1. Nat 4/5 Computing Science Input, Output and Backing Storage
Computer Systems
Nat 4/5 Computing Science
Input, Output and Backing Storage

2. 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

4. Nat 4/5
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

6. Backing Storage

7. a group of 8 bits – Single Letter
Nat 4/5
Storage Terms
Term
Abbreviation
Description
Bit
binary digit, 0 or 1
BIGGER ->
Byte
a group of 8 bits – Single Letter
Kilobyte Kb
1024 bytes
Megabyte Mb
1024 Kilobytes
Gigabyte Gb
1024 Megabytes
Terabyte Tb
1024 Gigabytes

8. Types Of Access Sequential Access Direct/Random Access
Nat 4/5
Types Of Access
Sequential Access
Direct/Random Access
To go from file A to file Z in a sequential-access system, you must pass through all files in order.
Sequential access is sometimes called serial 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

9. 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
Floppy Disks/Hard Disk Drives
Magnetic Tapes
Optical
These store data by means of lasers ‘burning’ a disk
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

11. Hard Disk Drives (HDD’s)
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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

12. Magnetic Tape Magnetic tapes are essentially the same as music tapes.
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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

13. Optical Storage – CD/DVD
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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

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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+

15. Summary There are three main types of backing storage
Optical
Magnetic
Solid State
There are two main types of access
Sequential
Direct/Random
Input Devices put information INTO the computer
Output Devices get information FROM the computer