Software Reliability

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A2 ICT
Module 5
14.10 Portability of Data
PART 1 - Introduction
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Objectives

• Protocols and Standards explain the need for
  portability of data ease of transferring
  numerical, graphical and textual data between
  applications.
• Describe the need for standards for interchanging
  numerical, graphical and textual data between
  different hardware and software platforms.

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Contents.

• Communication Standards understand why protocols
  are required and know of the existence, benefits
  and limitations of standards.
• Understand the protocols and addressing
  mechanisms used to support the World Wide Web.
• Emergence of Standards recognise the existence
  of de facto standards based on historic precedent
  and sales success in comparison to formal
  standards.

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Definition

• The ease with which data can be transferred from
  one computer system to another. There are a
  number of factors which can affect portability
  including
• The operating system on each machine
• The application (and its version) being run on
  each machine

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A2 ICT
Module 5
14.10 Portability of Data
PART 2 - The Need for Data Portability
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Four Situations where Data Portability might be
required

• If you want to transfer a file that has been
  created using one package to a completely
  different package
• Word -gt Word Perfect
• Use of ASCII, RTF
• Conversion programs/modules

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Data Portability (cont/d)

• Where files created using one software package
  run on one type of hardware need to be
  transferred to the same package running on
  different hardware
• Hardware platforms e.g. Windows to Apple Mac.
• Changes in media
• Conversion programs/modules

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Data Portability (cont/d)

• Where the files were created by different
  versions of the same package.
• Loss of features
• Often able to revert to old format
• Conversion programs/modules can cause some issues

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Data Portability (cont/d)

• Where a file in one type of software needs to be
  transferred or used by another type of software.
• Importing pictures into word processed document
• CSV and other data export formats
• Conversion programs/modules can cause some issues

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The Need for Data Portability

• Not everyone uses the same hardware and software
• Some hardware and software perform specific
  functions
• Editors of journals ask for already word
  processed manuscripts from authors to avoid
  further errors occurring why?

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The Need for Data Portability

• New machines and preloaded software in businesses
• Moving up a version can be easier, but going the
  other way can cause problems
• Cost involved
• Need to make sure software sells and can import
  data from previous version (avoids re-keying of
  data etc.)

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A2 ICT
Module 5
14.10 Portability of Data
PART 3 Protocols and Standards
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Communications Software

• Allows computers to communicate with each other,
  controlling transmission by specifying
• Speed of transmission
• Direction of data flow
• Method transmission
• Which computer code is used (e.g. ASCII, EBCDIC)
• Type of parity used (e.g. odd or even)
• These rules and procedures form the
  communications protocol

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Speed of Transmission

• The term bandwidth is often used to represent the
  speed of transmission
• The link between two computers is known as a
  channel, and could be
• A telephone line
• A fibre-optic or coaxial cable
• A microwave or satellite link

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Speed of Transmission

• Channel Bandwidth
• Baseband
• carries one signal at a time
• 0 or 1 indicated by presence / absence of voltage
• very fast but only over short distances.
• Broadband
• multiple signals on a fixed carrier wave
• 0 and 1 sent as variations on this wave
• data, audio and video transmission simultaneously

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Speed of Transmission

• Speed
• expressed as baud rate, in bits per second (bps).
  
• Framing bits
• each data byte uses 7 or 8 bits,
• may have start and stop bit and/or parity bit
  added
• Thus each character may need 10 bits, so a speed
  of 56,000bps means about 5,600 characters a
  second.

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Modems

• Modem (Modulator/Demodulator)
• Telephones designed for speech (analogue signal)
• Modems at either end convert digital-analogue and
  then analogue-digital.
• Typical transmission rates of between 9,600 and
  56,600 bps

modem
modem
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Direction of Transmission

• Simplex - data can flow in one direction only.
  Electronic notice-boards that receive and
  display information about, for example, train
  arrival times could use a simplex line, since
  communication is one-way only
• Half-duplex - data can flow in both directions,
  but not at the same time, like a CB radio
• Full-duplex - data can flow in both directions at
  the same time like a telephone line where two
  people can both be talking at once.

