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TSR Wiki > Study Help > Subjects and Revision > Revision Notes > ICT > Complete GCSE ICT Note for AQA Exam Board

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Contents 1 Data 2 Computer systems v Manual systems 3 Types of computer 4 Networks-LANS AND WANS 5 'Networks-security 6 Input devices 7 The CPU 8 Output devices-PRINTERS 9 Data storage-ROM and RAM 10 Backing storage 11 Operating systems 12 User interfaces 13 Data capture 14 Data validation and verification 15 Data processing 16 Access to data 17 Implementation and evaluation 18 INTERNET 19 Health and safety 20 Comments

Data

• Bit- each individual ‘1’ or ‘0’ is a bit-short for binary digit.
• Byte- 8 bits are a byte.
• Kilobyte-is 1000 bytes (1024)
• Megabyte-is 1,000,000 bytes
• Gigabyte-is 1,000,000,000 bytes
• Each character on keyboard-8 bit

Computer systems v Manual systems

• Benefits of computer system:
• Takes up less space
• Searching is very quick
• More than one person can access the same data form their network PC.
• The data stays in the computers memory
• Fewer staff are needed to look after a computer system
• Reports can be generated very quickly-automated

• Problems of a computer system:
• Setting up is very expensive
• Computer systems need people to maintain them
• POWER CUTS!
• It is easy to hack into a computer system.

Types of computer

• Mainframes-biggest
• They are the most powerful
• They are very large
• VERY expensive
• They are used in BIG businesses-banks, insurance companies.

• Minicomputers-middle
• Less powerful than mainframe but more powerful than micros

• Microcomputers-most common-usually called PC’s.
• Are designed to stand alone
• Much less powerful than mainframes.

Networks-LANS AND WANS

• Local area network-LAN-small-offices and schools.
• Wide area network-WAN-large-link together different places.

• Advantage of using networks-peripherals such as printers can be shared amongst several users.
• Software can be shared amongst several users.
• Communication across network is fast + cheap

• Disadvantage of using networks-cabling can be expensive to install and replace
• A fault with the server will prevent the whole network from working
• Security measures are needed to restrict access to network
• WANS are vulnerable to hackers and viruses.

'Networks-security

• SERIAL NUMBERS
• ALARMS
• DOORS
• FIRE PROTECTION
• LOCK
• AVOID
• BLINDS

• JUST REMEMBER SADFLAB

• Passwords-should be changed frequently.
• Backup-and files should be kept secure-in locked fireproof rooms.

Input devices

• Keyboards
• Mouses-touchpad, tracker balls.
• Graphics pads make drawing easier and more accurate.
• Joystick
• Scanner
• OCR scanners-read text
• MICR-magnetic ink character recognition-cheques
• OMR-optical mark recognition-registers-read lines in boxes.
• Credit cards have a magnetic stripe on the back-carries info so the computer can identify the customer.

The CPU

• The control unit makes the system work-CU
• It controls all hardware attached to the system.
• It controls the output and input of data
• It controls the flow of data within the CPU

• The ALU is where the processing happens-Arithmetic and logic unit.
• Arithmetic part-does calculations!
• Logic part-makes decisions like whether a number is bigger than –5.

• The IAS is where active data is stored.
• IAS-immediate access store

Output devices-PRINTERS

• Dot matrix
• Laser
• Inkjet

• Advantage of dot matrix-cheap and low operating costs.
• Disadvantage of dot matrix-low res, slow, noisy.

• Advantage of laser-high res, very fast
• Disadvantage of laser-expensive.

• Advantage of inkjet- good res, cheap
• Disadvantage of inkjet- slow (ish), expensive to run

Data storage-ROM and RAM

• RAM is temporary-random access memory
• It stores data as electric signals.
• If the power is cut or electricity fails everything in RAM-LOST!
• ROM is permanent-Read-only memory
• ROM however is not a backing storage on hard disk.

