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HSC Information Processing and Technology/Communications

Characteristics of Communication Systems
COMMUNICATION SYSTEM- allows people to send and receive data and information. All communication systems have five basic components:
 * DATA SOURCE- produces the data to be sent.
 * TRANSMITTER- encodes the data into a single signal suitable for a transmission medium.
 * TRANSMISSION MEDIUM- is a channel, such as a cable, is which the signal is transmitted to the destination. Signal may be changed or distorted during transmission.
 * RECEIVER- decodes the signal back into the original data or an approximation of the data.
 * DESTINATION- is the receiver of the information.

Communication systems are used in information systems when participants need to transmit and receive data and information. Good communication systems have an accurate, reliable and secure transmission medium and should have a minimum delay in communicating. Good communication depends on protocols, handshaking, speed of transmission and error checking which all depends on the information technology used in the communication system.

Protocols
PROTOCOL- is a set of rules that governs the transfer of data between computers. It defines how the information is transmitted and how errors are detected. Two computers must use the same protocols when communicating otherwise the data transfer may be unsuccessful. Protocols are written into internationally accepted standards such as the OSI reference model.
 * OSI REFERENCE MODEL- divides data communications into seven layers. Each layer expresses the standard using a protocol. The bottom layers are responsible for data transfer from one place to another. They specify things such as plugs, format, method of transmission, error checking.
 * (See page table below for examples of common protocols).

Handshaking
Handshaking is used to establish a communication session for senders and receivers. It refers to a series of messages or signals used to establish whether the devices are compatible and thus able to communicate.

HANDSHAKING is an agreement about which protocol to use to accomplish the exchange of information. Data can only be successfully transferred if this occurs. It is a series of signals that flow between devices during data transmission. Handshaking is needed between devices as they may have different capabilities and may transfer data different ways. Handshaking involves sending signals to indicate the type of protocol to be used. The transmitting device will send this signal and wait for a response. When two devices successfully handshake a connection is made. If unsuccessful the devices ‘hang up’ and try again. There are two methods of handshaking to control the flow of data;

 * HARDWARE FLOW CONTROL uses a dedicated connection such as a wire. It is only practical when devices are close enough to be linked by a cable. Common hardware protocol is RTS/CTS (request to send/ clear to send).
 * SOFTWARE FLOW CONTROL uses a special code sent with the data and is used for long distance communication. Common software protocol is XON/ XOFF (X stands for transmission). When a break in transmission is required the XOFF command is sent etc.

Bandwidth
BANDWIDTH- is the capacity of the channel or transmission medium. The speed of transmission is determined by the transmitting device and the bandwidth. A transmission medium with a high bandwidth can transfer more data. The speed of data transfer is measured by the number of bits per second, or the baud rate.

Bits per Second
BITS PER SECOND (bps) or BIT RATE- is the maximum number of bits that can be transmitted in one second. This includes special bits used in asynchronous transmission and any error checking bits.

Baud Rate
BAUD RATE is the maximum number of data symbols or electrical signals that can be transmitted in one second. Because one data symbol may contain more than one bit the baud rate and bit rate may not be the same.

Error Checking Methods
Received data may contain errors caused by interference in the signal or by errors in encoding and decoding the data. Errors must be detected then corrected. Methods include:

Parity
PARITY CHECKING is a method of checking for errors in data transmission using an additional bit called a parity bit. This bit is used only for the purpose of identifying if the bits being moved have arrived successfully. The sender and receiver decide whether to send using an odd or even parity bit. For example, with 8 bit ASCII:
 * 10011010 0 (even parity, 9th parity bit must be 0 to keep it even)
 * 11001001 1(odd parity, 9th bit must be a 1 to make it odd)

Checksum
CHECKSUM is a method of checking for in data transmission by counting the total number of bits in a data packet. A data packet is created by dividing the total data into smaller groups called packets. The count of bits in a data packet is attached to the data packet. It is used by the receiver to check whether all the bits have arrived successfully. If the count matches it is assumed that a complete transmission was successful.

Cyclic Redundancy Check (CRC)
CYCLIC REDUNDANCY CHECK (CRC) is a method of checking for errors in data transmission using a division process. The data is divided into predetermined lengths by a fixed divisor. The remainder of the calculation is attached and sent with the data. When the data is received, the remainder is recalculated. If the remainders do not match, an error in transmission has occurred.

Dealing with Errors
The receiver may drop the packet, such as in IP, they may only acknowledge correct packets as occurs in TCP, or they may request that packets containing errors be resent, as occurs with Ethernet.

Communication Settings
PARAMETER is a variable that is given a constant value for a particular application. Communication settings can be changed by the user to ensure a connection between two devices. These settings are often a parameter. Some common parameters include bps, data bits, parity, stop/ start bits, and flow control:

BITS PER SECOND is the speed of transmission

DATA BITS are the number of bits in each group of data. Each group is usually sent as a byte such as 7-bit or 8-bit ASCII.

