S2 Computer Literacy
Overview of Computer Hardware
It is the main circuit board that links all
the hardware components together.
There are many chips or IC (Integrated
Circuit) on the motherboard which
contains millions of transistors.
CPU (Central Processing Unit)
It interprets and performs instructions
of a computer program.
The most determining factor in how
powerful a computer is.
A CPU in a common PC system is
known as the microprocessor.
A model of Computer
A CPU consists of two parts, the ALU
and the CU.
Both the ALU and the CU contains
registers, which are
temporarily hold data and instructions
Different kind of CPU
Clock rate > 2GHz
Cache Memory Size
Front Side Bus
No. of transistors
RAM – Random Access Memory
RAM is volatile
data is lost when the power to the computer is
The instructions and data for the job
performing are written to RAM and read
from it as needed.
CPU can only process data in RAM
But RAM is volatile, processed data
cannot be stored in RAM
Secondary Storage device is needed
It is a non-volatile storage media which
has a big storage size.
Magnetic Media - Floppy
Plastic disk with magnetic coating
Reading and writing speed is slow
Data easily lost
Some new kind of floppy called SuperDisk
and ZipDisk have larger capacity, but need
special drives to read the disk
Magnetic Media – Hard disk
Huge storage capacity
A set of circular metal plates with magnetic
Read/write head inside
Rotate at a very high speed for faster data
Magnetic Media – Hard disk
Inside the Hard disk
Optical Media - CD
CD – Compact Disk, using laser technology
Normally it can store 640MB data.
It is cheap and durable.
Data is stored by "burning" pits and lands
on the metal coating.
A laser beam is projected to the disc
surface and the reflection will be read to
detect the patterns of pits and lands.
Optical Media - CD
The way CD read data
The way CD drive rotate the disc
Optical Media – CD-R/CD-RW
CD-R (CD Recordable) and CD-RW (CD
Both of them allow users to write data onto a
CD-R or CD-RW disc.
can be written only once
can be write and overwritten for many times.
Optical Media – DVD-ROM
It is similar to CD-ROM but its capacity
varied from 4.7GB to 17GB.
A DVD-ROM drive is needed to read
data from a DVD-ROM.
As its capacity is large, film companies
use them to publish high quality film.
Optical Media – DVD R/DVD RW
It is similar to CD-R and CD-RW, but has
a much higher capacity.
There are different standard
Different disc drives and different discs
are not compatible
Most DVD writers support RW standard
DVD-R, DVD-RW seems to be the most
It is sometimes called flash memory, where it uses
semi-conductor chips to store data.
No mechanical movement involved in data transfer,
so it is:
Quiet in operation
Not easy to be damaged
Used in portable devices such as:
PDA (Personal Digital Assistant)
The average time it takes the device to
locate data on the storage medium and
Lower access time indicates higher speed.
The unit is usually in ms.
Data Transfer Rate
The amount of data that a storage device
can move from the storage medium to the
computer per second.
Higher data transfer rate indicates higher
speed. The unit is usually measured in
It is the maximum amount of data that can
be stored on a storage medium.
The unit is usually measured in KB, MB,
An input device is any hardware that
allows a user to enter data and
commands into a computer.
Input Device – Touch Screen
A pressure sensitive display that allows
users to select options with fingers or
Not designed for inputting large amount
It is often used in information kiosk,
PDA and tablet PC.
Just like a photocopier, it sends bright
light on the document and detects the
light reflected from the source
The data detected are converted into a
Books in library and goods in supermarket
are given a unique bar code.
A bar code reader will be used for check
It is highly accurate and fast.
A user can use a microphone to input
sound into a computer.
A technology called voice recognition
can be applied to analyze the speech
An output device is a hardware that
presents digital information in a form
that human being can understand.
Output Device – CRT Monitor
It is heavy and occupies a lot of desk
Output Device – LCD Monitor
LCD monitors are thinner in size but
more expensive than CRT monitor.
Notebook computer, tablet PC have an
integrated LCD monitor.
Output Device – Inkjet Printer
It sprays tiny ink drops onto paper from
an ink-filled print cartridge. It can
produce low-cost colour printout.
Output – Laser Printer
a laser beam to produce an electronicallycharged image on a drum, causing toner to
stick to the drum whether the laser hits.
toner is transferred to the paper as the drum
presses against it and a heating process
follows which fixes the toner onto the paper.
This technology is similar to that used in a