Standard-Grade-Computing-Revision-Notes-FGC by xiaopangnv


									                                          S4 Revision Notes

                                        General Purpose Packages

Data Types: there are many different types of data: Text, Numeric, Picture (graphic), Audio,
Photographic, Animation, and Video

Standard File Formats: These make it possible to transfer data between different types of package.
Two common text formats are ASCII that stores text as plain characters and RTF that maintains the
format of the text

HCI: Human Computer Interface. This is how the user and the computer interact

User Friendliness: this is the term that refers to how easy it is to use a package

Menu Driven: this is using software through menus

GUI: Graphical User Interface. This is controlling a computer through the use of small graphics called
icons. The type of GUI we use is a WIMP system

WIMP: Windows, Icons, Menus, and Pointers. A wimp system uses graphics and menus to allow the user
to control the computer. It is a very user-friendly system

Keyboard Shortcuts: These can be used to carry out tasks more quickly e.g. you can print by pressing
Ctrl and P together

Customising the HCI: The HCI can be changed by the user to suit their own requirements

                                           Integrated Packages

Advantages Of Integrated Packages:
    Cheaper to buy than buying separate packages
    They have a common HCI
    Data is transferred easily between different parts of the package

Disadvantages Of Integrated Packages:
    They may not have the same range of functions as stand alone packages
    You might not want to use all the packages, therefore can be more costly than necessary
    They take up more memory space than a stand alone package

On-Line Help: help is available within the program through a menu. You can get help while still using the
package. People that are familiar with the package use it when they need some help on a certain topic.

On-Line Tutorial: this is help for beginners. Tutorials take them through the package step by step
showing them the basics of the program. Once completed the user should be able to start using the

Template: this is the skeleton of a document that is already laid out for you to use

Wizard: this is a piece of software that takes you through a task step by step. They are useful for people
who need help completing a task or when complex tasks are to be performed

Static Linkage: when data is transferred between packages a link is created. When using static linkage
the link is broken after the data has been transferred. If a further change is made to the original data, the
new data will not change – Copy and Paste is an example of static linkage

Based on original notes by Mr J. Durkan, Hillpark Secondary School                                              1
Dynamic Linkage: dynamic data linkage allows data to be transferred between packages, however once
data has been transferred a link remains between the transferred data and the original, meaning that if
data changes in one package it will automatically be updated in the other – Creating a graph from
spreadsheet data is an example of dynamic linkage

                                              Word Processing

Advantages of a word processor are:
      That text can be edited
      Can use features like search and replace and spell check
      Text can be formatted e.g., underline, bold, italics, line length, page length etc.
      As many printouts as required can be made
      High quality of output

Dedicated Word Processor: this is a machine that can only do word processing.

Word Wrap: this is when the computer automatically takes a new line when the word will not fit on the
present line. The whole word is moved to the next line

Spell Check: this is a feature of a word processing package that will check the spelling of a document
and highlight words that do not appear in the computers dictionary. The user can ignore the word
highlighted, choose an alternative from a given list or add the word to the dictionary. Limitations of a spell
checker is that it will not recognise words not in the dictionary, it will not correct grammar mistakes, it will
not recognise the wrong use of words e.g. there, their

Grammar Check: Similar to a spell checker, but highlights what it thinks are grammatical errors

Search and Replace: this is a feature of a word processing packing that allows the user to replace one
word with another throughout a document. The user simply keys in the search word and the replacement
word, then chooses to carry out a replace all (global change) or one word at a time (selective change)

Tabulation: this is a feature of a word processing package which allows the user to set markers to lay out
text neatly in a table

Header/Footer: These have to be typed only once, but headers will appear at the top of every page in a
document. Footers appear at the bottom of every page and may contain page numbers, date etc.

Standard Paragraph: this is when the same piece of text is required again and again. The text is stored
on disc and inserted into documents when needed.

Mail Shot: this is when letters are prepared by mail merge (using a word processor and a database) and
sent out to individuals on a mailing list – also called junk mail.

Standard Letter: a standard letter is one that is created and saved for future use. When required
personal details can be added, such as name and address, before sending

Mail Merge: this is linking a word-processed letter to a database file and merging the personal details
from the database into the WP letter, allowing each letter to be personalised.

OCR: Optical Character Recognition. This is a printed WP or typed document that has been scanned into
the computer and translated into an electronic form allowing it to be edited. It saves the time of re-typing.

Based on original notes by Mr J. Durkan, Hillpark Secondary School                                             2

Database: a database is a package for storing information. All information held is called a file.
Information held on one person/subject is called a record and information on one category is called a

Adding a Record: if more items are to be included in a database, it is possible to add records.

Adding a Field: if extra categories of information are to be added to a database, it is possible to add

Searching A Database: this means looking for specific information within a database. There are 2 types
of search: simple search, searching on one field only or complex search, which is searching on two or
more fields.