PARITY is whether the data contains a parity bit for error detection. Parity is odd, even or none.

STOP/ START BITS are the number of stop and start bits used in asynchronous transmission. This parameter is used to identify each byte. The normal range is between 0 and 2 while some systems only use a stop bit.

FLOW CONTROL is the software handshaking protocol.

Teleconferencing
TELECONFERENCING is the use of an electronic transmission to allow a meeting to occur at the same time in different locations. It is an alternative to face-to-face meetings. Teleconferencing uses audio and video communication to go beyond the normal telephone call.

Advantages: Business people such as the managers at head office and at branch office can conduct formal meetings at scheduled time without the need to travel over large distances. As a result, the cost to travel is reduced. Additionally, teleconferencing systems allows decisions to be made faster, and also it allows employees of organisation to interact with one another. Hence, new innovative ideas emerge during the conference.

Disadvantages: Users will not be able to see each other face to face and as result there will be little recognition of the nature and personality of other people with whom the users work with. Additionally, there will be no social relationship between people.

Audio Conferencing
AUDIO CONFERENCE- is a single telephone call involving three or more people at different locations. It is a service provided by a telephone company where audio data is transmitted and received using existing phone lines.

Video Conferencing
VIDEO CONFERENCE- is a meeting that allows people in different locations to see video images if each other on a screen, as well as hear speech. Video conferencing requires a high bandwidth. Video conferencing simulates face-to-face meetings and reduces costs on not buying airfares, accommodation and meals, and saves time and energy involved in travelling. Teleconferencing is frequently used in business and distance education. However it does remove the inter-personal relationship of face-to-face meetings.

Messaging Systems
MESSAGING SYSTEMS- are used to send messages to people in different locations who may receive the message at a later time. Messaging systems involve the creation, storage, exchange and management of messages, which are sent to an individual, or a group of people. The oldest form of messaging system is letters while tradition systems include the telephone and fax:

 * TELEPHONE- is a system for transmitting sounds or speech along telephone lines to distant locations. It is a convenient method of communicating with people around the world. A telephone answering machine is a communication system as it stores messages for hearing at a later time.
 * FAX (OR FACSIMILE) MACHINE- is a system of transmitting and reproducing documents by means of signals sent over telephone lines. The fax machine scans a document and converts it into a bit-mapped image, which is compressed and sent over the telephone network to a destination fax machine. This destination machine decompresses the image and reconstructs the original document. Fax machines have become popular as people can quickly transfer a hard copy off a document or send a written message. Computers equipped with a fax modem can perform the same tasks.

Voice Mail
VOICE-MAIL (V-MAIL)- allows communication with other people by storing and forwarding spoken messages. The sender dials a voice-mail number and records a message, which is digitally stored on a computer system and can only be retrieved by the intended receiver. To retrieve the message this person dials the voice-mail number using any phone, enters an account number and password. Once in they can delete, save or forward the message to another person. Voice mail combines the features of a telephone answering machine and some of the concepts of email. It provides some advantages over email as more people have access to a phone than a computer, and people often express feelings better with the spoken word. However email is better for sending complex information and different data types.

Electronic Mail
ELECTRONIC MAIL (EMAIL)- allows communication with other email users by sending and receiving electronic messages using a computer. Email was one of the earliest uses of the Internet. It is a fast, economical and convenient method of sending messages all over the world in minutes. To use email you need a computer that is linked to a network or the Internet, an account with an Internet service provider (ISP), an email address and email software.

EMAIL ADDRESS- anyone with an email address can receive email and email can be written to anyone that has one. Email addresses are unique and obtained free. They consist of two parts separated by @ symbol in the form ‘name’@’domain name’. The first part is the name of the account. The second is the domain name, which is the location of the account on the Internet. It identifies the specific computer or server where the person's email messages are stored.

EMAIL MESSAGES contain two main parts, the header and body of the message:

 * HEADER- is similar to an envelope as it contains information needed to deliver the message. The sender'’ email address is usually automatically inserted. The header contains four main parts that the sender fills in:
 * EMAIL ADDRESS (To:) is the address of the person receiving the message, which must be correctly typed.
 * CARBON COPY (Cc:) sends the same message to other people apart from the main recipient (optional).
 * BLIND CARBON COPY (Bcc:) sends a copy to other people without revealing that these other people got the message (optional).
 * SUBJECT is the topic of the message or a brief description (optional).
 * BODY- of the message is typed using the email software or imported or copied from a word processor. The user does not have to be online to compose. Messages can be written offline and sent when the user logs on to the network or Internet. This saves ISP on charges. Email messages are often short and typed quickly. Some people use inventive spelling. When email is sent it is stored on the server where the receiver’s account is until the person checks their email. After the email is read, it can be deleted, printed or stored in an appropriate folder for later reference. The user can also:
 * REPLY to the email message by clicking the ‘reply’ icon. The address of the original sender and the subject are automatically inserted in to the header of the reply. Leaving the subject the same identifies the ‘thread’ of the message.
 * QUOTING is retaining the previous message in the reply so that the original sender remembers the message.
 * FORWARDING is sending a message already received to someone else.

