h systems peripherals

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Peripherals Higher Computing Systems - Peripherals Infosheet 1 Produced by S Lambert, R Simpson and HSDU for City of Edinburgh Council, 2004 A peripheral is a device that can be attached to the computer processor. Peripheral devices can be external, such as a mouse, keyboard, printer, monitor or scanner. Peripheral devices can also be internal, such as a CD-ROM drive, DVD-R drive or modem. Devices are usually classified as input, output or backing storage devices. Input Devices Input can take a variety of forms, from commands you enter from the keyboard to data from another computer or device. A device that feeds data into a computer processor is called an input device. Examples of common input devices are: keyboards, mouse, joystick, digital cameras, digital video cameras, microphone and scanner Output Devices Output can also appear in a variety of forms - text, video, graphics, and so on. A device that shows data from a computer processor is an output device. Examples of common output devices are: monitors, laser printers, ink jet printers, speakers and headphones Backing Storage Devices Backing storage is a device which holds and retains data. These devices allow the user to save data in a more permanent way than RAM so that data is not lost and may be used at a later time. Examples of common backing storage devices are: hard disk drive, floppy disk drive, CD drives, solid-state devices and DVD drives Selecting the correct device There are various types of input, output and backing storage devices that are being produced by many different manufacturers. Each type of device has its own characteristics. Some devices are: faster at transmitting data can store more data are more accurate are smaller in physical size and hence portable are cheaper don’t need cables to connect to the computer So which one do you choose? Basically it all depends upon what the user requires the device to do and how much money there is to spend.

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Page 1: H Systems Peripherals

Peripherals

Higher Computing Systems - Peripherals Infosheet 1

Produced by S Lambert, R Simpson and HSDU for City of Edinburgh Council, 2004

A peripheral is a device that can be attached to the computer processor. Peripheral devices can be

external, such as a mouse, keyboard, printer, monitor or scanner. Peripheral devices can also be internal,

such as a CD-ROM drive, DVD-R drive or modem.

Devices are usually classified as input, output or backing storage devices.

Input Devices

Input can take a variety of forms, from commands you enter

from the keyboard to data from another computer or device. A

device that feeds data into a computer processor is called an

input device. Examples of common input devices are:

keyboards, mouse, joystick, digital cameras, digital video

cameras, microphone and scanner

Output Devices

Output can also appear in a variety of forms - text, video, graphics,

and so on. A device that shows data from a computer processor is

an output device. Examples of common output devices are:

monitors, laser printers, ink jet printers, speakers and headphones

Backing Storage Devices

Backing storage is a device which holds and retains data. These devices allow the

user to save data in a more permanent way than RAM so that data is not lost and may

be used at a later time. Examples of common backing storage devices are:

hard disk drive, floppy disk drive, CD drives, solid-state devices and DVD drives

Selecting the correct device

There are various types of input, output and backing storage devices that are being produced by many

different manufacturers. Each type of device has its own characteristics. Some devices are:

faster at transmitting data

can store more data

are more accurate

are smaller in physical size and hence portable

are cheaper

don’t need cables to connect to the computer

So which one do you choose? Basically it all depends upon what the user requires the device to do and

how much money there is to spend.

Page 2: H Systems Peripherals

Backing Storage

Higher Computing Systems - Peripherals Infosheet 2.1

Produced by S Lambert, R Simpson and HSDU for City of Edinburgh Council, 2004

Magnetic disks Magnetic discs are one of the most popular forms of Direct Access storage. There are a variety of

different types of magnetic disc.

Floppy Disc Portable 3.5 inch discs which require a 3.5 inch disk drive. Limited

capacity of 1.4 Mb means that they are very rarely used.

Zip Disc Slightly physically bigger discs than a floppy disc with a larger capacity of

750 Megabytes and a faster access time.

Hard Disc Drive Sealed set of discs built-in to computers. Has fastest access time of any

storage device, 70 Megabytes per second, and is also the most difficult to

damage. Has capacities ranging from 120 Gigabytes to 2 Terrabytes.

