Computer
Systems
Nat 4/5 Computing Science
Input, Output and Backing
Storage
Lesson Aims
 By
the end of this lesson:
 Pupils will be able to:
 Describe the features, functions and uses of:
 keyboard, mouse, microphone, touchpad, digital
camera, scanner, webcam
 Describe the features, functions and uses of
 monitor, LCD panel, inkjet and laser printers,
loudspeakers
 Compare devices using appropriate characteristics
including
 resolution, capacity, speed of data transfer, cost
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Input Devices
 An
input device is a device which creates
some new information to put INTO the
system
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Output Devices
 An
output device is a device which gets
information FROM the system
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Input/output Devices
 You
have to be able to compare these
devices in terms of appropriate
characteristics such as:




Resolution
Capacity
Speed of data transfer
Cost
Backing Storage
Nat 4/5
Storage Terms
Term
Abbreviation
Description
binary digit, 0 or 1
Byte
a group of 8 bits – Single Letter
Kilobyte
Kb
1024 bytes
Megabyte
Mb
1024 Kilobytes
Gigabyte
Gb
1024 Megabytes
Terabyte
Tb
1024 Gigabytes
BIGGER ->
Bit
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Types Of Access
Sequential Access


To go from file A to file
Z in a sequentialaccess system, you
must pass through all
files in order.
Sequential access is
sometimes called serial
access
Direct/Random Access


Refers to the ability to
access data at random. In a
random-access system, you
can jump directly to file Z.
Disks are random access
media, whereas tapes are
sequential access media
Nat 4/5
Backing Storage


Backing storage is used to save permanent copies
of your files onto.
There are 3 main types
 Magnetic

These use magnetic fields to store the data



Optical

These store data by means of lasers ‘burning’ a disk


Floppy Disks/Hard Disk Drives
Magnetic Tapes
CDROM/DVD/Blue Ray
Solid State

This uses no moving parts at all, uses memory chips


USB Drives
SSD Hard Drives
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Floppy Disks

Floppy Discs are small pieces of plastic film wrapped
in a plastic case, they are fast becoming very scarce
due to their slow transfer speed and limited
capacity, have basically been replaced with USB
Flash Drives
Type Of Access
Direct/Random
Capacity
1.44 Megabytes
Portability
Very – Only requires another drive
Transfer Rate
Very Slow – 500Kbps
Price
Approx 25p per Disk
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Hard Disk Drives (HDD’s)
 Hard
Disk Drives are usually stored inside the
computer. They use disks of metal which are
magnetically charged.

These are read by a small head – like a
record player, which moves over the disks.
Type Of Access
Direct/Random
Capacity
Up to 3TB
Portability
Not portable
Transfer Rate
Up to 600Mbps
Price
Approx £40 - £220
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Magnetic Tape
 Magnetic
tapes are essentially the same as
music tapes.

To access a file you have to sequentially go
through every file by fast forwarding or
rewinding.
 They
are however relatively cheap and
easy to store.

Often used for backups
Type Of Access
Sequential
Capacity
Up to 80GB
Portability
Very portable, requires another drive
Transfer Rate
Up to 7Mbps
Price
Up to £20 per tape
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Optical Storage – CD/DVD

CD and DVD’s are optical media – a laser is used to
burn holes (pits) into the surface of the disk.


CD/DVD-R are recordable once
CD/DVD-RW are rewritable more than once
Type Of Access
Direct/Random
Capacity
CD: 700MB (80 minutes audio)
DVD 4.7GB up to 50GB Blue Ray
Portability
Very portable, requires another drive
Transfer Rate
Approx 130Mbps
Price
CDR: 20-30p DVDR: 30p-£1
Nat 4/5
USB Flash Drives

USB (Universal Serial Bus) flash drives use memory
chips to store data, this means there are no moving
parts at all – this is called solid state storage, this
means they are very robust.


These are often used in MP3 – Players – Ipod
Nano/Shuffle uses this.
Some are even waterproof or branded with company
logos
Type Of Access
Direct/Random
Capacity
Up to 128GB
Portability
Very portable, only requires USB port
Transfer Rate
10-30MBps
Price
£10-£100+
Summary
 There



Optical
Magnetic
Solid State
 There


are three main types of backing storage
are two main types of access
Sequential
Direct/Random
 Input
Devices put information INTO the
computer
 Output Devices get information FROM the
computer