A device that is outside of the computer processor

E.g. Printer, scanner, speakers, fax

Peripgheral Devices are one of three types;

Input Device - Data transmitted into the processor from the peripheral device

Output Device - Data transmitted into the peripheral device from the computer processor

Storage Device - Data stored outside of the computer processor, can be transmitted between the computer rocessor and itself.

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Systems Life Cycle

Feasibility Study







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Feasibility Study

Technical Feasibility - Is there the technology ready to implement the new system?

Economical Feasibility - Establish if the new system is cost effective? Will the company benifit or lose form the new system?

Legal Feasibility - Is there any conflicts? Does it comply with the Data protection Act?

Operational Feasibility - Can the company support the new system? Is there staff that can use the new system?

Schedule Feasibility - Timing, how long will it take to implement the new system> Will it stay within the time schedule?

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Analysing - Interviews

There are 4 ways of of gathering information

Interviews : (Primary Source)

     +: A lot of information in a small space of time, its quick. Specifics can be obtained. Primary Source Live chat: Email.

-: Only one person at a time could be biased. Time consuming. Some method of recording the interview (Tape the interview: good method, thorough but takes a lot of time), (Semi-Structured interview: Already have some questions to guide the interview, (Pen and paper, a lot of writing) fully structured interview: all the questions are written and only wanting the answers straight forward


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Analysing - Questionaires

Questionnaire:  ( Secondary Source)

 +: Saves time if you want to a lot of people in one go,  Potentially quicker than an interview, Style of question could make the information gathering quicker, thought through the information you might need, fixed and straight forward. Cross reference: helps reduce biased. Email: questions sent.

Open questions have one answer and are quick, closed questions do not have one answer, take a lot of time.

  -: Takes time to create a questionnaire, resources:  takes up alot of paper for a hard back copy, honesty of questionnaires are not 100%, return rates are very low.

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Analysing - Observation

 Observation: (Primary Source)

    +: Accurate, cross refernce, see it in operation; can see advantages and disadvantages of the system. You can see how the system works; the flow of the system. Can see where the problems are.

-:  Can take a lot of time, a lot of people need to be observed.  Could be a problem with the user.

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Analysing - Documentation

Documentation: (Secondary Source)

+: Identify clear data that is documented in the system. Website; easy to read and be found. Email; sent a document.

  -: May miss some documentation; not all documentation can be found. Hard to understand what the documentation applies. Observation needs to be linked to documentation to ensure results.

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System Flow Charts

A diagram that shows how the elements of a system are associates with each other and how the y interact with each other.

- Types of hardware

- Direction of the flow

- Inputs and outputs of the system

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Input Design

Data depends on a number of factors

- The data that is required - graphical/text/image? Is it already there?

- Hardware available - keyboard, automatic?

- Experience of operator

- Design of user interface

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Output Design

Presented in a way that is appropriate. Dependant on the factors of input

Data Structure Design

- Needs to be stored somewhere

- and then retreived


- System must be considered succesful

- Must match certain criterea

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- Requirements specification - list

- Design specification - Stages

- Programme Specification - Algorithms

- Technical Documentation - Programme and details, hardware

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Stock Control

- Details of induvidual items

- When something is bought the stock decreses

Order Processing

- When a stock of something falls below the limit an automated oreder will go out to the supplier and the order will be placed

Pay roll

-Batch Process - Records Kept

Process Control

-Automatically controls the process

-Computer recieves the information about processors

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Point of sale systems

3 Actions

-Goods being Bought

-Carry out processing and output

-Arrange for payment

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Marketing - CAD CAM

- Customer Awareness

CAD (Computer Aided Design)

- Uses od a computer that designs a commoditiy

- Solutions

- Calcuations

- Predictions

CAM (Computer Aided Manufacture)

-Manufacturing process

-CAD and CAM together provide a seamless process

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Marketing - CAD CAM

- Customer Awareness

CAD (Computer Aided Design)

- Uses od a computer that designs a commoditiy

- Solutions

- Calcuations

- Predictions

CAM (Computer Aided Manufacture)

-Manufacturing process

-CAD and CAM together provide a seamless process

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Marketing - CAD CAM

- Customer Awareness

CAD (Computer Aided Design)

- Uses od a computer that designs a commoditiy

- Solutions

- Calcuations

- Predictions

CAM (Computer Aided Manufacture)

-Manufacturing process

-CAD and CAM together provide a seamless process

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Applications Software - Apllications Package