Portable (External) Hard Disc Drive Small portable hard disc drives are very similar to the hard disc drives

supplied with most desktop computers with the addition that they are

portable. They usually come with USB connections and can have the same

access speeds and capacities as the internal drives. Not as robust as the

internal versions and require careful handling.

Magenetic Tape Tape has been used as a backup medium in commercial situations for many years. It is very cheap and

secure. Its main disadvantage is the serial nature of access which makes it very slow to access data unless

it has first been sorted. There are many different types of tape technologies.

8mm tape

This format was originally designed for the video industry but it has been adopted by the computer

industry as a reliable way to store large amounts of computer data. Tapes can store up to 14Gb with

access speed's of 1 Mb/sec.

Digital Audio Tape (DAT)

DAT was originally conceived as a CD quality audio format. In 1998, Sony and HP

defined the DDS (Digital Data Storage) standard, transforming the format into one that

could be used for computer data storage. This technology uses a 4mm tape which

employs a technique called helical scan recording. This is the same type of recording as

that used in video tape recorders and is slower than the linear type. For this reason, it is

generally only used in environments where high capacity is the primary requirement.

Tapes can store up to 40Gb and have access speeds of 2 Mb/sec.

Digital Linear Tape

DLT technology started in 1989. DLT is like the old reel to reel magnetic

recording method where the tape cartridge performs as one reel and the tape

drive as the other. Tapes can store up to 70 Gb with access speeds of 20 Mb/sec.

Page 3: H Systems Peripherals

Backing Storage

Higher Computing Systems - Peripherals Infosheet 2.2

Produced by S Lambert, R Simpson and HSDU for City of Edinburgh Council, 2004

Optical Drives

Optical technologies involving the use of lasers have contributed to the production of

CD, DVD and blu-ray drives. A plastic disc is scanned using a laser which reflects off

pits on the surface of the disc differently from areas where there is no pit. All formats

of optical drives use the same physical size of plastic disc. Most drives can read a

variety of formats e.g. Blu-ray drives can read DVD and CD discs.

Compact Discs These have a capacity of approx 700 Mb

CD-ROM drives allow different types of CD’s to be read.

CD-R drives allow CD-ROMs and audio CDs to be written. CD-R software is also

required to enable the CD to be ‘burned’.

CD-RW drives enables CDs to be written onto it in multiple

sessions. One of the problems with CD-R disks is that you can

only write to them once. With CD-RW drives and disks, you can

treat the optical disk just like a floppy or hard disk, writing data

onto it multiple times.

Usually speeds for CD drives look like 12x2x24x (three numbers separated by the letter "x"),

these numbers indicate the speeds of the drive. The "x" stands for the transfer of 150 Kb of data

per second, and each number represents a different action that the drive can carry out. For

example, a CD-R drive has two actions, recording onto and reading from compact disks. A CD-

RW drive has three actions, recording, rewriting (erasing and recording over) and reading. When

looking at the drive speeds, the first number indicates the speed at which the drive will record

data onto a disk. So, in the above example, the drive will record data at 12 times 150 Kb/s. The

second number indicates the speed at which the drive will rewrite data onto a disk. So in the

above example, the drive will rewrite data onto the compact disc at 2 times 150 Kb/s. Typically,

the second number, the rewrite speed, is lower than the first number, the write speed, because

rewriting is a slower process than writing. The last number indicates the speed at which the drive

will read data from a compact disk. So in the above example, the CD drive will read data from a

compact disc at 24 times 150 Kb/s.

Digital Versatile Discs DVD's are very similar to compact discs but have larger capacities of either 4.7

Gb or 8.4 Gb.

Blu-ray This is the next generation of optical disc format. Although physically the

same size as a DVD it can store either 27Gb (single layer) or 54Gb (double

layer). It's increased capacity comes from using a laser beam(Blue) that is

narrower than the laser beam (Red) used on CD's and DVD's. It's access

speeds range from 4.5 Mb per second to 54 Mb per second.