Complex Search: A search on more than one field. If asked to do a complex search question, always
name the fields that are to be used and also the data to be entered into those fields.

Sorting A Database: this is putting the database in to an order. Sorting can be numeric or alphabetic. It
can also be ascending or descending. A database can be sorted in 2 different ways: simple sort on one
field only, or complex sort on two or more fields.

Alter Record Format: this is displaying the record in different ways. We can view many records on the
screen at the same time in a column (list view) or a single record at one time (form view).

Computed Field: this is a field that carries out a calculation based on information from other fields in the
same record. The calculation takes place automatically.


Spreadsheet: this is an application package used for calculations. A spreadsheet is made up of rows
and columns. These rows and columns combine to form cells.

Row: this goes across the way. A number identifies each row.

Column: these go up and down and are identified by a letter.

Cells: cells are where the row and the column meet and they are identified by the column letter and the
row number, e.g. A1. Cells can contain text (labels), values (numbers) or formulas (calculations).

Column Width: The column width can be increased, to allow space for details. It can also be decreased.

Cell Attributes: cell attributes are used to change the appearance of cell. They can show currency (the
£ sign), decimal places, bold, centred etc.

Insert Row/Column: if information has been missed out of a spreadsheet a new row or column can be

Charts/Graphs: information from a spreadsheet can be presented as a chart or graph; this is a picture
view of the information in a spreadsheet, which makes it easier to read and understand.

Formulae: most formulae in spreadsheets are simple
       =A1 + A2 (add 2 cells)
       =A1 – A2 (take one cell from another)
       =A1 * A2 (multiply 2 cells)
       =A1 / A2 (divide one cell by another)

Based on original notes by Mr J. Durkan, Hillpark Secondary School                                             3
Sometimes the formula may be more complex, e.g. to add together a range of cells, or to find the average
of a range of cells
         =SUM(A1:A10) (adds together all cells in given range)
         =MAX(A1:A10) (finds maximum value in given range)
         =MIN(A1:A10) (finds minimum value in given range)
         =AVERAGE(A1:A10) (calculate the average of all the cells given)

Conditional Formulae: more complex spreadsheet formulas can involve conditions. This means that a
cell will take on one value if a certain condition is true and a different value if it is false.
            =IF(C2<C3,”True”,”False”)
            =IF(C2<C3,B12*0.15,””)

Replication: Replication just means copying. If the same calculation is to be carried out in several cells,
replication could be used. This is copying and pasting a formula in a spreadsheet. There is a small black
box at the bottom right of the cell that can be clicked and dragged to replicate a formula.

Relative Replication or Referencing: this happens when we copy a formula and the cell references
automatically change depending on where it is copied to. For example if =A1+B1 were replicated down a
column it would automatically change to =A2+B2…etc.

Absolute Replication or Referencing: this is replicating a formula into a cell and not having the
formula’s cell references change. In order to do this, a $ sign is needed before the references you wish to
stay the same. For example if =A1+$B$1 were replicated it would change only half the formula to
=A2+$B$1, leaving the cell B1 constant. (A useful example would be if a particular cell contained the
current rate of VAT and you wanted to refer back to that cell to calculate the VAT on other cells)

Cell Protection or Cell Locking: this is locking the cells so that their contents cannot be changed
unless a password is given. Cells that contain formulas are often locked


Graphics: this is an application package that allows the user to create and edit images

Graphic Tools: these include a pointer, box, circle, line, fill colour, line colour

Rotation: this is turning a graphic around, either freehand or a fixed number of degrees.

Scale: this is making a graphic bigger or smaller, but maintaining its shape. Dragging from a corner grab
handle allows us to do this. Dragging from a centre grab handle distorts (squashes or stretches) the

Group: this is locking more than one graphic in a picture together. This is done so that when you move
the graphic all grouped parts move together.

Change Attributes: this is changing the style of the tool, e.g. the thickness of the line tool, the colour of
the fill tool etc.

Scan Graphic: this is using a scanner to get a picture from paper into a digital format on a computer.

Crop Graphic: this allows you to select a certain part of a graphic so that it can be retained and the rest
of the graphic discarded.

Hard Copy: this is a print out of your document.

Based on original notes by Mr J. Durkan, Hillpark Secondary School                                              4
Back up: this is a second copy of your data stored in a different location. We keep a back up in case
something happens to the original.

                                             Expert Systems

Expert System: this is a program that can imitate the abilities of a human expert in a small area of
expertise. They address problems normally thought to require human specialists.

Areas Covered: legal advice, medical diagnosis, car diagnostics.

Advantages of Expert Systems: they allow us to keep, reproduce and share expertise that is difficult or
expensive to obtain. They can give advice leaving human experts free to do other things.