A programme that does a task that would have to be carried out even if there was no computer

Applications programme together with associated documentation

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Generic Applications - Software, Programmes, Packa

Solve a number of problems

- Word processor


-Desktop Publishing (DTP)

-Presentation Software

-Drawing Packages

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Custom Written Packages

+ - For Specifics

 - Unique

 - For your needs

- - No support

 - no guides

 - could have a problem - hard to fix without support online or a specialist

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Knowledge Based Sytstems

4 Areas

Knowledge Base - Where all the knowledge is kept - experts enter their knowledge

Algorithms - Problem solving area

Set of rules - so that the system knows what to do

User interface - so that the user can use the system easily and get and give information to figure out the problem

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Operating Systems

User  ---------> OPERATING  <----- Programmer

Applications ---> SYSTEM <------- Package

Operating System - Controls operations of hardware

-Provides a platform for the applications

-Provides means of communication between the outside world (humans) and the computer

-Controlsa acces to system - passwords, files, rights

-Peices of software - Antivirus - UTILITY SOFTWARE

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Batch Processing

Used when -

- Large amounts of data need to be processed

- Data is similar in nature and processing

- The computer has indetifiable times when it is not being used , so has available processor time

- The application does not require human intervention

-Can wait - does not have to be immidiate

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Real Time

Control of in real life of imformation handling

eg. Video - you want to watch it there and then

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Single User

One user on the computer

-Their programmes at one time

-eg. At home - only one user on the computer at one time

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Multi - User

More than on user on the computer simultaneously

Two types of multi user OS

- Network System - Computers linked together for purposes of compunication and sharing rewources - Normaly - one machine controls the rest

 - Time - Sharing system - Single Computer connected up to a number of terminals

-allows communication between users and sharing of hardware and software across the system

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Multi Tasking

Allows several applications to be available simultaneously. They all run at the same time all being done at the same time

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Allows software and data files to be distributed around a system

Speed acces to files

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User Interface

The means of communication between the user and the machine

Human Computer Interface (HCI) - Different types of HCI

Form Based - Form on screen to be filled in

-Propts the operator to ask each of the questions in turn

-Makes the operator input info in correct order and format

-Makes checking information easier

Menu Based - Operator usually does not know the options - eg. information for tourists

handsets menus for tv's

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User Interface Cont. - HCI

Graphical User Interface (GUI)

- Or WIMP- Windows, icons, menus, pointers

-What the user sees on the screen

-Used by most people

Natural Language

-Computer asks a question which makes a response (from the user). Then the user thinks they are talking to the computer

Command Line

- Command prompt

-Series of commands that tell the computer what to do

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-Data Transfer programmes

-File Handling


-Back up


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ASCII - character set for the computer to understand you

EBCDIC - Developed from IBM - Different codes form ASCII

UNICODE - 10 bit code - over 65000 characters

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Automatic Data Collection

Computer collects data through sensors in the outside world

- These give info on the physical environment

eg. Bar codes, OMR, MICR, Scanners, Voice recognition, chip and pin, image capture, video capture, camera

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Manual Data Entry

Data entered by a human via keyboard

eg - touch screens, OCR, keyboards

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Validation - Verification

Validation - Double entry

- Visual Check

Validation - Range Check

-Existence Check

-Character Check

-Prescences Check

-Format Check

-Check Digit

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Forms of output

- Graphs



-Interactive presentation




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Back Up -Archiving

Back Up

-Copy of data on a secondary storage devices - usually somewhere away from the original device


-Data put somewher else that is not in use

eg. Yr 12 meritsystem for yr 10

Not on the original file system but can be revisited

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CPU (Core Processor Unit)

Control Unit - Instructions - Decide what to do then go and get it

-decipher the instruction - work out then carry it out

- tell other parts to carry out instruction

ALU (arithmetic logic unit)

- Does all the arithmetic and logical decisions and makes them, adds numbers

- Acts as a gateway between the processor and the other parts of the computer

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CPU cont. - Memory Unit

Where everything the processor is going to use is stored

-including the programme instructions

-data to carry out instructions

-find info stored

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PC - Programme counter

- Keeps track of where everything is in the computers memory

CIR - Current Instruction Register

- Holds instructions that need to be executed while it is being done

MAR - Memory Address Register

- Holds the position of the next peice of information

MDR - Memory Data Register

- Acts like a buffer - holds anything that is copied from the memory ready for the processor to use


