Topic 8 Portability of Data

In the exam you are expected to know about:

Protocols and standards

  • Explain the need for portability of data, e.g. ease of transferring numerical, graphical and textual data between applications.

  • Describe the need of standards for interchanging numerical, graphical and textual data between different hardware and software platforms.

Communication standards

  • 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.

 

 

Portability of Data

Data are portable if they can be processed by different application to the one that generated them.  For example a table of data can be imported from a spreadsheet into a word processor, or vice versa.  Tables from a spreadsheet can be processed by a database management system.  Data from pictures can also be imported and exported between applications.  This can happen only if there are the same standards between applications.

 

Protocols

A protocol is a set of rules and standards.  In diplomatic circles there are strict protocols that need to be observed to maintain good relationships between countries.  In this country there are protocols to be observed when meeting the Queen.  You cannot be familiar to her as you are to your friends.

In the early days of computing there were a variety of standards.  In effect the languages were different, for example ASCII and EBCDIC. 

Since computers from many different manufacturers need to be connected together there need to be standard rules to enable them to communicate.  Standards have to be drawn up that cover everything from the number of pins on a connector to the menu displays for a particular application.  These standards may disallow capabilities that may be above the standard, but the advantage of being able to communicate with other machines far outweighs the local advantage of the increased performance.

Standards are divided into:

Question 1  Why do all keyboards have the QWERTY layout?  Would it be a good idea to have a new layout?  ANSWER

De facto standards arise through market dominance.  A computer that has wonderful performance, is cutting edge technology, etc. will not sell unless it is compatible with standard machines or software.  We may not like the International Business Machines corporation, of William Gates' Microsoft, but it's a fact of life that they are the market leaders and they call the shots.

Question 2  What de facto standards are there for PCs?  ANSWER

 

Protocols and the Internet

Communications between computers on the Internet is governed by the TCP/IP (Transport Control Protocol/Internet Protocol) which has become the de facto standard.  The language on the internet is HTML (Hypertext Mark-up Language).  When writing pages for the Internet, I use FrontPage that turns my word-processed text into HTML.  (I don't know that much about HTML.)  Here is the HTML coding for this last paragraph:

<p><font face="Trebuchet MS">Protocols and the Internet.</font></p>
<p><font face="Trebuchet MS">Communications between computers on the Internet is
governed by the TCP/IP (Transport Control Protocol/Internet Protocol) which has
become the de facto standard.&nbsp; The language on the internet is HTML
(Hypertext Mark-up Language).&nbsp; When writing pages for the Internet, I use
FrontPage that turns my word-processed text into HTML.&nbsp; (I don't know that
much about HTML.)&nbsp; Here is the HTML coding for this last paragraph:</font></p>
<p>&nbsp;</p>
 

Let's look at the address for a website.  It is often called the URL (Uniform Resource Locator)  Each website has a unique number, which consists of four numbers separated by full stops.  Your web browser may display it.  Numbers are not easy to remember, so the domain name system allows a more memorable address to be remembered.  Each web site has a home page, from which all the other pages may be viewed.  In complex sites (like this) you have to go through several pages or portals.  In this case you went from the home page to the contents, to ICT A2, then Module 5 to Topic 8.

This site has the address:

http://www.antonine-education.co.uk

The http:// stands of hypertext transfer protocol, used for downloading material from websites.  There are others:

Then there is the www.  This indicates that the site is on the World Wide Web part of the Internet.  Some sites are not, so the www. is missed out.

The next bit is the domain name, sometimes called the sub-domain.  It is a name thought of by the owner of the site.  I chose antonine as the last of my first names is Antony.  I could have called it jirvine, or ant09.  When initially setting up the site I looked to see if my chosen name was free.  Antonine.co.uk exists elsewhere, which is why I added the education bit.  Also there is the Antonine Wall in Scotland which came into my thoughts, and inspired the logo.

The fourth part is called the top level domain.  It states the kind of institution:

My site is a .co, which costs less than a .org domain.

The last part is the country, e.g. .uk for UK, .fr for France, or .de for Germany.

The URL is actually the address of a document, while the IP address is that of the computer.  Documents on the internet end with an extension, .htm indicating it's an HTML document, for example:

http://www.antonine-education.co.uk/antonine_education_contents.htm

Question 3  Explain what is meant by the terms:

IP (Internet Protocol) address, domain name, URL.    ANSWER

 

Communication Software

Protocols specify:

The speed of transmission is related to the bandwidth of the channel, for example an optical fibre, a wire, or a radio link.

Baseband carries one signal at a time, as 0 or 1 (off or on).  The signals can travel very fast, but can only travel short distances.  Booster equipment is needed every 300 metres.

Broadband carries multiple signals on carrier waves with the signals 0 and 1 carried as variations on the waves.

The speed at which data is sent is called the baud rate, measured in bits per second (bps).  The character consists of 7 or 8 bits with a start and stop bit.  Each character requires 10 bits, so a 56 k modem transmits about 5600 characters per second.  Telephone lines operate on analogue signals (waves) rather than digital (on or off).  Therefore a modem is needed which operates between 9600 and 56 000 bps.

A broadband modem transmits data at very much higher speeds.

Data can be transmitted one bit after another down a single channel.  This is called serial transmission.  Serial transmission can be asynchronous, where each character has a start and a stop code.  The computers do not need to be kept in step, but the speed of transmission is low.  In synchronous transmission the computers are kept in time, and the data are sent in timed sequences.  This allows much faster transmission.

In parallel transmission all the bits that make up a character with a parity bit are transmitted simultaneously.  This allows for rapid transmission of data, but requires each bit to have its own wire to travel in.  Hence parallel cables are thick.  Parallel transmission can only be done up to about 5 metres.

An example of a parallel cable is that between a computer and a printer.  Many computers are nowadays connected to peripherals by a Universal Serial Bus (USB).

 

Now try the Topic Quiz