Disadvantages of Expert Systems: They cannot be completely relied upon to make important decisions
since, in the end, they are just programs

                                           Desktop Publishing

Desktop Publishing: a desktop publishing package allows inexperienced users to create high quality
documents, such as magazines, newsletter, posters etc. They combine features found in word
processing packages and graphics packages. Their main advantages are that they give the user good
control over the layout of the document. Text or graphics are often imported from other packages.

Import Text: Text is often created in a word processing document and imported into the publishing
package where it can be manipulated.

Text Wrap Around Graphic: This feature neatly places text around a graphic conveniently for the user.

                                     Presentation And Multimedia

Multimedia: this means combining different types of media, such as text, images, sound and video to
present information.

Creating A Presentation: presentations can be made easily using a template or they can be started from
scratch in a blank presentation.

Adding Information: many different types of data can be added to a presentation, text, graphics,
numeric, audio, video, animation etc.

Hyperlinks: individual slides or pages can be linked together in a chosen order. To do this we use

Capture Audio & Images: this is the user recording their own sound clips to add to the presentation or
using a digital camera or scanner to add their own pictures or video.

                                           Web Page Creation

Web Page: a web page is a page that is created using a special language. Web pages can be viewed on
a network or the Internet. A web page can contain many types of data, like a presentation package.

Based on original notes by Mr J. Durkan, Hillpark Secondary School                                        5
Navigation: moving from web page to web page is easy; we use hyperlinks to do this. Many different
items can be a hyperlink, such as text, pictures, and animations. The back and forward buttons on a
browser can also be used to navigate from page to page.

Add Table: Most web pages use tables to hold the text and graphics where you want them. The table
can be made invisible if required.

Hotspots: this is an area of a website that has an action attached to it, so when the mouse is moved over
it something will happen.

                               Electronic Communication And Networks

Networks: a network of computers is when 2 or more computers are connected together by cabling so
that they can communicate. There are 2 types of networks, LAN and WAN.

LAN: Local Area Network. This involves computers being connected together over a small distance e.g.
a room or building. The advantage of LAN’s is that they can share data and expensive peripherals
(devices). They allow computers to communicate via e-mail. These computers use wires or wireless
communication to link together.

WAN: Wide Area Network. This involves computers being connected together over a large distance e.g.
a city, country or worldwide. Computers are linked together mainly using telephone lines and modems or
routers. The Internet is a WAN.

Internet: it provides up to date information. There are large amounts of information available on the
Internet for users to access and it is very fast.

Browser: this is a piece of software that allows us to view the Internet. The browser we use is Microsoft
Internet Explorer.

ISP (Internet Service Provider): An ISP allows customers access to The Internet via their host
computer. They charge the user for this service. Examples of ISP’s are AOL and BT Total

Internet Ready Computer: this is a computer that has a built in modem and ISP software already
installed when you buy it.

Dial Up Connection: this is accessing the Internet over the telephones network. It is a slow way of
accessing the Internet and the user is charged per minute they are on-line.

Broadband Connection: this is a permanent connection to the Internet where the user is always on-line.
It is a faster connection than dial up and users pay a set monthly fee.

Search Engine: this is a tool available on the Internet that allows users to search for specific information
by typing in keywords. Google is a search engine.

Software Download: this is taking information from the Internet and saving it on your computer. The
information that is being downloaded is transferred from another computer somewhere in the world.

Software Types: software that is downloaded is of 3 types:
     Freeware software- can be downloaded and used free of charge
     Shareware software- can be downloaded and used free of charge for a trial period, then a small
       fee has to be paid for continuing to use it
     Commercial software- this involves having to pay the full price for software before it can be
       downloaded and used.

Video Conferencing: this involves two or more people at different locations being able to communicate
over a network so that they can see and hear each other. Each user requires special hardware and video
conferencing software to allow this to take place.

Based on original notes by Mr J. Durkan, Hillpark Secondary School                                             6
Mobile Internet Technology: this is accessing the Internet without needing a phone connection. It can
be done in many ways including using mobile phones or PDA’s (Personal Digital Assistants). The devices
usually access the Internet wirelessly using WiFi or Bluetooth connections

E-Mail: this is sending messages over the Internet or a network. Email is a very quick and cheap way of
sending messages to anywhere in the world. To send or receive email the user must have access to a
network and an email address. The disadvantage to email is that it is not a very secure way of sending
data, since email can be hacked into.

File Transfer: this is the sending and receiving of files over a network. One way of doing this is by
attaching it to an email.

Attachments: this is sending files on a LAN or over the Internet. The file is linked to the email and is sent
to the recipients email address.

Netiquette: this is the term that describes how we should behave while using a network. It has rules of
how we should talk to other users, and other handy hints.

Text Messaging: this is sending a short message to someone using a mobile phone.

