Hardware/Peripherals
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Hardware and peripherals are basically computer devices which add additional functionality to a PC.
A Computer System is made up of a number of types of device.
Computer devices are sometimes called Peripherals which are attached to the Central Processing Unit.
INPUT DEVICES
Used to enter information into the computer system
Mouse
Used to point and select. Also used to draw.
Keyboard
Used to enter text when word processing.
Scanner
Used to input a photograph or graphic. ( A4 flatbed or hand-held )
Other Input devices
Graphics Tablet ( Digitiser )
Digital Camera
Joystick
Microphone
Touch Screen
Bar-Code Reader
Magnetic Strip Reader
OUTPUT DEVICES
Used to display information which has been input & processed
Monitor ( Visual Display Unit )
Screen Display of a data-base enquiry.
Printer
Hard Copy ( Paper) of a word Processed letter.
Plotters
Used to produce accurate plans from a CAD system.
Speakers
Used with a multimedia system.
TYPES OF PRINTER
Laser
Advantages
High speed and excellent quality.
Disadvantages
Expensive ( But prices are falling )
Operation
Printer works similar to a photocopier using toner.
lnkjet
Advantages
Much cheaper than a laser printer to purchase and inexpensive for colour printouts.
Disadvantages
Expensive to run as ink-cartridges have to be replaced frequently.
Quality not quite as good as laser.
Operation
Works by squirting ink at the paper.
Dot-Matrix
Advantages
Cheap to purchase and run.
Best used in situations where exact carbon copies are needed ( Invoices )
Disadvantages
Poor quality output and noisy.
Operation
Impact printer. Ribbon imprints characters onto paper.
STORAGE DEVICES ( ALSO KNOWN AS BACKING STORAGE )
Used for long term ( permanent ) storage. Sometimes called auxiliary storage.
Floppy Discs Drive - Each Disc has 1 .44 MegabyteS of storage.
Floppy discs are used to install software and take copies of data-files.
Hard Disc Drive - 1 Gigabyte or more
This is used to store programs ( software ) and save data-files for daily use
Tape Drives - 2 Gigabytes or more
Mainly used to make backups of the data on hard disc drives
CD-ROM ( Optical Storage ) - Compact Disc Read Only Memory
Used to store multimedia information ( Text, Sound & Video ). Information can't be changed.
Zip Drives - 100 & 250 Megabyte Disc Cartridge
Jaz Drive - High speed tape drive that compresses data before storing.
TYPES OF FILE ACCESS - SERIAL AND DIRECT
Tape storage is slow
Reading data from tape storage takes a long time because you have to go a lot
of tape to find the data needed. This is known as serial access. The data
is often stored in order - sequentially.
Disc storage is fast
Reading data from disc is fast because the disc heads can move straight to
the data. This is known as Direct Access. It is sometimes called Random Access.
OTHER USEFUL INFORMATION ON DATA STORAGE
Storage size is measured in Bytes
1 BYTE = a character - the letter a - A Byte = 8 Binary Digits
1 Kilobyte (KB) = 1024 Bytes
1 Megabyte (MB) = 1048576 Bytes ( Roughly 1 million characters )
1 Gigabyte = 1000 Megabytes
Disc and Tape devices uses a Magnetic Surface to store data.
CD-ROM uses light ( laser ) optic technology to store data.
Magnetic Tape is used by companies to archive data.
Tapes are cheap (?5) and can be used to sore at least 2 Gigabytes of data.
Getting a data file from disc is known as "Reading"
Saving data to disc is known as "Writing"
The speed at which data can be read from a storage time is known as the
"Access Time" and is usually measured in millionths of a second.
Floppy Discs are magnetically divided into Tracks and Sectors during the process of FORMATTING.
A Hard disc drive is made up of many layers of disc surfaces.
Disc Drives use a File Allocation Table ( FAT ) as an index to locate data-files
on disc. The File Allocation Table stores the address of a data-file - the
address holds the track and sector number.
Data on disc & tape can easily be corrupted or deleted.
This can happen by:
Exposure to a Magnetic Field
Disc Heads collide with the surface of the disc.
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Date: Fri, 28 Jul 2006 Time: 12:00 AM
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