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1. Computers, data and information
A computer is an information processing machine. Computers process data to
produce information. The sets of instructions that humans give computers are
called programs or software. Software that carries out a particular type of task for a
user is often called applications software.

Reasons for…

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Computer Systems
Hardware is the name that is given to any part of a computer that you can actually
touch. An individual piece of hardware is called a device. The basic hardware of any
computer consists of a central processing unit (CPU) along with input, output and
backing storage devices.…

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Keyboard
The keyboard is the most common type
of input device. Ordinary computer
keyboards have their keys arranged in a
similar way to those on a typewriter.
This way of arranging the keys is called
QWERTY because of the order that
they keys appear in on the first row of…

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Graphics Tablet
A graphics table consists of a flat surface and a pen, or
stylus, which can be used to produce freehand drawings
or trace around shapes. When the special pen touches
the surface of the graphics tablet data about its position
is sent to the computer. This data is…

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Bar codes
A bar code is a set of lines of different thicknesses that represent a number. Bar
Code Readers are used to input data from bar codes. Most products in shops have
bar codes on them. Bar code readers work by shining a beam of light on the lines…

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ask for the same data to be entered twice. If both entries do not match up the data
is rejected.

Validation
Validation checks are carried out by software to make sure that data which has been
entered is allowable and sensible. Data that is not sensible or allowed is rejected…

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Hash total
Hash totals are used to check that groups of numbers have been input correctly.
A hash total is the sum of a group of numbers that are going to be input. The hash
total is input along with the numbers. The computer calculates a hash total for the…

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Advantages of coding values:
Fewer key presses are needed when entering a value in the field so there is less
chance of the wrong keys being pressed
Time is saved when entering data because there is less to type in each time
Database packages allow automatic validation checks to be…

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computer is switched off. Memory which is not wiped clean when the computer is
turned off is called non-volatile memory.

PROM and EPROM
PROM and EPROM are both special types of programmable read only memory.
PROM stands for Programmable Read Only Memory. This type of memory can be
programmed once…

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Magneto-Optical disks which can have data written to them any number of
times just like a hard disk.

Digital versatile disk (DVD)
DVD is the latest way of storing data. DVD discs are expected to replace ordinary
compact discs and video tapes in the future. A DVD disc can store…

Comments

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yourboykyle

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