On-Line: this means being directly connected to a computer, a network or the Internet

Off-Line: this means not being directly connected to a computer, a network or the Internet

Multi Access: this means many users having access to the same information or software at the same

NIC: Network Interface Card. For a computer to work on a network it needs to be fitted with a network
interface card. An NIC allows the computer to connect to the network.

Clients: when a computer is connected to a network it can act as a client or a server. A client is a less
powerful machine that relies on servers for saving work, printing, accessing the Internet and so on.

Servers: These are more powerful computers on a network that supply the clients with the files and
services they need. There can be many different types of servers on a network all doing different jobs e.g.
file servers, print servers, Internet servers, etc.

                                    Implications Of Using Computers

Social Implications: these are issues that affect people in their daily lives and at work.
    Traditional jobs have now gone and staff may lose jobs or have to be re-trained to use the new
    Working conditions have improved as the use of computers makes many peoples jobs easier and
        more satisfying.
    It is now possible for people to work, shop and bank from home and use networks and the
        Internet to contact people around the world

Economical Implications: this is to do with the costs involved in new technology.
    Initial Costs – this is setting up a new computerised systems - buying all the hardware and
      software and training staff. This can be very costly.
    Running Costs – these are costs that are ongoing once the system is set up. Examples include
      the cost of electricity, paper, ink, disks, cartridges etc.
    Staff Costs – paying the staff to work

Security And Privacy Issues: this is a very important factor to consider when using computers.
    People have the right to see what information is held on computer about them and companies
       must make this information available to people when asked
    Problems can arise if information becomes out of data and is still used

Based on original notes by Mr J. Durkan, Hillpark Secondary School                                          7
       Security measures have to be taken so that companies can be sure that the data they hold
        cannot be stolen or misused
       There is a law, The Data Protection Act, that covers how companies use data and what they must
        do to ensure that they do not break the law

Data Protection Act: This law protects the rights of the individual. It governs the way in which data is
collected, stored and processed by a company. The person who has data held about them is called the
data subject. The person who is using the data is called the data user. The person in charge of the
company storing or processing data is called the data controller. If any company wants to hold data they
must first register with the Data Protection Registrar. There are eight principles, which companies should

Computer Misuse Act: this act makes hacking and the spread of viruses illegal. Hacking is trying to gain
access to a computer system without permission.

Copyright, Designs & Patents Act: this act covers the use, buying, selling and downloading of material.
It gives the creators of software rights to control their material and specify how it should be used.

                Automated Systems - *** NOT IN PRELIM – ONLY IN FINAL EXAM ***

Automated Systems: an automated system involves a computer controlling a sequence of events
without requiring human intervention

Reasons For Automating: there are 6 main reasons why many companies have now automated their
      Speed – automated tasks are carried out more quickly than previous methods, so more tasks
         can be done
      Hazardous Environment – machines can do jobs in places where it is unsafe for a human to
      Repetitive Tasks – humans get bored carrying out the same task again and again, machines do
         not. This means that they are less likely to make mistakes
      Accuracy – an automated system can produce exactly the same item many times without any
         differences, humans would get tired and make mistakes
      Efficiency – an automated system is more efficient than humans as they work faster, are more
         accurate and they do not need time off. They can work 24/7
      Adaptability – machines can easily be reprogrammed to do different tasks and can have
         different tools attached to them quickly

Sensors: Sensors are used to pick up information from their surroundings. The computer analyses this
information and uses it to control motors, machines or robots.

Motor: Each robot joint has a motor to control its movement

Interface: this is hardware situated between a device and the processor. It is used to compensate for the
differences in speed and operating characteristics of the device and the computer.

Analogue And Digital: an analogue device can give a wide range of signals. A digital device only
generates 2 values, on or off (1 or 0). A computer only uses digital data, and most connected devices are
analogue devices, so normally the signal has to be changed

Analogue to Digital Converters: these are devices used to change an analogue signal into a digital
format. Feedback from a sensor to a computer would require analogue to digital conversion

Digital to Analogue Converters: these are devices used to change a digital signal into an analogue
format. A computer sending instructions to a robot would require digital to analogue conversion

Based on original notes by Mr J. Durkan, Hillpark Secondary School                                           8
Input Sensors: there are many types of sensors e.g. heat, light, movement, sound and pressure

Feedback: this is the return of information from a sensor to the computer. The sensor monitors its
surroundings constantly feeding information back to the processor

Robot Anatomy: This is the parts of a robot. It has similar joints to a human e.g. waist, shoulder, elbow
and wrist and some sort of tool attached

Embedded Systems: this is a computer inside a device that is dedicated to do a specific task.

Intelligent Robots: this is a robot that can make decisions, learn from mistakes and adapt to different

Stationary Robots: these are robots that do not move; they are fixed in the one position.

