ZARKOVIC TOOLS, Part 4Tools for Information Processes
In this lesson we will concentrate on the final two information processes: – Transmitting and receiving data – Displaying data
Transmitting and receiving data This is an important area of study as it forms the basis of the Year 12 core unit Communications It is highly theoretical and involves the explanation of a lot of technical terms
Communication Concepts There are a few basic concepts in the syllabus that need to be carefully defined and explained to students
Parallel vs Serial data transmission Parallel – the data bits are transmitted simultaneously along multiple (‘parallel’) channels – Used extensively inside the computer system e.g. data bus, address bus, etc – Quick – Can only be used over short distances(<1m) as the signals begin to decay or channels get out of sync Serial – the data bits are transmitted one after the other (in single file) along a single channel – Slower than parallel – Good for long distances e.g. networking
Parallel vs Serial data transmission Parallel Serial Transmission Transmission0 0 1 0 0 1 0 1 0 0 0 0 0 0 0 0To CPU …. To server…
Direction of data flow Can be classified as simplex, half duplex, full duplex Simplex – data flows in one direction only e.g. Free to air television Half Duplex – data can flow in both directions, but not simultaneously e.g. Walkie Talkie Full Duplex - data can flow simultaneously in both directions e.g. telephone
Synchronous vs Asynchronous Refers to the method used to transmit serial data Asynchronous – Each byte of data is sent one at a time – It is encapsulated within a ‘packet’ of 10 to 12 bits which may have 1 or 2 start bits and stop bits – A parity bit is included to aid in error checking (if used) – Most common method used outside of the computer Synchronous – A collection of data is stored as a single unit called a frame – The complete frame of data (1024 bytes or more) is transmitted to the computer – Faster, more efficient than asynchronous but expensive – Mostly restricted to use on large computer systems
Asynchronous Communication Parity bit Start bit(used for error checking) 11110111010 A single character of Stop bit data Every character of data is transmitted with the start bit, stop bit and parity bit
Synchronous Communication Groups of characters are transmitted for processing by a mainframe computer Individual Characters 11000001110111010110110000001110Frame of dataThe client and the server computer must synchronise their internalsystem clocks. When this occurs the data fame is sent as a blockto the server for processing.
Speed of transmission Speed of transmission is given as bits per second (bps) or baud A speed of 56000 bps means 56000 bits of data is transmitted per second Baud refers to the number of electrical signals used to transmit data i.e. timing intervals per second More than one data bit may be able to be transmitted per time interval Therefore, a transmission speed of 56000 baud would, in most circumstances, be considered faster than a speed of 56000 bps
Hardware Busses – these are the links used within the computer to transmit data from one part of the computer to the other The most important ones are the – Data bus – Address bus The data bus is the set of parallel links used to move data between RAM and the CPU = the ‘wider’ the bus the faster data is moved The address bus is used to send data request signals to the various memory locations in RAM The ‘width’ of the address bus is important because it determines the number of addressable memory locations (ie memory size) e.g. 16 bit address bus => 216 = 65536 (=64kb) addressable memory locations
Hardware There is also a control bus which is used to transmit control signals to various computer components As well, there are expansion buses, which enable peripheral devices to talk to the CPU, once the correct expansion card has been installed
Hardware Students need to know the general operational principles of a modem Since the standard telephone system still uses analogue signals to transmit a lot of its data, signals from the computer must be converted from digital to analogue This is done by the modem The term MODEM is derived from MOdulate / DEModulate MODulation occurs when a digital signal is converted into an analogue signal DEModulation occurs when an analogue signal is converted into a digital signal Modems can be internal (built into the system) or external Modern modems have additional capabilities e.g. used to send faxes
Hardware Networks are also a major part of the Year 12 topic Communications but it only has to touched on lightly here Students need to know the difference between a Wide Area Network (WAN) and a Local Area Network (LAN) If you want (and you have time) other network concepts can also be introduced e.g. ethernet, telecommunications
Software Basically students need to learn the following – Types of communications software Browsers FTP Telnet, etc – The role of protocols in enabling communication to occur – Electronic mail (although 99% of all students I’ve taught already know it) e.g. they need to be clear about what CC: and BCC: mean and how to add an attachment to an e-mail – Compression software (like WinZip) and what it does – Encryption of data – why is this necessary?
Social & ethicalA lot of scope in this topic to explore social and ethical issues: How do we protect against the transmission of viruses? What is netiquette and why is it important? What copyright issues relate to using the internet? How has work changed since the explosion in communications technology?
Displaying data…. Involves the output of data/information to meet the purpose for which the system was originally developed How data/information is displayed depends on the context e.g. data from a CAD program can be displayed on a screen in the engineers office, however, it can also be displayed using a computerised lathe in the workshop
Display Hardware Students need to know the basic operating principles for a number of output devices e.g. – Monitor – Printer – Speaker – Plotter Power’s book covers this fairly well, although Ware & Grover’s book does a better job outlining the operational principles of display hardware
Display Hardware At many schools the industrial arts faculty will have a plotter and they are usually quite keen to demonstrate its use to students Students should also be shown: the operation of a data projector laser printer v bubble-jet CRT v LCD v plasma screens Investigate newer display technologies e.g. interactive whiteboards, virtual reality, touch sensitive screens, etc
Display Software All application software displays data in some way An application may be able to display data in more than one way e.g. In the Access database data can be displayed as a table, using a form, as a result of a query or as a report
Non-Computer Tools E.g. a story board is diagrammatic way of showing how data files can be linked together - a very important skill as it is of particular use when developing multimedia E.g. old v new animation techniques (jargon is still the same though)
Social and Ethical Issues Inclusivity issues e.g. can computer screens can be adjusted for visually impaired users? Investigate assistive technologies available for the disabled e.g. are web designers providing suitable display alternatives for disabled users? Offensive and pornographic material on the web. Should free speech be limited? Whatever happened to the ‘paperless office’?