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Storing Data
Data storage devices can be divided into 2 main
categories:
Backing storage is used to store programs and data
when they are not being used or when a computer
is switched off.
When programs and data are needed they are
copied into main memory but also still remain on
backing storage.
Magnetic tape drives, floppy disk drives and hard
disk drives are all examples of backing storage
devices.
The Main Memory contains two types of memory
chip called ROM and RAM which hold program
instructions and data.…read more

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BITS and BYTES
Computers store and process data using
binary numbers.
A single unit in binary is called a bit which
stands for binary digit.
Computer memory is measured in bytes.
One byte is made up of eight bits.
One byte can store one character.
1 0 0 0 0 0 1 0
The eight bit binary code in this byte
represents the letter A…read more

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Computer Memory
The size of a computer's memory is normally
measured in kilobytes (Kb), megabytes
(Mb) or gigabytes (Gb). The table below
shows some of the main units of size that we
use to measure computer memory.
Measurement Size (bytes) Symbol
kilobyte 1,024 Kb
megabyte 1,048,576 Mb
gigabyte 1,073,741,824 Gb…read more

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Random Access Memory
(RAM)
RAM is the computer's `working memory'.
RAM temporarily stores programs and data
that are being used at a given time.
The contents of RAM can be changed and
are lost when the computer is turned off.
Memory which is wiped clean when the
computer is turned off is called volatile
memory.…read more

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Read Only Memory (ROM)
The main use of ROM memory chips in a
computer is to store the program that runs
when the computer is turned on which loads
the operating system (e.g. Windows 2000)
from disk.
The contents of ROM can't be changed and
aren't lost when the computer is switched off.
Memory which isn't wiped clean when the
computer is turned off is called non-volatile
memory.…read more

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