Mobile Robots: these are robots that can move around a factory, they are powered by motors and move
using wheels or tracks.

Light Guidance: the robot follows a path marked out by a line painted on the floor. A light sensor
(camera) is used to detect the line. If the line gets dirty the robot might not detect the line and it will stop

Magnetic Guidance: the robot follows wires buried under the floor. A magnetic sensor is used to detect
the wires. This is a very accurate way of moving a robot around, however if the path has to be changed
then the wires have to be dug up and re-laid.

Programming Robots: a conventional program can be written that tells the robot exactly what has to be

Lead Through Process: a skilled human operator uses a tool and a computer records their movements
and it uses this information to control a robot to make the same movements as the human

Control Languages: this is how the operator gives instructions to the robot. There are many different
types of control languages. Control languages are high-level languages normally stored in ROM. They
are stored in ROM since ROM software can’t be accidentally deleted and also loads very quickly. Control
languages use special commands to control robot movement e.g. move, grasp rotate etc

Real Time Processing: this is where events are processed exactly as they happen. The output from the
computer depends upon the input from sensors that are constantly monitoring their environment. Real
time processing is used when a fast response is crucial e.g. nuclear plant, autopilot in a plane

CAD: Computer Aided Design. This is using computers to design and plan products. Once they have
been designed they can be viewed from many different angles, giving a real life view of the product. It is
easier than creating it by hand and much quicker to produce multiple copies.

CAM: Computer Aided Manufacturing. This is creating products using a computerised process. It
involves machines controlled by computers to cut and shape the object e.g. lathes

Simulation: this is the use of a computer system to mimic a complicated activity in real life. Simulation
allows a process to be studied safely at a reasonable cost.

Virtual Reality: this is a type of simulation. The user enters a ‘virtual world’ where their movements are
translated into screen changes by a computer. VR uses sensors fitted to headsets, data gloves etc that
respond to user movements and can be translated into screen output making the environment seem very
realistic to the user.

Social Implications: these are changes that affect the users of the systems. Some social implications
      Employment Changes - jobs have changed with the introduction of robots. Staff have to be re-
        trained to control the robots rather than do the tasks themselves
      Some staff could lose jobs

Based on original notes by Mr J. Durkan, Hillpark Secondary School                                                 9
       Staff could have more exciting jobs so they are less likely to become bored. They also could
        have more leisure time as their jobs are less intensive

Technical Implications: these are changes in the technology and the layout of the factory.
    Safety - Robots can be dangerous, so safety precautions have to be taken to make sure humans
       working with robots are safe. Robots have many safety features built into them, like bump
       sensors, warning lights and sirens, or are programmed to move slowly
    Factory Design – Factory layouts have changed to meet the needs of robots as well as humans.
       Should areas where robots are working be cordoned off? Can robots and humans work safely in
       the same area? Is there enough room for robots to manoeuvre?
    Systems Analyst – a system analyst is needed to plan and carry out the technological changes to
       the factory. They must decide what areas can be automated and oversee the changes. Once
       the factory is up and running, the systems analyst is responsible for monitoring the running of the
       system and to iron out any problems

Economic Implications: The initial cost of automation is very high but over time this will be reduced and
eventually bring huge profits for the company
    Out going costs are: Re-building the factory, buying and installing the robots and their computer
       systems, retraining of employees, replacing and repairing broken parts
    Savings are: No need for human wages, heating, lighting, canteens, toilets etc and the fact that
       the robots will function 24 hours a day

                                            Computer Systems

Software: the instructions given to a computer telling it what to do.

Hardware: the physical parts of the computer system.

Program: a complete set of instructions.

Data: the information that the user enters into a program/computer.

Machine Code: this is the language a computer understands. It is made up of 1’s and 0’s. It can also be
known as binary code or object code. Machine code is not portable – will only work on the computer it
was created for.

High Level Language: this uses words similar to English, that are easy for humans to understand and to
write, but has to be translated into machine code for computer use. High-level languages are portable.

Translator: these are programs that are used to turn a high level language into machine code. There are
2 types of translators, compilers and interpreters.

Compiler: this type of translator takes the program code, as a whole, and translates it into machine code
in one operation. Once it has been translated into machine code it is known as object code. This object
code can be saved as a file and can be run directly, meaning that there is no need for further translation
unless the program has to be changed. A compiler takes just as long as an interpreter to translate the
program, but once it has been translated, it runs the program more quickly than an interpreter, since
translation is no longer required

Interpreter: this translator takes the program and turns it into machine code one line at a time. If an error
is present in the line it will be highlighted immediately. This means that an interpreter is useful when a
program is being written for the first time, since it will help the programmer to identify errors. Every time
the program has to be run it must be re-translated. An interpreter runs programs slowly, since it translates
every time the program is run.