Email software also provides a number of features to help create email:

ADDRESS BOOK- is used to store email addresses. This saves time typing the address and avoids having to remember each one.

MAILING LIST- is a group of people who may want to receive the same messages e.g. people working on the same project or with the same interests. Mailing lists are created by entering each address of each person in the list and giving it a name.

SIGNATURE- is several lines automatically appended to outgoing email messages and may include an email address, Web site, graphic, occupation or phone number.

Electronic Commerce
ELECTRONIC COMMERCE (E-COMMERCE) is the buying and selling of goods and services via the Internet. It has become a multi-billion dollar source of revenue for the world'’ businesses. It provides 24-hour availability, global reach, the ability to interact and provide customer information, and a multimedia environment. E-commerce is expected to expand into retail areas as each day there are businesses being established which rely entirely on Web sales.

Electronic Funds Transfer (EFT)
EFTPOS (electronic funds transfer at point-of-sale) is a system that allows people to purchase goods and services using a credit or debit card. It is the electronic transfer of money from the customer's bank account to the retailer's. It has made shopping easier for customers and allows retailers immediate payment if the connection is made and approved. Each point-of-sale terminal is linked to the computer of the customer's bank using the account number on the card. Entering the PIN number is a security measure to identify the customer.

ELECTRONIC BANKING allows customers to view their account balances and transaction histories, transfer money between accounts and pay bills using Bpay. It provides services 24 hours a day but cannot counter for cash or cheque withdrawals. However automatic electronic debits are replacing cheques, which are expensive and ineffective as they pass through many hands before the transaction is completed. Some electronic banks require people to download special banking software and install it. Electronic banking raises the issue of security yet all banks are determined to make their online services safe from interference and to secure customer details using data encryption to secure data transfer between the two involved computers.

Methods of Data Transmission
DATA TRANSMISSION occurs in two ways:

Parallel Transmission
PARALLEL TRANSMISSION is the transmission of data simultaneously using separate channels.

Serial Transmission
SERIAL TRANSMISSION is the transmission of data one after the other. It is used to transmit data to peripheral devices, and is used on networks. Serial transmission can be either synchronous or asynchronous:

Synchronous and Asynchronous Transmission

 * ASYNCHRONOUS TRANSMISSION is the sending of data by identifying each byte with special start and stop bits. It has become the standard for personal computers.
 * SYNCHRONOUS TRANSMISSION requires all the data to be sent at the same rate (the same number of bytes is sent each second). This is synchronised by each device using a clock. Synchronous is faster and more efficient than asynchronous as there are no extra bits. It is used on larger computer systems.

Modes of Data Transmission
DIRECTION OF DATA- can be simplex, half-duplex or full-duplex mode:

 * SIMPLEX MODE allows transmission in one direction only from the sender to the receiver e.g. radio.
 * HALF-DUPLEX MODE allows transmission in both directions but not at the same time. The sender and receiver take turns e.g. walkie-talkie.
 * FULL-DUPLEX allows transmission in both directions at the same time e.g. email. Most communication systems use this mode.

Networks
NETWORK- is a number of computers and their peripheral devices connected together in some way. Each device in a network is called a node. Terminals are any devices that send data to and receive data from another computer system. If a terminal has both memory and processing capabilities it is called an intelligent terminal. Most personal computers are classified this way and called workstations on a network. The simplest form of a network is when two computers are connected directly to each other via a cable yet networks can involve thousands of computers. Networks are classified as LANs or WANs:

LANs
LOCAL AREA NETWORKS (LANs) connect computers within a building or group of buildings on one site. LANs cover a small geographical area and the computers are linked by coaxial cable or fibre-optic cable. There are three main advantages in using a LAN:
 * sharing limited hardware resources such as printers, hard disks and modems.
 * sharing application software such as word processors and DBMSs.
 * improved communication among uses by sending electronic messages.

WANs
WIDE AREA NETWORKS (WANs) connect computers over hundreds or thousands of kilometres. WANs often consist of a mainframe computer called the host and a number of terminals e.g. EFTPOS and ATM terminals. A WAN may use a private lased line, the normal phone network, or a combination of both:
 * PRIVATE LEASED LINE- is dedicated to the network. It offers higher transmission speeds than the PSTN.
 * PUBLIC SWITCHED TELEPHONE NETWORK (PSTN) are relatively cheap if computers do not require a constant connection however they are not guaranteed and can be interrupted.

Packet Switching
PACKET SWITCHING is a technique that divides messages into small data packets, transmits these packets, and later joins them to form the original message. It is used to send most data over networks and the Internet. It allows multiple users to use the same transmission line by interspersing the data packets from different users. Data packets may not be sent over the same path and could arrive at the destination at different times and in the wrong order. Each packet contains an address and control instruction to reassemble the message in the correct order.

