General Theory Notes
Quiz yourself by thinking what should be in
each of the black spaces below before clicking
on it to display the answer.
Help!
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| Hardware: | is any physical part of a computer (it is group of machines)
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| Hardware is made up of: | a) The CPU and the Main Memory
b) Inputs Devices
c) Outputs Devices
d) Storage Devices
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| Main memory: | stores programmes and Data for processing
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| CPU: | centarl processes unit (its the brain of the computer)
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| input Device: | These devices read incoming data and pass it on to the CPU. Example are: Keyboard ,Disk Drive, Scanner, Bar Code 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. Example are: Printer, Monitor
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| storages Devices: | these keep information and instructions in the computer so that they can be used again. Example are : CD’s, Floppy, Disks, Hard Drive.
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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 most common type is a QWERTY keyboard; it is laid out in an ‘unfriendly’ manner, in order to slow down speed typists.
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| bar code reade/wand reader scanner | They read or scan the zebra like bar that you see on most products. The black and white bars are different widths and together they from a code called a UPC or universal product code. They are used in supermarkets where the bar cose on the item
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| point of sale terminal | They are used to collect information on a product by scanning the bar code. They record and store information e.g. its price, country of origin, and they record the sale and produce a slip/receipt for the customer
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| Digitiser; | They are used to collect information on a product by scanning the bar code. They record and store information e.g. its price, country of origin, and they record the sale and produce a slip/receipt for the customer
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| Camera/Tape recorder: | Used to inputs 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 onto readable form your screen. It can be text, graphics or photo material. The results can be cut, copied and pasted. Then saved to a disk.
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| MICR/Magnetic Ink character Reader: | They are used when document, contain magnetic digits that contain information. E.g. flat number on the bottom of a bank cheque
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| OMR/optical mark recognition/ reader: | The computer 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,
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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 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 highlight and select items. You can also make hand written entries
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| monitor/VDU or visual display unit | the is the screen that you look at: it contains a soft copy of your information .(the copy of your work on the computer
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| flat screen technology's | portable computer like laptops, notebooks, and PDA's or personal digital assistants can have high resolution screens. the most common is the LCD or liquid Crystal display
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| printer | they are used to produce a hard copy of your information. there are many types: the two main types are impact and Non impact . the speed at which pages print.
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| non-impact printer: | these printers cannot make carbon copies. example are: thermal printer: they respond to heat and creat letters on special papaer. they are slower than Ink-jet and paper is expensive.
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| impact printer | they are slower,noisier and ofen breakdown, they are more inexpensive. example are; A dot matrix: it creates characters from pins the pins strike against a carbon ribbon to print on paper.
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| plotter | they are printing devices that produce a high quality image for drawing.
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| audio response | used to provide verbal responses using a voice simulator or pre-recorded message, e.g. Directory assistance.
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| Microfiche/film | when large amount of information need to be stored, miniature copies od document are kept on assistance.
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| speaker | sends out Audio/Sound
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| digital projector | Display the Monitors image on a Large screen/wall
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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 finds 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 Disk Drives: | this is often called a disk: information is stored in rings, called tracks.
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| Floppy Disk | it stores programs and files, e.g. 3.5 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. Disk often have to be formatted, this means erasing all of its informationin or
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| Disk cartridge | it can store more information than a floppy disk, but it is not portable.
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| Tape Drive | still used in certain workplaces to store large amounts of information 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 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 pen drive/flash drive/memory stick or USB stick. It is inserted into USB on your computer and information can be stored on it as a back up. It is portable
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| Hard drive | 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 | 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 1022 Bytes. a Megabyte (Mb) is 1 million Bytes. A Gigabyte (Gb) is 1 billion bytes
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| speed | The speed od this memory is measured in nanoseconds or billionths of a second. We use the symbol MHz or megahertz when describing 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 the hard drive, so that it is safe and non volatile.
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| Ram/random access memory | This memory store 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 kn
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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 that the 'en
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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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