In arethmitic unit - holds the results

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Data Bus - Used to carry the data that needs to be transferred from one part of the hardware to another

Control Bus - Controls and co-ordinates the operations of the rest of the processor

Address Bus - Carries the address of the location which the data in the data bus should be delivered

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Connectivity of devices

Physical - Hardwire

- Ethanet - CAT6 - Fibre Optic

Non - Physical - Wireless

- Routers - USB wireless cards - Netwrok Cards

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Primary Memory

ROM (Read only memory) - Data saved onto the ROM  - It cannot be changed or removed by switching off the computer - eg. Processors

- Operating System is stored on the Hard drive - When needed a bootstrap is sent out to 'boot' the operating system to the ROM

RAM (Random Acces Memory) - Saved temporarily on the RAM will be deleted when the power is off

- Stores programmes that are in use (including Operating System)

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Secondary Storage

Magnetic Tape - Archiving and large file back up

Magnetic Hard Disk - Data stored useing small areas of disk which are magnetised to one of two states - One standing for 0 and the other 1

CD ROM - optical storage drive - optical meaning reflection of laser to create the data - transpot of files

DVD ROM - same as CD's buut can hold larger amounts of information

Solid State Drive -  USB/Wands/Cards - Transportable and small

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Buffers and interrupts

Primary Memory <-------> Secondary Storage

Primary Memory <------> ALU <-----> Secondary Storage


The problem is caused because the secondary storage device is slow compared to the processor solution

- Put small amount of fast memory into the system between the ALU and the secondary storage device

- Processor can send data very quickly (or recieve) then do something else while the storage takes time in sending thedata. The small amount of memory between the two parts of the system is called a buffer

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Buffers and interrupts cont.

Stage one - filling the buffer from the processor

Primary Memory <---> ALU <--->Buffer   Secondary Storage

Stage two - emptying the buffer to the secondary storage

Primary Storage <--> ALU   Buffer <----> Secondary Storage


If there is more data in the buffer a message will be sent to the processor ( well control unit) that the data hass all gone from the buffer.

Becasue this message from the secondary storage makes the processor stop what it is doing it is called an interrupt

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Peripheral Devices

Communication Devices

Storage Devices

Input Devices - Keyboard - Mouse - Scanners - Graphocs Tablet - Barcode Readers - MICR -Microphones - OCR  -OMR  - Touch Screen

Output Devices - Screens - Touch Screen - Printers - Speakers - Fax

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WAN - computers can be linked together to form networks

- If the distances are short the network is called a LAN, if longer the network is a WAN

- Networks allow computers to communicate

-netwroks allow the sharing of both hardware and software

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-Each computer needs to be able to communicate with others

- Connected in someway

- With a number of computers attatched to the network, gonna get complicated - control signals - jobs

- set of instructions

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Data Transmission

Serial - Only one wire - Data is transmitted in the form of bits down the wire, so an 8 bit byte that stands for a sinlge character will be transmitted in 8 parts one single for each bit

Parrallel - Connected by more than one wire - more bits can be sent at once

- usually 8 wires or more - faster

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Modes of Transmission

Simplex Mode - One way - eg. keyboard - mous

Transmitter -----> Reciever

Duplex Mode - pass both ways at the same time - eg. internet, phone line

Device 1 <------> device 2

Half duplex - can go both ways but not at the same time - eg walkie talkies

device 1 <- - - - - Device 2


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Methods of cerrecting errors in data transmissing

Echoing Back - Send 1st - send back - if correct when compared to 1st (original) then correct

Parity Check - Data sent in 0's and 1's - must always be either odd or even number - devices decide - odd number 1's sent, even recieved data is asked to be sent again

Check Sum - add all the bits together - if the answer is the same as the original then correct if not the sent again

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Packet Switching

- Equal sized packets - labelled - if cant go to the place written on label then finds another route to get to it - reassemblled at the end

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Cicuit Switching

Route is chosen - It is in one peice

- directly sent to the designated route

 - takes up space

 - low security

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A set of rules that need to be set up in order to allow transfer of data to be carried out

Physical protocols: -Serial, Parallel, duplex, half duplex or ethanet

-Frequencies used in a wireless network

-Rule of finding means of connection

-Connection between devices - hardwires etc.

Logical Protocals: -A set of rules the data has to follow (eg http,baud rate)

-The form the message takes

-Parity checking: checking data to be correct


-Spotting errors in data transfer

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