Page 4: H Systems Peripherals

Backing Storage

Higher Computing Systems - Peripherals Infosheet 2.3

Produced by S Lambert, R Simpson and HSDU for City of Edinburgh Council, 2004

Solid State Technology

Solid-state devices are made from flash ROM which is a type of Electrically

Erasable Programmable Read-Only Memory (EEPROM). It is physically

very small, have no moving parts, use very little power and are unaffected by

vigorous movement. They have become increasingly popular and are now the

standard storage device for photographs on digital cameras, music on MP3

players and portable data storage devices (USB pens). They are also becoming

the preferred storage device on laptops, replacing the hard disc drives. Once

the capacity increases and the price reduces they may replace hard disc drives

on all personal computers.

Flash Cards

These are mainly used for data storage in digital cameras and mobile phones. They come in a variety

of different sizes and standards which include -

Compact Flash (CF)

Secure Digital (SD)

Memory Stick/Pro

XD-Picture Card

USB Flash Memory

A USB flash memory is flash ROM with a USB plug. You

plug it into your computer, copy the file onto it, then simply

plug it into the USB socket of another computer and access the

file. They are small enough to attach to a keyring and are

difficult to damage. Most USB flash memory is plug and play,

once it is plugged into a USB port the computer will

automatically recognise it and display it on your desktop. Files

are stored on it simply by dragging and dropping them onto the

icon. Storage Capacities start from 128 Megabytes to 256

Gigabytes. Flash drives also are called pen drives, key drives

or simply USB drives. USB flash memory has replaced floppy

discs as a portable storage system.

Memory Card Reader/Writer

These can be used with most of the memory card formats to allow the

cards to be used as a file transfer medium similar to the USB Flash

Memory. The reader/writer is connected to a USB port and once a

memory card has been connected is identified by the system as an

external drive. Files can simply be dragged and dropped to transfer

data. Once full/empty the card is simply removed and another fitted.

This is useful as it allows memory cards from digital cameras etc to be

removed and used without the camera being connected to the computer.

Page 5: H Systems Peripherals

Development Trends In Backing Storage

Higher Computing Systems - Peripherals Infosheet 2.4

Produced by R Simpson Queensferry High School, 2009

Increased Capacity Hard Disc drives have increased in size dramatically. In thirty years they

have gone from 10 Mb to 2 Tb - almost a factor of a million times larger.

Solid-state drives have now increased to 512 Gb and should be matching

Hard Disc Drive capacities within a few years. Solid-state portable

devices are now available up to 64 Gb from 8 Mb 10 years ago. Optical

storage devices are increasing with blu-ray discs able to store 200 Gb,

although 50 Gb is still the commercial norm.

Increased Read / Write Speeds The time it takes to read and write data to storage devices has been increasing with every new

development. Each time a new improved version of a storage drive is produced they have increased the

access times. Hard disc drives can now access data at speeds of up to 125

Megabytes per second, USB Flash memory at 30 Megabytes per second and DLT

tape at 20 Megabytes per second. As well as the devices accessing the data faster

than before, the interfaces that they are using allow faster access to the data. USB 2

has access speeds of 60 Megabytes per second while Firewire 800 has an access

speed of 100 Megabytes per second.

Reduced Physical Size Hard disc drives are becoming physically smaller but with larger capacities. In 1980 the Seagate company

produced a 5.25 inch drive, in 1987 the Conner company produced a 3.5 inch drive, in 1999 IBM

produced a 1 inch drive and in 2004 Toshiba were using 0.85 inch drives for use in mobile phones and

laptops. Each time the physical size was reduced the capacity of data that the drive could

hold was increased. Some solid-state devices such as SD cards are now available in

micro forms which are half the physical size for use with mobile phones. The physical

size of other storage devices such as optical discs and USB pens haven't changed greatly.