Network Topologies
NETWORK TOPOLOGY is the physical arrangement of the devices in a network. Types include:

 * STAR TOPOLOGY- has a central computer WITH EACH DEVICE CONNECTED DIRECTLY TO IT. The central computer serves as a switch. It receives messages and sends them to the destination device. This topology requires extra cabling as each device is connected to the central computer rather than the next device. If one cable is broken the network can still operate. Yet if the central computer fails, the whole network fails. It is also limited by the processing power of the central computer. Star networks use a time sharing device that allocates a certain amount of CPU time to each user. It is the most common topology for a mainframe.
 * BUS TOPOLOGY- is an arrangement where all devices are connected to a direct line called a bus. Each device has a unique identity and can only recognise the signals intended for it. Devices check the bus and retrieve their messages as data travels along the bus. Each device is considered to be connected to every other device and can communicate directly along the bus to any other device. Bus topology is one of the easiest to set up and can still operate if one node fails. It is used by Ethernet and PowerTalk.
 * RING TOPOLOGY-is an arrangement where all devices are attached so that the path is in the shape of a continuous circle. Each device in the ring has a unique address. Data flows in one direction, moving from device to device until arriving at its destination. Token ring is the most common form of access for a ring topology.

Network Access Methods
NETWORK ACCESS METHODS for dealings with multiple users wanting to access the network at the same time include:

 * ETHERNET- the first industry-standard LAN access method, or protocol, based on a bus topology. It is defined in a standard called IEEE 802.3. Ethernet allows data to be transmitted simultaneously to all nodes on the network in both directions. Addressing information allows each node to recognise and receive individual data packets intended for it. With these packets travelling simultaneously collisions will occur and cause errors. To overcome this Ethernet uses (CSMA/CD).
 * CARRIER SENSE MULTIPLE ACCESS AND COLLISION DETECTION (CSMA/CD)- all nodes have the ability to sense signals on the network. When a node wishes to transmit it ‘listens’ to the bus for signals. When there is no signals it transmits. A collision may occur if two nodes sense a clear bus at the same time. When a collision is detected each device stops transmitting and retransmits at a later time.
 * TOKEN RING- a LAN access method, or protocol, based on a ring topology. The token ring operates by continually passing special data packets called tokens between nodes on the network. Workstations with data to send capture a free token and attach data along with addressing information. A busy token with data cannot be used by other nodes. When the data arrives at the destination, it is replaced with an acknowledgment and sent back to the original sending node.

Network Hardware
NETWORK HARDWARE- special purpose hardware devices are needed to successfully construct a network.

Network Interface Cards
NETWORK INTERFACE CARD (NIC)- is required by every computer connected to a network. An NIC is an expansion card that fits into an expansion slot on a computer or other device so that it can be connected to the network. Most NICs require a network cable connection and have connectors on the card for different cable types. The type of NIC depends on the type of network. NICs package data according to the rules of the network operating system.

Servers
SERVER- is a computer that provides services to other computers on the network. Individual computers log on to the server, which gives them access to files, applications or peripheral devices. Types include:
 * FILE SERVER- is a controlling computer in a network that stores the programs and data shared by users. These can be retrieved by any node that has access rights.
 * PRINT SERVER- is a computer in a network that controls one or more printers and stores data to be printed. It can be used with or without a file server.
 * MAIL SERVER- is a computer in a network that provides email facilities. It stores incoming mail for distribution to users and forwards outgoing mail to appropriate devices.
 * WEB SERVER is a computer in a network that provides a connection to the Internet. All Net traffic is directed through it.

Linking Hardware
Devices used to determine the path between networks include:

 * ROUTER- a device that determines where to send data packets between at least two networks. Its decision is based upon its current understanding of the networks. A router maintains a table of the available routes and their conditions. It uses this together with distance and cost algorithms to determine the best route for a given data packet. Data packets often travel through a number of network and routers before arriving at their destination.
 * SWITCH- a device that directs data packets along a path. May include the function f a router although switches are a faster and simpler mechanism, as they don't maintain a knowledge of the networks. A switch is not always required as many LANs are organised so each node inspects each data packet.

The actual interconnection between networks is achieved using a:

 * BRIDGE- a combination of hardware and software to link to similar networks. Often connects LANs that use the same protocol such as Ethernet. A bridge examines each data packet on a LAN and forwards any data packets addressed to a connected LAN. Bridges are faster than routers because they connect networks using the same protocol.
 * GATEWAY- a combination of hardware and software to link two different types of networks. This usually involves converting different protocols.

REPEATER- is used to rebuild a fading signal (caused by long distances or electromagnetic field interference) to its original strength and shape before transmitting it onwards. It ensures data is received as it was sent. A network repeater is used in a LAN to connect network segments. They are less intelligent than a bridge or gateway.