Software Portability: Portable software is software than can be taken to a different type of computer
and/or operating system and run with little or no change

Based on original notes by Mr J. Durkan, Hillpark Secondary School                                        10
The Operating System: this is a set of programs that allow the computer to run efficiently. Everything
that happens in a computer is under control of the operating system.

Functions Of An Operating System: the operating system has 5 main functions:
    Memory management – controls where programs are stored in memory
    File Management – organises the saving and loading of files sent to backing storage
    Input/Output – controls the reading of data from input devices and the sending of data to output
    Job Scheduler – organises the order in which different task are carried out
    Error Reporting – informs the user of any problems

Interactive System: This involves a two-way communication between the user and the computer e.g.
using a cash machine, word processor or playing a computer game

Background Processing: this involves the processor doing a job ‘in the background’ while carrying out
another task e.g. printing a document while the user types up a new one.

Types of File: A file can be a program file or a data file. Think about using a database package to
create a file containing customer names, addresses and phone numbers. The database software is the
program file. The file of customer details is the data file. The data file needs the program file to access it.

Device Driver: Every device attached to a computer system needs special software so that it can
communicate properly with the computer. This software is called a driver program e.g. to print properly
from a certain computer, a system needs to have the correct printer driver installed

Hierarchical Filing System: Most modern computers now use hierarchical filing systems. This allows
the user to create a hierarchical structure with folders within folders. It means that they can organise their
work so that it is easy to find. The same file name can be used for different files as long as they are in
different folders

Bit: a binary digit, either 1 or 0.

Byte: a group of 8 bits.

Kilobyte: this is 1024bytes.

Megabyte: this is 1024 Kilobytes

Gigabyte: this is 1024 Megabytes

Terabyte: this is 1024 Gigabytes

Input Process Output: this is the way a computer system works, input is given, a process is carried out
and output is provided.

CPU: Central Processing Unit. This is where all the processing takes place; it is split into two main parts,
the processor and memory.

RAM: Random Access Memory. Data stored in RAM is not permanent; it is lost when the computer is
switched off. Data held in RAM can be changed.

ROM: Read Only Memory. Data stored in ROM is permanent, so it cannot be changed.

Word length: this is a collection of bits that is treated as a single unit by the processor. E.g. if a computer
has a 32 bit word length it means that that it can handle data in 32 bit chunks. It can read from memory,
process and write to memory 32 bits at a time

Addressability: an address is associated with a single storage location in memory. Each location has its
own unique address. The term addressability refers to the way each location is uniquely addressed and

Based on original notes by Mr J. Durkan, Hillpark Secondary School                                          11
Registers: these are temporary storage areas within the CPU that are used by the processor as it carries
out its various tasks

Control unit: this controls the order and timing of all events within the CPU

ALU (Arithmetic and Logic unit): Carries out calculations and decisions within the CPU

Storing Numbers: Integer numbers are converted and stored as their binary equivalent. Each binary digit
represents a power of two. Below is a table that highlights how digital numbers are translated into binary.

Place value             16                8                4                  2                       1
Binary                   0                1                1                  0                       1
This is the decimal number 13 ( 8x1 + 4x1 + 1x1). So decimal 13 is stored as 1101

Storing Text: Each character (letter) takes up one byte of memory. It is stored as a unique 8-bit binary
code. This code is called the ASCII code e.g. the letter A is stored as 01000001

Storing Graphics: Screen graphics are made up of pixels (The tiny dots that make up the screen). Each
pixel on the screen is stored in 1 bit of memory. If a pixel is shaded the memory bit is set to 1, and if not
shaded the bit is set to zero. The higher the resolution of the image, the more screen pixels it will use,
so more memory will be required to represent it.

Storage Requirements: to calculate the storage requirements of a black and white pixel graphic you
multiply the number of pixels vertically by the number of pixels horizontally, this will give you the storage
requirements in bits. This can then be divided by eight to get the answer in bytes.

Control Characters: these are characters on the keyboard that control various functions. They are non-
printing characters. Examples of control characters are return key, line feed etc.

Character Set: this is the total set of characters that a particular computer system uses and can
understand. Different countries use different character sets due to different languages.

Sequential Access: This involves having to read from the start of a file to get to the data that you want.
So it can be a slow process. Magnetic tape is a sequential device.

Direct (Random) Access: This method can go straight to the data being searched no matter where it is
stored on the file. It is much faster than sequential access. A hard disc is a direct access device

Mainframe: a large powerful computer serving hundreds, even thousands of users.

Desktop: small but powerful computer, usually found in the home or at school.

Laptop: portable computer, with a small screen and keyboard. Runs off a battery.

Palmtop: the smallest type of computer, it is hand held. A stylus, pen like device is used for input.

Tablet PC: this is a low specification laptop with no keyboard.

