S2 Computer Literacy

Computer Hardware

Overview of Computer Hardware

MotherboardCPURAMHarddiskCD-ROMFloppy DiskDisplay CardSound CardLAN Card

MotherboardIt 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

CPUA CPU consists of two parts, the ALU and the CU.Both the ALU and the CU contains registers, which are

high-speed memory temporarily hold data and instructions during processing.

Different kind of CPUIntel

CeleronPentium 4Xeon

AMDDuronAthlon XPSempronAthlon 64

Common features

Clock rate > 2GHz

DifferencesWord SizeCache Memory SizeFront Side BusNo. of transistors

RAMRAM – Random Access MemoryRAM is volatile

data is lost when the power to the computer is turned off

The instructions and data for the job performing are written to RAM and read from it as needed.

Secondary StorageCPU can only process data in RAMBut RAM is volatile, processed data cannot be stored in RAMSecondary Storage device is neededIt is a non-volatile storage media which has a big storage size.

Secondary Storage

Magnetic Media - FloppyFloppy

1.44 MBPlastic disk with magnetic coatingReading and writing speed is slowData easily lostSome new kind of floppy called SuperDisk and ZipDisk have larger capacity, but need special drives to read the disk

Magnetic Media – Hard disk

Hard diskHuge storage capacityA set of circular metal plates with magnetic coatingRead/write head insideRotate at a very high speed for faster data access

Magnetic Media – Hard disk

Inside the Hard disk

                                                                                                  

                                              

                                                                                   

                                                          

Optical Media - CDCD – Compact Disk, using laser technologyNormally 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 dataThe way CD drive rotate the disc

Optical Media – CD-R/CD-RW

CD-R (CD Recordable) and CD-RW (CD Rewriteable)

Both of them allow users to write data onto a CD-R or CD-RW disc.

CD-Rcan be written only once

CD-RWcan be write and overwritten for many times.

                                                                                     

                                                       

Optical Media – DVD-ROMIt 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

DVD+R, DVD-RDVD+RW, DVD-RWDVD-RAM

Different disc drives and different discs are not compatibleMost DVD writers support RW standardDVD-R, DVD-RW seems to be the most popular standard

Semi-conducting Media 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 operationNot easy to be damaged

Used in portable devices such as:PDA (Personal Digital Assistant)MP3 playerDigital camera

Semi-conduction MediaCF card

SD card

Memory Stick

Flash Thumb Drive

Card Reader

Measuring SecondaryStorage device

Access timeThe average time it takes the device to locate data on the storage medium and read it.Lower access time indicates higher speed. The unit is usually in ms.

Measuring SecondaryStorage device

Data Transfer RateThe 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 MB/s.

Measuring SecondaryStorage device

Storage CapacityIt is the maximum amount of data that can be stored on a storage medium.The unit is usually measured in KB, MB, and GB.

Measuring SecondaryStorage device

Input DeviceAn 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 stylus.Not designed for inputting large amount of text.It is often used in information kiosk, PDA and tablet PC.

ScannerJust like a photocopier, it sends bright light on the document and detects the light reflected from the source document.The data detected are converted into a digital graphics.

Barcode ReaderBooks in library and goods in supermarket are given a unique bar code.A bar code reader will be used for check out.It is highly accurate and fast.

Voice InputA user can use a microphone to input sound into a computer. A technology called voice recognition can be applied to analyze the speech into text.

Output DeviceAn 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 space.

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 Printera laser beam to produce an electronically-charged 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 photocopying machine.