Lower cost per unit of storage The costs of storage are decreasing rapidly. In 1995 a Megabyte of storage on a hard disc drive would cost

you £ 300, today the prices are extremely low - e.g.

USB Flash drive £ 2.50 per Gb

Internal Hard Disc Drive £ 0.05 per Gb

External Hard disc drive £ 0.06 per Gb

DVD-R disc £ 0.03 per Gb

CD-R Disc £ 0.10 per Gb

Implications

The implications of this fast changing environment are that backup has become very cheap and simple, so

less data should be lost. As each new improvement in the technology comes along then there are

implications for the computers that we are using in that they may not have the correct new interfaces. This

is not usually a problem as the steep decrease in prices means that we are more likely to buy new

computers every five years than try to upgrade them. This has environmental impacts as we dump more

and more old hardware. A safe, world-wide re-cycling policy for old equipment is required.

Year Hard Disc

Capacity

1980 10 Mb

1991 100Mb

2005 500 Gb

2007 1 Tb

2009 2 Tb

Page 6: H Systems Peripherals

Interfacing Peripherals

Higher Computing Systems - Peripherals Infosheet 3.1

Produced by S Lambert, R Simpson and HSDU for City of Edinburgh Council, 2004

Computer peripherals such as disc drives, printers, mice etc all work in totally different ways and linking

them to the processor is a difficult task. They all work at different speeds, use different codes, transfer

different amounts of data at a time and even work at different voltages.

Interfaces The interface is the link between the processor

and the peripheral. Its task is to transfer data

so that the processor is delayed as little as

possible.

The following may have to be completed

before communication can happen:

Data Format Conversion This involves changing the data received from

a peripheral into a form that the processor

understands. This could include serial to

parallel and/or analogue to digital conversion.

Serial Transmission

This is when a single line is used to transmit

bits, one at a time.

Advantages

Good for transmission over long distances and

only one data channel required.

Disadvantages

More time required (8 time units instead of 1)

Start and stop bits required to identify different

data words.

Parallel Transmission

This is when several bits are transmitted

simultaneously over several lines. Parallel

transmission is used extensively within the

computer for high speed data transfers on

various buses.

Advantages

Good for transmission over short distances

Disadvantages

Skewing can occur.

Signals degrade with distance and interference.

Data Bus

Address Bus

Control Bus

Interface1 Interface2

Peripheral Peripheral

Processor

Memory

unit of data

one

wire

for

each

bit

unit of time

skew

1

0

0

1

1

0

1

1

1

fig19

1

1 0

time

one character

10 01 11 0 10

start bit

7 data bits

parity bit

stop bits

direction of transmission

fig20

Page 7: H Systems Peripherals

Interfacing Peripherals

Higher Computing Systems - Peripherals Infosheet 3.2

Produced by S Lambert, R Simpson and HSDU for City of Edinburgh Council, 2004

Analogue Signals

signals from devices such as microphones are analogue. If

you could see an analogue signal it would be constantly

varying.

Digital Signals

Computers can only work with digital signals which have

only two values. This is usually represented by a 1 or a 0.

Analogue to Digital and Digital to Analogue Converters

These converters change the analogue signals to digital or

vice versa. An example would be to take the analogue signals

from a microphone and convert them into digital to be stored

on a computer system.

Status Information The purpose of status information is to show whether a peripheral is ready to communicate. Status

information on a printer will show whether a printer is ready or not to receive data.

Device Selection The recognition of device information. Device codes are used to distinguish between different peripherals.

This is a number code which allows the processor to identify and select a particular peripheral.

Voltage Conversion This is required when a peripheral operates using a different voltage from that of the processor. The

voltage used by the peripheral must be converted to that used by the motherboard.

A protocol is a standard that enables communication between a computer system and it's peripherals. If

the protocols are different between the system and the peripheral they must be converted to enable

communication.

International Standards A number of international standards have been designed for interfaces so that peripherals can be

connected to computers with these standards. For example most computers are equipped with USB

interfaces. These means that if peripheral makers use this internatioal standard interface then most

computers will be able to use the interface.