Hard Disk: contains a non-removable disk. It is stored inside the computer. It is used to store large
amounts of data. Data can be accessed very quickly.

Floppy Disk: Removable disc used to store small amounts of data. A floppy disk can be accessed
reasonably quickly. They are read using a floppy disk drive.

CD-ROM: very common backing storage media. It is read using a CD-ROM drive. It can store around
700Mb of data. This is a permanent medium that cannot be written to or erased.

CD-R (recordable): this is a type of CD that you can write data to, but only once. It is written using a CD
recordable drive.

Based on original notes by Mr J. Durkan, Hillpark Secondary School                                          12
CD-RW (re-writable): this is a type of CD that you can write to many times. Once it has been written on
once it can be erased and used again.

DVD-ROM: this is a very high capacity disk that is used to store a lot of data, around 4Gb. DVD’s work
the same way as CD’s but they store more data.

USB Stick (Pen or Flash Drive): this is a small pen like device that connects into a USB port on a
computer. It holds different amount of data depending on the size capacity of the stick. Data held on a
USB stick is accessed very quickly.

Laser – This is a quiet, fast, high quality printer, but tends to be expensive.
Inkjet – Also quiet and good quality and is cheaper than a Laser printer

Resolution: A printer’s quality depends on its resolution. It is measured in DPI (dots per inch). Higher
DPI means higher resolution and higher quality output.

Voice Recognition: a microphone is used to input the users speech into the computer system. Special
software is used to interpret what the user has said. This can be stored digitally on the machine.

Handwriting Recognition: this allows the user to write on a special surface and the computer software
will try and recognise the shapes being written and translate them into a digital form, that can then be
saved or changed on the computer.

Sound Card: this is a piece of hardware inside the CPU that enhances sound from the computer. A
multimedia computer must have a sound card.

Graphics Card: this is a piece of hardware inside the CPU that enhances graphics. It makes pictures;
computer games etc look better especially if a good monitor is used. A multimedia computer must have
a graphics card.

LCD (Liquid Crystal Display): Used on the monitors of modern computers and laptops. They make
laptop screens slimmer and lighter. They don’t require as much power as previous systems meaning that
laptop batteries will last longer

TFT (Thin Film Transistor): Used in LCD screens to produce clearer, brighter images

                                       Commercial Data Processing

Volume of Documents: large amounts of information can be managed and processed.

Speed of Processing: computers are ideal for accurate processing of data at high speed; it would take
much longer for data to be processed manually.

Repetitive Tasks: when humans do the same task again and again they get tired and make mistakes.
Computers can work constantly without making mistakes.

Speed of Access: data that is stored on computer can be accessed very quickly.

Managing Information: computers are used to store information, managers use this information to help
run their businesses.

Mainframe Computer: Large, expensive and powerful computer that is needed to manipulate the large
volumes of data generated by commercial systems.

Based on original notes by Mr J. Durkan, Hillpark Secondary School                                        13
Terminals: Keyboards and screens, not normally with any processing power of their own, which are
connected to the mainframe for users to access the system

Data & Information: data is the characters, numbers and symbols that are accepted, stored and
processed by the computer. Information is data that has a meaning and is understood by humans.

Data Processing Cycle: this is collecting, processing and sending data. It is broken down into 4 stages:
Data Collection & Preparation; Data Input; Data Processing & Storage and Data Output.

Data Collection & Preparation: this is the first stage in the cycle. This is where data is collected and
made ready to be input. Source documents are used to allow companies to easily collect information.

Data Input: this is the second stage where data is input into the computer and checked for accuracy.
Many different methods are used to collect data and check the accuracy.

Bar Codes: this is a series of black and white lines that make up a pattern. A bar code holds information
on a product such as product type, country it was made, etc, but not the price of the item. A bar code
scanner is used to input the information.

Magnetic Stripes: this is a band of magnetic material that is used to store details. They are usually found
on credit/debit cards.

MICR: Magnetic Ink Character Recognition. This is characters that appear on cheques. They are coated
in magnetic ink so they can be easily input into a computer. Humans can read these characters as they
are written in English. They make cheques more secure, because the magnetised characters can’t be

OCR: Optical Character Recognition. An optical character reader, a type of scanning device, is able to
read hand written characters directly into the computer. Printed pages of text can be read directly into a
word processor with suitable OCR software

Smart Cards: these are the new type of credit cards. They have a small computer chip built into them.
This chip holds the card information. A Smart card is more secure than a credit card with a magnetic strip.

Data Validation: This is a method of checking that data is sensible. Data validation can be done in many
ways: range check; length check etc

Data Verification: this is a method of checking that data is accurate or has been entered correctly. The
most common method of verifying data is to enter it twice. The first entry is compared to the second and if
they match the data is accurate and it is accepted.