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Serial Transmission

• Bits are transmitted one at a time over single
  channel. Two types of serial mode for sending
  data
• Asynchronous transmission
• one character at a time, with a start and stop
  bit sent with each character
• generally for lower speed transmission e.g. LAN
• Synchronous transmission
• enables whole blocks of data to be sent in timed
  sequences
• much faster

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Parallel Transmission

• All the bits making up a character, together with
  a parity bit (if used) transmitted simultaneously
• It is limited to short distances of a few metres,
  e.g. between a computer and printer.

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Telecommunications Standards and Protocols

• To allow machines from different manufacturers to
  communicate with each other over local or wide
  area networks, it is necessary to define
  standards
• Advantages of standards
• can create networks containing hardware from
  different vendors (such as Apple and IBM)

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Telecommunications Standards and Protocols

• Disadvantages of standards
• may disallow certain features or capabilities
  that are valuable in a particular situation but
  inconsistent with the standard.
• may also prohibit features which certain vendors
  have built into their hardware in order to steal
  a march on the competition something that is
  better than other architectures but will not work
  with other hardware.
• In spite of this, most people would rather have
  hardware that has less than the maximum
  capabilities but is compatible with their other
  hardware.

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Standards (cont/d.)

• Use of common operation system Windows with a
  common clipboard allows information to be
  transferred around the package

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A2 ICT
Module 5
14.10 Portability of Data
PART 4 Addressing and the WWW
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Internet Protocols

• TCP/IP - (Transport Control Protocol / Internet
  Protocol)
• Has become de facto standard
• World Wide Web Addressing
• Internet Service Provider (ISP)
• has unique IP (Internet Protocol) address
• four numbers separated by full stops
• Domain Name System (DNS)
• translates IP address numbers into domain name
• URL (Uniform Resource Locator)
• standard address used to find a page

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Addressing of WWW

• Part 1 - Transfer Protocol
• http// Hypertext Transfer Protocol
• https// Hypertext Transfer Protocol, Secure
• ftp// - File Transfer Protocol for FTP site.
  Allows upload/download of files.
• Part 2 www (which Internet service is being
  addressed)
• Part 3 sub-domain name name of organisation
  that controls the site that the page is stored on
• Part 4 top-level domain indicates the type of
  organisation
• Part 5 the country in which the site is located

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Addressing of WWW

• Examples
• www.bbc.co.uk
• www.bto.org
• www.rspb.org.uk
• www.btinternet.com
• www.nhs.gov.uk
• www.mit.edu
• www.whitehouse.gov
• .au .de .fr .gr .no .se .ie .br .id .pk .ru

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The need for addressing

• Routing
• Name of Site
• DNS gives a name to an IP
• Easy to remember
• Commercial use
• Can use more than one name for a web server.

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A2 ICT
Module 5
14.10 Portability of Data
PART 5 The Emergence of Standardsde facto and
de jure
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Emergence of Standards

• IBM Compatible - Hardware
• MS Compatible - Software
• Object Linking and Embedding OLE
• Useful for including and editing data from one
  application in another
• Means another application can deal with the
  protocols/standards.
• Speeds up applications reduces disk space issues

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De facto

• Have been developed through commercial use
• Often developed by companies and not available
  for other companies to use
• Unpublished standards because of commercial
  interested

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De facto

• Some are not closed system standards
• Windows is a proprietary, open systems standard
• Other programmers able to take advantage and
  write programs for the many Windows OS versions.

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De jure

• Non-proprietary (no company has rights to them)
• Created to enable computer equipment suppliers to
  connect to each others equipment
• Specifications publicly available

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De jure

• Any supplier can use them
• Examples
• USB
• TCP/IP
• Telecommunications
• Internet standards
• FM/AM