AS Computing Revision

awsome notes made by my friend ross =)

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By Ross Evans & Nicholas Wills
Computing Revision
Input Device ­ A device that allows the user to enter data into the system. E.g. Mouse /
keyboard
Output Device ­ A device that presents data to the user. E.g. Monitor / speakers
Storage Device ­ A device that keeps data that has been collected for future use. E.g. Hard
Drive
Hardware ­ The physical components of the computer.
Software ­ Allows the hardware to work and it contains a set of programs to let the user do
something useful.
Peripheral Device ­ External to the computer. Attached to the computer.
Systems Software ­ Programs that control the operation of a computer system.
Applications Software ­ Programs that allow the user to do something useful / tasks.
ROM ­ Non-volatile, permanent, cannot be changed, Smaller than RAM. Contains the boot
program.
RAM ­ Volatile, used for running application, deleted after the computer is turned off. Allows
changes to be made to saved documents. Contains application software.
LAN ­ Local Area Network. Computers linked together over a small area. Allows communication
to take place wirelessly or hardwired.
WAN ­ Wide Area Network. Used over geographical locations. More subject to interception
than LAN.
Parity Check ­ Odd or even parity check. Before the data is sent, the parity is determined as
either odd or even. When it is odd, the number of 1s adds up to an odd number and the number of 0s
are odd. When even, the number of 1s add up to an even number and the number of 0s are even.
Echo Check ­ The data is transmitted and received by the other device. The other device then
retransmits the data. The data is compared with the original and if the data is the same, then the data
isn't being intercepted or corrupted along the way. If it does happen then the data will be retransmitted
for a second time and checked again.
Check Sum ­ A hash algorithm is performed. A digit is attached to the file. When the file arrives
the other machine knows what has been performed. It will perform the calculation and compare the digit
if they are the same then the data is correct.
Operating System ­ A set of programs designed to manage the hardware of the system.
Single User Operating System ­ Allow one user at a time to use the system, allocates each user
with rights. Keeps the user files separate.
Multi Tasking Operating System ­ Allows more than one task / software to run simultaneously,
use of separate windows for each task. Each is given an amount of processor time before going onto
the next. E.g. Plays music while typing essay.
UTILITIES:
Utility ­ A software program used for low level system maintenance, it often comes as part of
the OS.
Back-up utility ­ Schedules backup process with specified files.
File Compression Utility ­ Makes file smaller for archiving or transfer
Check Disk (Scan Disk) Utility ­ Checks the disk for physical or logical errors. E.g. hard drive
Driver Software Utility ­ Software that allows hardware to be used with the OS.

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By Ross Evans & Nicholas Wills
Anti-virus Utility­ Checks for viruses and removes them
Packet Switching ­ Packets (labelled / destination) are sent following the most convenient
path, this means packets may use different routes. When a packet reaches a machine along a network
the label is read. If that machine is not the destination, the packet is launched along the most suitable
route.
Circuit Switching ­ The packets follow one established route and that route is held for the
duration of the data transfer.…read more

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By Ross Evans & Nicholas Wills
OMR ­ Optical Mark recognition, the process of capturing human marked data from documents
or forms such as surveys and tests.
OCR ­ Is the electronic translation of scanned images of handwritten, typewritten or printed
text into machine ­ encoded text; to be edited or sent.
MICR ­ Magnetic Ink Character Recognition, A character recognition technology used primarily
by the booking industry to facilitate the processing of cheques.…read more

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By Ross Evans & Nicholas Wills
T ­ Technical Feasibility, Is the proposed system possible? Does the technology exist to make
it?
E ­ Economical Feasibility, Is the proposed system within the budget? How much will it cost?
L ­ Legal Feasibility, Is the proposed system within the law?
O ­ Operational Feasibility, Does the proposed system do what it's supposed to do? Does it
work?
S ­ Schedule Feasibility, How long will the system take to build?
Items in the User Documentation ­ FAQ,…read more

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