Specification
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Explanation
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The Processor -
also known as the Microprocessor
or the Central processing Unit (CPU).
See Lesson 3 for further information
on the Inside of the Computer. |
Two companies - Intel Inc. and AMD
Inc. - manufacture most of today's PC processors and both offer
a range that balances price and performance. Processors are generally
defined by their speed - in megahertz or MHz - and this relates
to the number of operations they can perform per second. The
higher the megahertz value, the faster the PC will perform and
the more expensive it will be.
Unlike IBM-compatible PCs (which use Intel or AMD processors),
Apple computers use PowerPC processors. These processors were
jointly developed by Motorola, IBM and Apple and first made an
appearance in 1994 when they were used in Apple's Power Mac range
of computers.
As a general rule, the speed of a PowerPC processor (in megahertz)
should not be compared directly with the speed of an Intel/AMD
processor - a 500MHz PowerPC processor will compare favourably
with a 700/800MHz Intel/AMD processor - as they are based on
different microprocessor technologies. |
RAM
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Random Access Memory. The
main working memory in a computer is called random access memory
or RAM. The processor uses this memory to run programs. this type
of memory stores programs and data only while you are working
on it. When you stop working on the data you must save
it or it will be lost when you shut down the computer. RAM is measured
in megabytes (MB). It comes in 32-bit, 64-bit, 128-bit, 256-bit,
and higher, and you can add additional "blocks" of RAM,
depending on your computer. A minimum of 128MB of RAM is recommended
for general purpose computers. 256MB of RAM is recommended for
PCs running multimedia applications, i.e., those on which digital
music, digital video or high-end graphics are being created/edited. |
ROM
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Read Only Memory Built-in computer
memory that can be read but not written to. ROM contains the programming
that allows your computer to boot up each time you turn it on,
and it contains essential system programs that neither you or the
computer can erase. Unlike a computer's random access memory (RAM),
ROM does not lose its data when the computer power is turned off.
It is sustained by a small, long-life battery. (If you ever run
the hardware setup procedure on your computer, you are in effect
writing to ROM.) |
Bits and Bytes
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A bit is the basic
unit of information in a binary numbering system, it takes 8
bits to make up a byte.
8
bits = 1 byte
For the most part, bits are used to describe transmission
speeds, whereas bytes generally refer to storage capacity.
It works like this: The electronic
circuitry in computers detects the difference between two states (high
current and low current) and represents these two states as one of two
numbers, 1 or 0. These basic high/low, either/or, yes/no units of information
are called bits. The word bit derives from the phrase "binary digit."
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Storage - The Hard Drive
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The hard drive is the computer's
primary storage area. It stores the applications and programs
that run on the PC, as well as any work created by users. From
a school's perspective, the capacity of the hard drive, something
that is measured in gigabytes (GB), is a key criterion and should
be given due consideration when reviewing PC specifications.A
hard drive capacity of at least 20GB is recommended for general
purpose PCs. A hard drive capacity of 40GB or more is recommended
if working with multimedia applications where large graphics
and digital audio/video files are being created and stored.
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Monitors
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Monitor
specifications are described in terms of screen size and quality.
The screen size is measured in inches
and this number refers to the diagonal length from one corner of
the monitor box to the other. Be aware that a stated screen size
of 17" will normally result in a viewable, or useable, area
of only 15.1". Monitor quality is measured in dot pitch or
strip pitch. The lower the number of pitch, the sharper the images.
A measurement of .27mm is average for dot pitch.
Average computers usually come with a 17" monitor and
this is adequate for most general purpose applications. Larger
19" or 21" monitors are available and may be appropriate
if video editing and advanced graphics work is being carried
out.
Teachers of students with special needs may want to consider
using larger monitors with their students.
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CD-ROM and DVD-ROM Drives
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CD-ROM drives are standard on PCs and
allow the information on a compact disc (either data or audio)
to be read by the PC. It is defined by its speed (i.e., 16x or
16 speed, 48x or 48 speed). DVD-ROM drives can read both CDs and
DVDs. Educational software is being developed in both DVD and CD
formats, but a DVD can hold over 25 times more data than a CD. |
Graphics and Sound Card
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These cards are installed inside
a PC and are responsible for determining the quality of the audio
and visuals (graphics and video) output by the computer. They
hold their own memory (in MB), which is why they add to a computer's
capability.
A graphics card with 16 or 32MB of memory
is recommended for general purpose PCs. Computers running high-end
applications may require a 64MB graphics card.
A sound card generally comes as standard
in most PCs purchased today. If students intend to work extensively
with digital music, the school should consider getting a high-end
sound card as this will create greater depth, complexity and
realism of sound.
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Speakers and Headphones
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Most computers come with either built-in
or external speakers. Schools may also consider buying headphones
to control sound levels within a classroom or computer room. Cheap
'headphone splitters' can also be purchased - these enable two
sets of headphones to be used per computer. |
Network Interface Card
(NIC)
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If the computer is to become part of
a school network, either when purchased or at some point in the
future, it is recommended that a suitable network interface card
be included in the spec. A network card allows a computer to be
connected to a network. On newer computer networks, a 10/100 switch
network interface card will suffice. Some PCs are manufactured
with a built-in network card as standard. If this is the case,
check that it is compatible with either the existing or planned
school network. |
Modems
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A modem allows a computer to connect
to the Internet via a standard telephone line. Most PC manufacturers
include modems as standard in all new machines.
PCs being purchased for use within a networked environment
do not require modems (though they may arrive with them anyway).
Most modern modems will operate as fax machines as well allowing users
talk over the Internet. These are termed 'data/fax/voice' modems.
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Operating
System
See Lesson 2 for more information
on the Operating System.
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PCs are shipped with an operating system
pre-installed. It is worth checking that your existing software
will still work with the operating system of any new systems being
purchased. It may be possible to choose a particular operating
system and, if so, this may help standardise new machines with
existing school PCs. |
Computers are shipped with an operating
system pre-installed. It is worth checking that your existing software
will still work with the operating system (OS) of any new systems
being purchased. It may be possible to choose a particular operating
system and, if so, this may help standardise new machines with
existing school computers. Mac OS 9 and the UNIX-based Mac OS X
presently come pre-installed on iMacs. |