Genral theory notes
Quiz yourself by thinking what should be in
each of the black spaces below before clicking
on it to display the answer.
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| Hardware | Is any physical part of a computer (it is a group machine)
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| Hardware is made up of: | a)The CPU and Main Memory
b)Input Devices
c)Output Devices
d)Storage Devices
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| Main Memory: | Stores Programmes and Data for processing
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| CPU: | Central Processing Unit
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| Input Device: | These Devices read incoming data and pass it on to the CPU.
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| Examples are: | keyboard, Disk Drive, Scanner, Barcode reader, Voice Recognition, and Digital Camera.
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| Output Devices: | These Accept information from the CPU and display the results for the user. Examples are: Printer, Monitor
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| Storage Devices: | These keep information and instructions in the computer so Drive. that they can be used again. Examples are: CD’s, Floppy Disks, Hard
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| Mouse: | Used to select text, insert text or an icon on a page by clicking and dragging. The cursor changes shape depending on the task. E.g. Arrow, beam, egg timer shapes.
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| keyboard: | Used to type words on the page. The common type is a QWERTY keyboard; it is laid out in an ‘unfriendly’ manner, in order to slow down speed typists. The most commonly used letters are spaced out to avoid them sticking.
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| Bar code Reader: | They read or scan the zebra like bars that you see on most products The black and white bars are different widths and together they form a code called UPC or Universal Product Code.
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| Reader or Scanner: | They are used in upermarkets where the bar code on the item is scanned ajnd the products information is read, e.g its price.
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| Point of sale Terminal: | They are used to collect information on a product by scanning the bar code. e.g. its price, country of origin, and they record sale and produce a slip/receipt for the customer.
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| Digitiser: | Used for a drawing illustrations or creating graphics/pictures on a page.
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| Camera/Tape Recorder: | Used to input voice or visual pictures on to your computer.
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| VDE/Voice Data Entry: | It can accept human speech and convert it to the spoken word onto your screen.
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| OCR/Optical Character Reader (optical scanner): | They are devices that scan the document and turn it into readable form on your screen. It can be text, graphics, or photo material.
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| MICR/Magnetic Ink Character Reader: | They are used when documents, contain magnetic digits that contain information E.g. flat numbers on the bottom of the bank cheque that represents information about a customer’s account.
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| OMR/Optical Mark Recognition/reader: | The computer will pick up marks, e.g. pencil marks on sheet to collect information. E.g. Pencil marks on a score sheet.
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| Touch Screen: | It is a special screen which allows you to carry out a task by touching on the screen. E.g. a Point of Information (POI) screen in a shopping centre, you can touch it to find out information about different levels/floors.
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| Light Pen or Stylus: | You can use a special pen to touch the ‘touch screen’. It can be used to be highlight and select items. You can also make hand written entries.
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| Monitor/VDU or visual display unit: | This is the screen that you look at; it contains a soft copy of your information. As you key in text, it appears on the monitor for you to see.
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| Flat Scrreen Technology's : | Portable computers likie laptops, notebooks, and PDA's or personal digital assitants can have high resolution screens. The most common is the LCD or liquid Crystal Dislplay.
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| printer: | They are used to produce a copy of your information
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| Non-Impact printer: | These printers cannot make carbon coipies.
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| Plotter: | They are printing devices that produces a high quality image for drawings.
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| audio response: | Used to provide verbal respones using a voice simulator of pre-recored messages, e.g. Directory assistance.
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| Microfiche/film: | when large amounts of information need to be stored, miniature copiers of documents are kept on microfilm. Eg. Newspapers for the past 100 years.
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| Speaker: | Sends out Audio/Sound
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| Digital Projector: | Displays the Monitors Image on a Large Screen/Wall
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| Impact printer: | They are slower, noiser and ofthen breakdown, they are more inexpensive.
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| Plotter: | They are printing devices that produce a high quality image for drawings.
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| Audio response: | Use to provide verbal responses using a voice simulator or pre-recorded messages, e.g. Directory assistance.
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| Microfiche/film: | When large amount of information need to be stored, miniature copies of documents are kept on microfilm. E.g. Newspapers for the past 100 years.
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| Speaker | Sends out Audio/sound
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| Displays the Monitors | Displays the Monitors Image on Large Screen/Wall
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| STORAGE DEVICES | STORAGE DEVICES
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| Storage | It is very important to store your information carefully so that you do not lose it and know where to find it. You may store information directly onto your computer or on different types of storage devices e.g. Floppy Disk, CD or USB Key. It is important
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| Magnetic Disks and Disks Drives | This is often called a disk; information is stored in rings, called tracks.