HUB- is a central connecting device in a network. Data arrives at the hub from one or more devices and is forwarded out using just one cable. A hub can include a router. Most were originally passive (data simply passed through without change). Intelligent hubs are more frequently used today. These contain a CPU and network operating system, which allows them to perform some server functions.

Transmission Media

 * WIRE TRANSMISSION transfers the data through wires and cables, which must be, protected from damage, take up space and can be difficult to install. However wire transmission can carry large amounts of data with little interference from other signals. Two types of transmission are used. Baseband networks use the entire capacity of the cable to transmit only one signal at a time. Broadband networks divide the cable so that several signals can be transmitted at once. Types include:
 * TWISTED-PAIR consists of two thin copper wires twisted to form a spiral. This reduces the amount of interference from other cabling. Two main types are unshielded twisted-pair (UTP) which is the most common and shielded twisted-pair, which is used, in ‘noisy’ environments where its shield protects from excessive electromagnetic interference. Twisted-pair is slowest medium with a bandwidth up to 60kbit/s.
 * COAXIAL CABLE consists of a single copper wire surrounded by an insulator, grounded shielding and an outer insulator. Shielding allows data to be transmitted with little distortion. Commonly used over distances less than a few kilometres. Bandwidth is 10Mbit/s.
 * FIBRE-OPTIC CABLE uses a small laser of light to carry data in small glass fibres free from electromagnetic interference, securely and at high speeds without errors. These are replacing conventional copper-wire cables. Bandwidth is in excess of 400Mbit/s where a single strand can carry thousands of phone conversations. However it is expensive.
 * WIRELESS TRANSMISSION moves the data through air and space without the need for a fixed physical connection between source and destination e.g. radio. Wireless LANs use radio waves, not cables. Wireless LANs are not popular due to problems in maintaining signal quality and concerns about electromagnetic radiation. Wireless transmission involves:
 * MICROWAVE is a high frequency radio signal sent through space in a straight line from one antenna to another. Antennas are placed on tall buildings or mountaintops to continue transmission over long distances. Microwave is faster than phone lines or coaxial and even though it is reasonably error free, weather conditions and objects can obstruct the signal and affect transmission.
 * SATELLITE. These are specialised transmitters and receivers that are launched by a rocket and placed in orbit around earth. A signal is sent from one ground station to the satellite, which receives and retransmits it to another ground station. Each ground station uses a satellite dish to send and receive. Satellites can transmits large amounts of data over long distances at great speeds. There are hundreds currently operating and used for weather forecasting, television broadcasting, and radio and Internet communications.
 * MOBILE PHONES transmit data to a grid of cellular stations, which are linked to the wireless transmission telephone network. Mobiles use radio waves to communicate with the cellular station. They are a portable device, yet monthly fees are higher than those for a normal phone in most countries.

Network Software
NETWORK SOFTWARE must be installed on each computer in a network. This software contains the ‘rules’ for communication and determines how the network devices send and receive data. Network software is organised by a network administrator.

The Role of the Network Administrator
NETWORK ADMINISTRATOR- is a person who manages a network within an organisation. Their responsibilities include network security, installing new applications, distributing software upgrades, monitoring daily activity, enforcing licensing agreements, developing a storage system and providing routine backups. These are completed using the network operating system.

NETWORK OPERATING SYSTEM (NOS)- is an operating system that is designed primarily to support computers connected to a LAN. Examples include Microsoft's Windows NT and Novell's Netware. One part of the NOS resides in each node and another resides in the server. It controls the flow of data between the network devices and requests for data, organises messages from nodes until the network is ready to process each message. Tasks include:

 * ADMINISTRATION- adds, removes and organises users, installs hardware devices and software applications, and carries out maintenance operations such as backup.
 * FILE MANAGEMENT- gives users access to remote hard disks on the server and provides a file system and the ability to manage a network directory.
 * APPLICATIONS- handles requests from users to share data and applications.
 * RESOURCE MANAGEMENT- allows network devices to be shared, assigns users to printers, and orders print jobs.
 * SECURITY- monitors and restricts access to network resources.

LOGON is the procedure used to gain access to the network. The user is identified by a user ID and password. The ID usually conforms to a limited length and the password often must contain one digit. The password is a security measure and must not be readily available or easily guessed and must be kept secure. The password file should be encrypted and protected from unauthorised access. Network systems may require users to frequently change passwords as a security measure. The logon procedure usually allows the user two or three attempts to enter the correct ID and password. Mistakes can occur in typing or the communication link. After logging on the user is given access to only those features authorised by the network administrator. The correct logoff procedure should always be carried out to clear the communication line for another user.

The Internet, Intranets and Extranets
INTRANET- is a private network that uses a similar interface to the Web. It usually has a connection to the Internet and consists of many interlinked LANs. The main purpose of an intranet is to share information (e.g. staff news, policies) and computing resources among the employees of and organisation. When access to the Net is provided it is through firewalls.