USB - Universal serial Bus

SCSI - Small Computer Systems Interface

SATA - Serial Advanced Technology Attachment

MIDI - Musical Instrument Digital Interface

IEEE(Firewire) - Institute of Electrical and Electronic Engineers

PCI - Peripheral Component Interconnect

Centronics

RS 232 - Recommended Standard

Page 8: H Systems Peripherals

Interfacing Peripherals

Higher Computing Systems - Peripherals Infosheet 3.3

Produced by S Lambert, R Simpson and HSDU for City of Edinburgh Council, 2004

Current Trends of Interface Speeds Many different factors have contributed to the improvement in computer

system performance. The speed of interfaces is one of them. Due to the

amount of data required to be sent and received from peripherals to the

CPU, how much data that can be sent per second is an important factor.

The introduction of multimedia with memory intensive media types has led

data rates to rise to multi Gigabyte levels.

Below is a table showing speeds of different types of interfaces:

I/O Interface Maximum Speed (Megabytes/sec.)

Standard Parallel 0.15

USB 1 1.50

USB 2 480

SATA 1500.00

Serial ATA III 600.00

IEEE (Firewire 400) 400

IEEE (Firewire 800) 800

SCSI 2 Wide 20.00

Ultra 320 SCSI 320.00

Most users expect their computers systems to deal with large amounts of data at high speeds. Increasing

interface speeds is one factor that will allow computers to perform better.

Wireless Communication between Peripherals And CPU Users are demanding greater degrees of portability in Personal Digital Assistants (PDAs), mobile phones,

laptop computers, digital cameras, and MP3 players, to name but a few. However, this trend stretches the

devices' abilities to meet performance requirements, while at the same time being packaged into smaller

and lighter form factors and consuming less power in order to increase battery life.

Some peripherals now have the ability to communicate with the CPU without

physical connection (i.e. cabling).

Bluetooth is an example of wireless technology. It is a short range radio

technology aimed at simplifying communications among Internet devices and

between devices and the Internet. It also aims to simplify data synchronisation

between Internet devices and other computers.

Wireless telecommunications holds particular promise for people with disabilities because it enhances

both mobility and communications, two functions that are often challenging for people with certain kinds

of disabilities. Ordinary cordless telephones have long been useful devices for

people who have mobility disabilities and cannot rush to the telephone.

Similarly, mobile telephones have been valuable safety devices for people

with mobility disabilities traveling alone, and they can help compensate for

the lack of accessibility of many pay telephones. Pagers and other wireless

data communications systems have been used for communicating with deaf

persons.

Page 9: H Systems Peripherals

Buffers And Spoolers

Higher Computing Systems - Peripherals Infosheet 4

Produced by S Lambert, R Simpson and HSDU for City of Edinburgh Council, 2004

In general a buffer or spooler will be used when a fast acting part of a system is exchanging data with a

slow acting device. Then buffer or spooler is used to store data until the data can be dealt with. This

ensures that the processor is not held up by slow communications to and from peripherals.

Buffers

Buffers are a piece of memory used to store information temporarily. Most

interfaces have buffers to store blocks of data while in transfer between the

processor and the peripheral. The buffer must also keep the status of the

peripheral so that the processor knows when it is able to send or receive data

and when problems arise.

Example

Printing might involve (if the file is too big for the buffer to handle in one go):

• the processor checking with the interface to see if the printer is ready

• the interface sending back an OK

• the processor sending data to the interface

• the interface saying its buffer is full

• the interface sending data to the printer

• the interface saying to the processor that it is ready to accept more data.

These steps will be repeated until all the data is sent.

Peripheral Buffers

Most peripherals have buffers of their own (device based) and some interfaces and

peripherals often have their own processors to control their operation. Some laser printers

have a better processor and more memory than the computer its connected to.