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| Floppy Disk | It stores programmes and files, e.g. 3 1/2 Floppy that is called the A drive. Inside is a thin disk and has plastic case around it. It contains information in rings called tracks. Disks often have to be formatted, this means erasing all of it information
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| Disk Cartridge | It can store more information than a floppy disk, buts it is not portable.
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| Tape Drive | Still used in certain workplaces to store large amounts of information, but disks are faster and can store more information.
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| CDROM (optical) | It is a sliver plate, used to play audio and store information. They can store the same amount of information as 100 floppy disks. E.g. the Entire phone directory of the USA is contained on one CD ROM
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| WORM CD'S (optical) | Write once, Read Many times. They store large amounts of information, you can copy information to it once, you cannot change this information, but you can read/use it whenever you like.
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| ERASABLE CD'S: (optical) | You can copy information to it many times, and read information whenever you like.
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| USB Key | often called a pen drive/flash drive/memory stick or USB stick. It is inserted into the USB on your computer and information can be stored on it as a back up. It is portable.
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| Hard Disk | This is the permanent disk inside the tower of your computer that you can store information to, called the C Drive. It is not portable
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| MEMORY | MEMORY
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| Memory | This is the space the computer has to store information.
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| Byte | This is a letter or a symbol. A kilobyte (K) is 1024 Bytes. A Mega byte (MB) is 1 million Bytes. A Gigabyte (GB) is 1 Billion bytes.
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| Speed | The speed of this memory is measured in nanoseconds or billionths of a second. We use the symbol MHz or megahertz when described speed.
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| MIPS | Millions of Instructions per second, or the speed and memory size together.
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| Volatile/Non- Volatile | The main memory is volatile, that means if the computer is switched off, it will be lost. So information should always be stored on a disk, or a hard drive, so that it is safe and non volatile
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| RAM/ random access memory | This memory stored programmes and it stores information or small commands while you are working. It is volatile. E.g. if you are typing and you decide to cut and paste. You may right click, and cut, go to another spot on the page and paste; the computer b
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| ROM/ Read only memory | These are permanent instructions in the computer. When you turn off the computer it will still know what to do and how to do it when you turn it on. For Example: when you turn on a computer it knows to check is the printer connected it knows " enter" key
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| Storage Capacity | This is the amount of information that a computer can hold.
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| Backup | This means to create another safe copy in case one gets destroyed, by a virus (bug on a file)
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| SOFTWARE | Before a computer or any hardware can actually read data, process/ change it and produce information for you , it needs a set of instructions. These instructions are in the software.
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| Types | So the soft ware is like "set of instructions" put together that helps the computer carry out different jobs. There are 2 main types of software. They are: Operating systems software and Applications/Programmes software.
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| Operating Systems software or OS | This is the software supervises the over all operation's od a computer Examples are; IBM use DOS or DISK operating Software and apple, Macintosh, Dell and gateway use windows operating software. Windows is what you are using and you can carry out a job by
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| Compatible /Incompatible Disks | A disk is prepared for one OS may not work on another OS. For Examples Word perfect for windows may not work in Macintosh, you may have to get the Macintosh version. In this case they are incompatible or they cannot be used together.
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| Application's Software | These are programmes that you can simply buy off the shelf form a retailer/ shop like PC World. In some cases a company may want to use specific Programmes, in that case they cam get the programme. specially designed; E.g. schools use a facilty programme
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| Networks, connectivity & communications | This is an idea that computer resources in an area can be shared .
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| Information such as files can be shared | A large computer called a server is used to help share files and information on the network for many people to use
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| Two Types of networks | LAN and WAN
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| WAN | This network is used to transfer and share information over a great distance e.g. One country to another country (Wide Area Network)
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| LAN | A local area network is used to transfer and share information and resources when computers are close to one another. E.g. The network may connect devices within in a room or a building .
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| Internet | allows you to connect with 1000's of networks worldwide.
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| ISP | Internet service provider
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| ISDN | Line or integrated systems digtal network
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| HTTP | HYper text transfer protocol
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| HTML | Hyper text mark up language
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| search engine | Google or Yahoo
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| Video Compression | allows full motion video and sound to be transmitted over the telephone lines
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| Ergonomics | This refers to any health and safety issues relating to PC use
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To hide a column, click on the column name.
To hide the entire table, click on the "Hide All" button.
You may also shuffle the rows of the table by clicking on the "Shuffle" button.
Or sort by any of the columns using the down arrow next to any column heading.
If you know all the data on any row, you can temporarily remove it by tapping the trash can to the right of the row.
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