Backing storage

• Hard disk-main internal storage.
• Large capacity-range from 20gb to 100gb!
• Floppy disk-3.5 inch
• 1.44 mb-very small capacity
• Magnetic tape-used to backup large amounts of data-cheap as well!
• Access time is slow because it has to run through whole disc to find something.
• Optical disks have fast access time.
• CD-ROMS-oldest type-650mb
• CD-R’s-sold as blanks-data can be written only once to it.
• CD-RW’s-most popular. RW stands for read and write.
• DVD-17 gb
• ZIP disks-larger, thicker-100mb

Operating systems

1. Enable applications to run
2. Enables software to communicate with systems hardware
3. It manages system resources
4. Monitors performance of system
5. Prompts error messages.

• Multi tasking means an OS can run more than one program at a time
• Basic systems that are not multi tasking are called single program mode OS’s.

User interfaces

• Can be command driven-blank screen and commands and code used.
• Can be menu driven- headings and menus
• Most common is GUI-graphical user interface-combines menu driven and icons-
• GUI’s are known as WIMPS-windows, icons, menus, pointers

Data capture

• Data capture turns info into data
• Automatic data capture-is fast and accurate
• BUT manual data capture- is necessary sometimes, and it’s cheaper!

Data validation and verification

• Validation-4 checks
• Range check-checks data is in specified range
• Presence check-makes sure data is present
• Check digit-check that numerical data is accurate
• Data type-checks that text is not where numbers are meant to be.
• Verification-2 checks
• Proof reading-read it and make sure that its accurate
• Double-entry-data entered twice and compared

• Validation problems- mistakes may be allowed if carried out wrong and only makes sure that data is right type-NOT ACCURATE.

• Verification problems-double entry is time consuming-expensive and proof reading is time consuming and does not eliminate human error.

Data processing

• Real time processing does it instantly
• Batch processing-all in one go
• Transaction processing-one off specials
• Interactive processing-talk to the computer

Access to data

• Serial access-records are stored one after another in creation order
• Sequential access-records are stored one after another acc. to sensible order
• Direct access-can go to record directly

Implementation and evaluation

• 3 types of implementation-
• Direct-straight away and old system goes down but bugs not picked up in testing-bad news!
• Phased-different parts are introduced one at a time
• Old system is kept running

• Parallel-new system is introduced in one go BUT old system stays
• New system can be tested quickly but all tasks need to be done twice.
• Evaluation just checks that the system meets all objectives

• DTP SOFTWARE-is good because it creates pro. Looking documents and the layout can be changed more easily than word processors and the user can control the number of pages more easily than a word processor

INTERNET

• The Internet is basically a very big WAN.
• To connect you need a PC connected to a normal telephone line and a modem
• You use your modem to dial up a computer that is owned by an ISP
• You need 2 pieces of software- email client and web browser.
• Internet has 2 main parts-WWW (world wide web) and email.
• Speed of access depends on 3 things-
• Modem speed-either 28kbps or 56kbps
• Telephone line-either ISDN or ADSL
• Volume of traffic-more people using the Internet, the slower the speed of access.

• Http-hypertext transfers protocol-language that web uses.

• http://www. Cgpbooks.co.uk

• Cgpbooks-domain name

Health and safety

• RSI- repetitive strain injury-aches pains and muscle or tendon damage

Spending too long in front of a VDU can cause eyestrain and headaches. Circulation and fitness and back problems result from sitting all day in front of a computer

• Solutions-
  • Take regular breaks, look away from screen walk around and exercise fingers
  • Use correct equipment- a chair with a backrest, a keyboard making it easier to type without straining
  • Good background lighting, good screens and a screen filter to reduce VDU glare.

Comments

Hi, i hope these help you with revision. they did a fantastic job in my class, because with just a few exceptions every single boy in my class got an a/a*. if you are on the AQA board, and are doing ICT, learn these notes and i can really guarantee that you'll pass. make sure you read it a few times til it sticks in your head!!!

good luck..