Spoolers

Another approach to ensuring the

processor is not held up by slow

peripherals is to send data to be

spooled. This means that the data is

sent to fast backing storage usually a

disc. This is preferred to buffering

when large amounts of data is to be

sent or if the peripheral is shared across

a network. In a spooled system, data is

sent to backing store and fed to the

peripheral in the gaps between processing actions (an example of this is background printing). In this

way, it is very often possible for the peripheral to operate continually during a program and for the action

of the computer also to appear continuous.

Buffers versus Spoolers

An advantage of spoolers over buffers is that buffers usually have a small fixed size but the spollers are

using a hard disc drive which has a much greater capacity.

In practice spoolers and buffers are used together when printing.

Page 10: H Systems Peripherals

Selecting Hardware

Higher Computing Systems - Peripherals Infosheet 5.1

Produced by S Lambert, R Simpson and HSDU for The City of Edinburgh Council 2004

Obviously there is a wide range of devices that can be used with computers. So which ones do you

choose? Basically it is down to the task that needs to be solved. Typical questions that could be asked

are:

Are graphics and/or photography required?

How much backing storage?

What type of print outs are necessary?

How will the data be displayed?

What are the RAM requirements?

Is processor performance important?

Are there specific peripherals that are required?

As the cost of tackling problems using computer hardware can be a costly one, it is necessary to be able to

justify why choices have been made.

Here are typical tasks that a computer system with specific peripherals could solve.

Production of a multimedia catalogue

Setting up a LAN in a school

Development of a school website

Creating an audio CD

Here are possible solutions to three of these typical tasks:

Production Of A Multimedia Catalogue

Multimedia involves the use of media elements, such as text, graphics, sound, video and animation. The

computer system itself must be of a good specification to create, edit and run these elements. So typical

minimum hardware could be:

Hardware Justification Computer System with:

256 RAM To open media elements and run software

1 GHz Processor To run applications quickly and view video at an

appropriate speed

20 Gb Hard disk drive To store programs and media elements

CD-RW drive To load software and save catalogue onto

Firewire interface To attach camera and capture video

Video card To capture and playback video elements

Sound card To capture and playback audio

High resolution monitor To view media elements

Digital video camera To record video frames

Microphone To record audio

Mouse and keyboard To input characters and control selection of

elements

Scanner To capture still images

High resolution colour laser printer To print out multimedia catalogue

Speakers To playback audio

Page 11: H Systems Peripherals

Selecting Hardware

Higher Computing Systems - Peripherals Infosheet 5.2

Produced by S Lambert, R Simpson and HSDU for The City of Edinburgh Council 2004

Setting Up A Local Area Network (LAN) In School

Setting up a network would require many desktop computers

to be linked together. Possible hardware for this task could be:

Hardware Justification 50 Computer Systems with:

64 RAM To open media elements and run software

500 MHz Processor To run software at an appropriate speed

10 Gb Hard disk drive To store programs

CD-ROM drive To load networking software

Network Interface Card (NIC) To allow computer to be connected to the network

Monitor To view data

Cables To allow computer to be connected to the network

Mouse and keyboard To input characters and control selection of

elements

Hubs To connect devices on the network

Switches To filter and forward packets

Network laser printer To print documents across the network

Network server To store users’ files across the network

Development Of A School Website

Creating a school website could possibly involve using multimedia elements, so a

higher specification computer system is required. Also possible Internet access

may be a requirement. Possible hardware for this task could be:

Hardware Justification

50 Computer Systems with:

256 RAM To open media elements and run software

1 GHz Processor To run software at an appropriate speed

20 Gb Hard disk drive To store programs

CD-ROM drive To load networking software

Network Interface Card (NIC) To allow computer to be connected to the network

Video card To capture and playback video elements

Sound card To capture and playback audio

High resolution monitor To view data

Cables To allow computer to be connected to the network

Mouse and keyboard To input characters and control selection of

elements

Digital video camera To connect devices on the network

Scanner To capture still images

Ink jet printer To print out completed pages for checking

Digital camera To take digital photographs