FIREWALL- monitors the flow of data in both directions to maintain the security of the organisation.

EXTRANET- is an intranet that is accessible to customers, suppliers or others outside the organisation. Provides such information as product descriptions, answers to frequently asked questions, warranties and how to contact customer service.

Collecting
COLLECTING data for a communication system involves generating the data to be transmitted. Collecting data involves a range of collection devices to gather different types of data. The choice of device depends on the application and the type of data to be transmitted. Some devices include:
 * ATM terminals for electronic banking
 * EFTPOS terminals for a retail store
 * telephones for voice mail
 * keyboards for email
 * video cameras for a surveillance system.

Processing
PROCESSING of data in a communication system is the manipulation of the data. After collection the data must be converted into a form for transmission. This involves encoding and decoding: • ENCODING involves converting data from its original form into another form for transmission. • DECODING converts the data from the form used for transmission back into its original form.

The type of encoding or decoding depends on whether the original data is in analog or digital form:

• ANALOG DATA is represented by using continuous variable physical quantities such as voltages. Most natural events in the real world are therefore in analog form. Sounds, images and video are in analog form. Analog signals are pulses, usually electrical or optical, in the form of a continuous wave.

• DIGITAL DATA is represented in the form of digits or numbers. IT works with data in digital form. Digital signals are represented using a series of 0s and 1s.

Encoding and Decoding Methods
The form of the data and the transmission signal affect the quality of the data received and the cost of transmission. The quality of analog data depends on maintaining the exact wave as it moves through wire or space. It is corrupted there is no way of regenerating the wave. It is possible to regenerate digital data because it only involves distinguishing between a 0 and a 1. There are four encoding and decoding possibilities in transmission:

 * ANALOG DATA TO ANALOG SIGNAL. The wave shape of the data is encoded into the signal e.g. a telephone.
 * DIGITAL DATA TO ANALOG SIGNAL. A series of 0s and 1s is encoded into a continuous wave e.g. a modem modulates (encodes) digital data from a computer into analog signals for a phone line. When this is received by another modem it demodulates (decodes) it back to digital data.
 * DIGITAL DATA TO DIGITAL SIGNAL. A series of 0s and 1s is transmitted by sending it through a channel as a series of on and off pulses e.g. a LAN where the computer or a peripheral devices encodes the data. Low error rate.
 * ANALOG DATA TO DIGITAL SIGNAL. The wave shape of the data is encoded into a series of 0sand 1s e.g. TV. This is called digitising. Images are digitised by scanners using a process called sampling.

Client-Server Arhitecture
CLIENT-SERVER ARCHITECTURE describes the software relationships between the client (user) and the server. A client sends a request to the server according to an agreed protocol and the server responds. It provides a convenient way to interconnect programs that are distributed across different locations in a network. Most business applications and the Internet use client-server architecture. The Web browser is a client program that requests services from a Web server to complete the request.

Displaying
DISPLAYING is the presentation of information in the form of text, images, audio, video or numbers. A range of software and hardware combinations are used including:

 * TELEPHONE- displays audio information. A phone contains a transmitter that converts sound into a signal suitable for the transmission medium and a receiver to convert it back to sound. A phone also displays voice mail messages.
 * EFTPOS TERMINAL- displays information about EFTPOS transactions. The terminal contains a screen to display the name and price of the product being purchased. When the customer's bank is contacted the terminal displays the approval is funds are available. It then provides a receipt.

Issues Related to Messaging Systems
MESSAGING SYSTEMS have improved communication but raised issues:

 * SOCIAL CONTEXT. Ideas delivered by messaging systems appear less forceful and caring than those delivered personally. MSs have difficulty when communication depends on expression of feelings.
 * DANGER OF MISINTERPRETATION. Communication often depends on the context inflection on a person's voice and body language. Misinterpretation can occur with email, or phone etc.
 * POWER RELATIONSHIPS. MSs may change the relationship between people in an organisation. The normal communication through middle management is affected.
 * PRIVACY AND CONFIDENTIALITY. A characteristic of MSs is that the messages are stored (e.g. email messages are stored on servers and can be accessed by the service providers) therefore there is no guarantee of privacy and confidentiality.
 * ELECTRONIC JUNK MAIL. Unwanted mail is a problem for MSs. People can send a message to one or thousands of people (spamming) very easily. If a person receives hundreds per day it wastes time and prohibiting this practice would be difficult and compromise free society.
 * INFORMATION OVERLOAD. This term refers to the enormous amount of information that people have to absorb. MSs are a source of information. The large amount of email received by some people has increased their workload and stress levels. There is often an expectation that people will reply quickly to an email than to a letter written down by someone else.

