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.
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| Hardware | is any physical part of a computer (it is a group of machines)
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| 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: | Controls all operations/jobs, it reads all data into the main memory from an input Device; it processes the data, changes it and produces information for you to ues). It is like the brain of the computer.
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| Input Device: | : These Devices read incoming Data and pass it on to the CPU. Examples 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. Examples are: Printer Monitor.
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| Storage Devices: | these keep information and instructions in the Computer so that they can be used again. Examples are: CD`s, Floppy Disks, Hard Drive.
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| Mouse: | Used select text, insert text or an icon on a page by clicking and dragging. The cursor changes shape depending on the task
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| Keyboard: | Used to type words on 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 Reader/wand Reader or scanner: | 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 from a code called a UPC or Universal product code.
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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
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| Digitiser: | Used for drawing illustrations or creating graphics/pictures on 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 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.
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| MICR/Magnetic Ink Character Reader: | They are used when documents, contain magnetic digits that contain information.
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| OMR/Optical Mark Recognition/Reader: | The computer will pick up marks, 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.
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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 ans 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.
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| flat screen technology`s | portable computers like laptops,notebooks,and PDA`s or personal digital assistants can have high resolution screens. the most common is the LCD 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.
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| Non-Impact Printer | these printers canot make carbon copies.
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| impact printer | they are slower,noisier and often breakdown theyare 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: | used to provide verbal
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| Microfiche/film: | when large amounts of information need to be stored, miniature copies of documents are kept on microfilm. E.g. Newspapers for the past 100years.
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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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| 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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| to store back up's also; in case one copy becomes unusable.(a back up is like a second copy of your information).
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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 1/2 Floppy that is called the A drive. inside is a thin disk and has a plastic case around it. it contains information in rings called tracks. Disks often have to be formatted, this means erasing all of its information
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| in order to make it work. this can be done by right clicking on the disk icon and clicking on format.
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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, but disks are faster and can store more information.
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| CDROM: (Optical) | it is a silver 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 UBS 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: | 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 Megabyte ( 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 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 stores 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 many right click and cut go to another spot on the page and paste; the computer
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| knows to do this as it has stored it in its memory. But if you switched off the computer before you clicked paste, it would not remember to paste this text when you switch it back on. it's like a short term memory.
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| ROM/READ only Memory: | these are permanent instructions in the computer. when you turn off the computer it will 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 it the printer connected, it knows that the enter
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| key on keyboard will skip a line. so it is like a computers long term memory, it wont ever forget how to do it.
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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 instruction are in the Software.
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| types: | so the software is like a set
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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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