Check Digit: a check digit is often added to numerical data to check that data has been correctly entered.
A check digit is calculated using the numbers that are entered. It adds up all the digits and then takes the
last digit from the total and adds it on to the original data. When data has been input, the computer
performs the same check, if it calculates the same check digit then the data is passed and accepted.

Range Check: this is checking to see that data is in an acceptable range. If the answer is within range
the computer will accept it, even although it might not be right. If it is out with the range it will refuse the
data e.g. a user entering the month in numeric form must type a number between 1 and 12.

Length Check: this will check to see that the right amount of characters has been entered. It will accept
the data if the length check number is the same as the amount of characters entered. This does not mean
that the right characters have been entered.

Data Processing & Storage: this is when the data that has been collected is stored and processed on
the computer. It takes the input and changes it to become output. When storing and processing data
there are two good practises that should be followed: Data Backup and Updating Data.

Updating Data: as the data is processed new information is added and stored. To make sure this
information is correct data should be regularly checked and if wrong it should be changed and kept up to

Based on original notes by Mr J. Durkan, Hillpark Secondary School                                                 14
Backup: this is keeping another copy of data in case something happens to the original. The second
copy should be kept in a different location, if possible.

Interactive Processing: this is when data is input into a computer and processed fairly quickly. This type
of processing is done when a reaction to the input is required in a reasonable timescale, but not as
urgently as real time processing. Using a cash line machine is an example of interactive processing

Sequential Access: information is retrieved by moving from the start to the end of the data file in order.
Magnetic tape is the most common media for sequential access. It has an advantage that it is cheap,
however the main disadvantage is having to read through all the records until you get to the one you
require. Sequential access is time consuming and better used when data is only accessed occasionally.

Random (Direct) Access: data is written to storage wherever the processor decide to store it, there is no
certain order it has to be saved in. This data can be accessed in any order, without having to read
through any records that you do not want to access, you just go directly to the record you require. Hard
disk, floppy disks, CD’s and DVD’s are random access devices.

Multi User Database: this is a database that can have more than one user controlling it at the same time.
It appears only to have one person using it, even although there are many. A multi user database is used
on a network.

Data Output: this is the last stage in the Data Processing Cycle. In this stage the output is given back to
the user. Data can be output to the user in three ways: on screen, paper, or file.

To Screen: this is simply displaying the results on the screen so the computer operator can see them.

To Paper: this is creating a hard copy of the information (printing it), so it can be handed out to people.

To File: output can also be sent to a file for storage or for later processing.

Single Entry Multiple Use: data is entered into the computer once and it can be used many times. It
saves the operator having to re-enter the information.

Social Implications
    Programmer: they write and modify any programs that are used to process the data
    Systems Analyst: they decide on the software and hardware needed for the business
    Engineer: they maintain the computer systems and fix any problems with them
    Network Manager: they have overall responsibility for the network and maintaining it
    Computer Crime: this covers computer fraud or stealing information from a computer system or
        destroying data. It can be almost impossible to prevent and it can cost the business millions of

Technical Implications
    E-Commerce: this is business conducted over the Internet
    On-line Services: these are businesses that allow their customers to access them over the
       Internet. Two of the most popular on-line services are online banking and online shopping
    POS: Point Of Sale: this is a till or terminal in a shop where items are paid for
    EFT: Electronic Funds Transfer. This is the transfer of money from one person/business to
       another. No cash is exchanged, instead a credit/debit card is used. Funds are then directly
       transferred from one person’s bank account to the others, with the POS being directly connected
       to the banks computer.

Economic Implications
    Initial Costs: this is the cost of buying the hardware and software. Furniture is also required for
      the new systems and possibly even a new office/location
    Running costs: these are the costs that have to be paid out constantly, after the business has
      been set up. They include consumables (ink, paper, discs); staff costs in wages; building rent;
      new computer parts; software updates

Based on original notes by Mr J. Durkan, Hillpark Secondary School                                            15
Security & Privacy
    Accuracy: the accuracy if information is very important. For businesses to run efficiently and
       effectively, they must ensure they store and process only accurate information
    Privacy: businesses must take security measures to make sure that no one is gaining access to
       information they are not allowed to see
    Security: businesses take two types of security precautions to stop anyone accessing
       information that they are not authorised to access. Physical Security i.e. restricting access to
       rooms where computers can be accessed and Software Security having employees use a log-
       on and password; having a firewall to stop hackers; encrypting data if it is sent across a network.
    Sale of Lists: some businesses have large lists of customer details that other companies would
       like. Some of the businesses with large lists may choose to sell this data to other companies.

                                         Some Useful Websites

Revise Computing (games, quizzes, revision notes):

BBC Standard Grade Bitesize Revision:

Based on original notes by Mr J. Durkan, Hillpark Secondary School                                      16

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