Issues Related to the Internet
INTERNET TRADING or e-commerce, is increasing at a staggering rate to meet the needs of consumers. The Net provides significant advantages for consumers such as more information about products and services, global shopping and increased competition resulting in lower prices. Some implications include:

 * TAXATION. Present governments have been unable to tax Internet transactions. This increased Net business will reduce the money governments receive from their goods and services.
 * EMPLOYMENT RAMIFICATIONS. The increase in Net trading requires more people to be employed in the IT industry and may result in fewer shop fronts and people required to run them.
 * NATURE OF BUSINESS. Traditional businesses that provide interaction opportunities are being challenged. People can complete some of their business at home without travelling.
 * TRADE BARRIERS. The developments in communication technology have made trade barriers irrelevant. The issue of where one country ends and another begins is open to question. People are buying and selling on the Net with little thought given to such issues.

CENSORSHIP is one of the most controversial issues to have arisen with the Net as it provides access to a large amount of offensive material especially to children. Some believe offensive material should be banned while others believe this would compromise free society. There have been unsuccessful attempts to censor material on the Net by governments and law enforcement bodies worldwide. The Internet Industry Association (IIA) represents Australian ISPs. It has released a code that deals with censorship of online content. The code requires ISPs to remove offensive content from their servers and to block access to classified material on overseas sites. The federal government has passed a law requiring ISPs to subscribe to this code. The difficulty with enforcing censorship is the enormous number of Web sites and the thousands of new ones published daily. Monitoring on a global basis is impossible. Clearly a multinational agreement is necessary however this would be difficult to obtain and regulate. The prime responsibility of preventing children from offensive material lies with the parents and carers.

The Internet now provides radio and video:

RADIO is being broadcasted by Web sites from around the world. These stations cater for a range of tastes.

VIDEO is also being provided online. It is replacing videotapes and other media. It allows organisations to create unlimited video channels, which are used for sales, training, communication and other purposes. Video on the Net saves time, reduces costs and provides global ability viewing. The size and quality of the video is currently less than TV broadcast but will improve with advances in technology and increased bandwidth.

Issues Related to Electronic Banking
INTERNET BANKING has raised issues:

 * SECURITY. All banks are determined to make their online services secure from interference and customer details secure. Data encryption is used to secure data transfer between computers.
 * CHANGING NATURE OF WORK. People working for the bank do not carry out the services for the online bank. Banks require more people with IT skills and fewer with banking skills.
 * BRANCH CLOSURES AND JOB LOSSES. With many people using Net banking, ATMs and EFTPOS there is less need to access the facilities provided by a branch resulting in closures and job losses.

Working from Home
TELECOMMUTING is working from home and electronically communicating with the office. It is expected to increase. Factors that will affect this include availability of bandwidth, the perceived value of telecommuting, and the opportunities to work collaboratively across distances. The Internet has allowed a new type of organisation to develop whose employees work almost entirely through telecommunication with an occasional face-to-face meeting. The main advantages of telecommuting include a greater flexibility in work hours, saving money on food, transport and clothing, and saving time. It also benefits people who are physically impaired or required to look after children. The employer saves time on overheads such as office space and furniture. Disadvantages include a lack or missing of social and professional contact offered by an external workplace, loneliness and isolation. Telecommuting can also blur the line between work and home life. The home is no longer a place where the pressures of work can be forgotten and work may be interrupted by domestic chores.

Virtual Organisations
A virtual organisation or company is one whose members are geographically apart, usually working by computer e-mail and groupware while appearing to others to be a single, unified organization with a real physical location. Groupware refers to programs that help people work together collectively while located remotely from each other.

Virtual organisations are organisations structured around the communication system. The components of an organisation are linked using information technology rather than by a defined space such as an office.


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The Computer Revolution/Computer Graphics/Corel Draw

Corel Draw is vector design software with bitmap capabilities that enforce Corel Draw to be a design software that encompasses all the necessary tools to print and publish graphic media. However, since every graphic software specializes in something and has got a user feature that is unique to uses Corel's features are the following:

 * 1) Imposition options for Printing,
 * 2) Detailed plate separation options for hexachrome plates and smart plates.
 * 3) Easy Learning curve, this is evident as print shops like the franchise Minuteman Press use Corel because it is user-friendly for owners to edit and change files as well.
 * 4) If you optimize the keyboard shortcuts then the speed of designing doubles itself.

There are many more advantages in comparison to other software such as Adobe InDesign, Adobe Illustrator, Quark Express, Etc.

Corel Draw does have some cons for example

 * 1) Duotone separation is faulty.
 * 2) Lens effects cause postscript errors.
 * 3) Bitmap effects are prone to errors and Corel crashing rituals.
 * 4) Moreover Corel Draw does not have the biggest Market share in design software. By far Adobe does. Adobe InDesign.
 * 5) Corel Draw is not also effective for web-site development and files are erroneous being publishing to HTML files.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


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User talk:69.40.115.30

Please stop adding nonsense to Wikibooks. It is considered vandalism. If you would like to experiment, use the sandbox. Thank you. Brian Brondel 03:52, 8 November 2006 (UTC)

title: User talk:69.40.115.30


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HSC Information Processing and Technology/Multimedia Systems

Multimedia Systems will probably be the easiest and most intuitive part of any IPT exam, because while you may have never know any thing about the system development cycle and the seven information processes before you began IPT, you would have known what resolution was, and what a bitmap was, etcetera.

