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I.C.T

General Theory Notes

HARDWARE
Hardware is any physical part of a computer(it is a group of machines)
Hardware is made up of: (a) The CPU and Main Memory (b) Input Devices (c) Output Devices (d) Storage Devices
Main Memory: Stored Programmes and Date for processing.
CPU: Central Processing Unit
Input Devices: : 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.
Output Devices: these Accept information from the CPU and display the results for the user. Examples are: Printer, Monitor.
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.
Mouse: Used to select text,insert text or an icon on a page by clicking and dragging. E.G. Arrow
Keyboard: Used to type words on the page. The most common type is a QWERTY keyboard.
Bar Code Reader: They read or scan the zebra like bars that you see on most products.
Wand Reader: . The wand reader is a hand held type that can be used for scanning items e.g. a Library book.
Scanner: This scanner is often connected to a POS or point of sale terminal called an electronic cash register.
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.
Digitiser: Used for drawing illustrations or creating graphics/pictures on a page.
Camera/Tape Recorder: Used to input voice or visual pictures on to your computer.
VDE-Voice Data Entry: It can accept human speech and convert it to the spoken word onto your screen.
ORC-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. The results can be cut, copied and pasted, then saved to a disk. E.G. Books
MIRC- Magnetic Ink Character Reader: They are used when documents, contain magnetic digits that contain information. E.G Flat numbers on the bottom of a bank cheque that represents information about a customer's account.
OMR- Optical Mark Recoginition/Reader: The computer will pick up marks, e.g. pencil marks on a sheet to collect information. E.G. Pencil marks on a score sheet.
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.
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.
Monitor- VDU- Visual Display Unit: This is the screen that you look at it; it contains a soft copy of your information. As you key in text, it appears on the Monitor for you to see. There are different types of monitors; one is the CRT or Cathode Ray Tube.
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 or Liquid Crystal Display.
Printer: They are used to produce a hard copy of your infoirmation. There are many types; the two main types are impact and Non Impact.
Non-Impact Printer: These printers cannot make carbon copies. Examples are: Thermal Printer, Ink Jet Printer, Laser Printer.
Imapct Printer: They are slower ,noisier and often breakdown, they are more inexpensive. Examples are: A Dot Matrix and Character Printer.
Plotter: They are printing devices that produce a high quality image of drawings.
Audio Response: Used to provide verbal responses using a voice simulator or pre-recorded messages, E.G. Directory assistance.
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 100 years
Speaker: Sends out Audio/Sound.
Digital Projector: Displays the Monitors Image on a Large Screen/Wall.
STORAGE DEVICES: - 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 to store back up's also, in case one copy becomes unusable. (a back up is like a second copy of your information).
Magnetic Disk and Disk Drives: This is often called a disk; information is stored in rings, called tracks.
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 in order to make it work. This can be done by right clicking on the disk icon and clicking format.
Disk cartridge: It can store more information than a floppy disk, but it is not portable.
Tape Drive: Still used in certain workplaces to store large amounts of information, but disks are faster and can store more information.
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 one one CD ROM.
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.
ERASABLE CD'S (Optical): You can copy information to it many times, and read information whenever you like.
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.
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.
MEMORY: - Memory: This is the space the computer has to store information.
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.
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.
MIPS: Millions of Instructions per second, or the speed and memory size together.
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.
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 may right click, and cut, go to another spot on the page and past; the computer 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.
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 how to check is the printer connected, it knows that the 'enter' key on a keyboard will skip a line. So it is like a computers long term memory, it won't ever forget how to do it.
Storage Capacity: This is the amount of information that a computer can hold.
Backup: This means to create another safe copy in case one gets destroyed, by a virus (bug on a file).
SOFTWARE: - 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.
Types: So the software is like a 'set of instructions' put together that helps the computer carry out different jobs. These are 2 main types of Software. They are: Operating Systems Software and Applications/Programme Software.
Operating Systems Software or OS: This software supervises the overall operations of a computer. Examples are: IBM use DOS or Disk Operating Software, and Apple, Macintosh, Dell, and Gateway us Windows Operating Software.
Windows is what you are using and you can carry out a job by clicking on a Graphic/Picture Symbol or an ICON by clicking on them. E.G. a Scissors will cut text.
Compatible/Incompatible Disks: A disk that is prepared for one OS may not work on another OS. For Example: 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. If you can use a disk in two different Operating Systems, then they are compatible.
Applications Software (Program Software): These are programs that you can simply buy off the shelf from a retailer/shop like PC world. In some cases a company may want to use specific programs, in that case they can get the programme specially designed;
E.g Schools uses a Facility Programme to keep school records, Accountants use a Payroll Programme to do their accounts.
Network: This is the idea that computer resources in an area can be shared: it is shared by an Integrated Computer System (integrated/interconnected). For Example: Your computer room in school may have 20 computers but only 1 printer,
if for example 10 of these computers can send documents to the 1 printer to print, then they are sharing the resource or sharing the 1 printer.
It makes more sense to share an expensive resource like a printer, rather than to have 1 printer attached to each computer.
Information such as files can also be shared: Information such as files can also be shared using a network. A large computer called a server is used to help share files and information on the network for many people to use.
There are two types of network: LAN and WAN
WAN: This network is used to transfer and share information over a great distance, for example, from one country to another country.