Characteristics of a Multimedia System
Multimedia means the use of different media to present a message or to entertain. Multimedia systems are information systems that combine a variety of different media types. In computer terms, Multimedia applies to software that can different forms of information and it has only become a possibility due to development of powerful and inexpensive computers that have the ability to record and play sound, display millions of colours and record and playback video.

Text, Hypertext and Numbers
Text is any sequence of symbols that have meaning such as keyboard symbols and in multimedia text allows the users to read and review the information at their own speed.

Hypertext is text presented in such a way that when selected it links to new information. Hypertext makes multimedia interactive as it allows the user to obtain new information in any direct order which doesn’t have to be linear. Numbers, like text, are used to display information and often used for exact, accurate information.

Fonts
This is the style of which text appears. It defines the appearance of text through size, thickness, style and format.

Hypertext
Text that contains links to other sections of a multimedia program

Audio
Sound is digitised by measuring its pitch and volume thus audio can either be in waveform or MIDI (Musical Instrument Digital Interface) format which uses a digital version of sounds to create music.

Storage in MP3 Format
lossy format

Images
an image is the fundamental part of multimedia presentation as they contain a wide range of graphical information like graphs, drawings, pictures, icons etc. The hypertext images when used to provide navigation links, images are classified as hypermedia which is any display object that links to new information. An animation is a moving graphic like video and the basic principle of animation (on movie screens, TV and VDUs) is the persistence of vision.

Bitmapped Graphics
Bit-mapped graphics treat each pixel on the screen individually and represents this by bits in memory. They produce good quality images where shading and detail are needed. However, when transformed (resized or stretched), bit-mapped graphics become ragged and suffer loss of resolution. Enlarging each pixel in a bit-mapped image graphic creates staircase pattern called aliasing. Bit-mapped images require large amounts of storage. They are often stored in compressed formats, such as GIF and JPEG.

Vector Graphics
Vector graphics are made up of objects, such as a straight line, a curve or a shape. Each object is defined by its characteristics, such as position, line width, and pattern. These characteristics are stored as mathematical expressions and displayed on the screen as pixels. Some common formats include CGM, EPS and WMF.

Video
Video – or moving images are similar to animation. Both video and animation add enormous appeal to a multimedia system. Video and animation are complex data types for information systems to handle since huge amounts of data needs to move between storage devices (both primary and secondary) and the display device fast enough to create smooth motion effects. Often data must be processed before it can be displayed.

Print and Multimedia
The differences between print and multimedia including:

Modes of Display
Different modes of display – print (static) media is limited to hard copy such as books, newspapers, magazines and posters. However multimedia (dynamic media) can be implemented for computer use, wireless pocket PCs, PC/TV combination and other diverse applications. Once a book is published it cannot change thus its static but multimedia can be updated and distributed easily. In static media, changes have to be reprinted which is time-consuming, only one user can view it at one time, it can’t have sound and requires some imagination. Multimedia however has many advantages as its dynamic, changes can be immediately updated and put on website, allows multiple views at same time, has sound and interactive animations, is interactive through hypertext and hypermedia, but requires hardware and software. Print is limited to hardcopy mode while multimedia has multiple modes and print is presented in a linear or sequential way but multimedia is presented in non-linear and hierarchical way.

Interactivity
Interactivity and involvement of participants in multimedia systems – the interactive nature of multimedia is another difference from static media. Interactivity means that the user is able to make an immediate response to what is happening and modify the process. Effectively, there is a dialogue between the user and the computer or communications device and the data access and transfer can be non-linear.

The Demands Placed on Hardware by Multimedia Systems
the audio and video/animation component of a multimedia require the greatest amount of storage space and processing. Thus a high level CPU is required plus high resolution (at least 1024 x 768) for multimedia applications. Text, numbers and hypertext is usually stored as ASCII or ANSI codes as they need little space and processing.

Primary and Secondary Storage

 * Bit depth and the representation of colour data – the bit depth describes the number of data bits needed to store each pixel in an image. This sets the number of possible colours for each pixel. The bit depth controls the number of possible colours for each pixel. A display system with a bit depth of 1 could only store a 0 or a 1 for each pixel. If 1 represented white and 0 represented black, then every pixel on the screen would be either black or white. With a bit depth of 24, the colours that could be displayed are 16777216, thus a higher bit depth of 24 (true colour) represents true colour data.
 * Sampling rates for audio data – sound and other analog data is generally represented as transverse wave and converted to digital form by a process called sampling. The sampling size is the number of bits used to store each sample from the analog wave. A higher sample size results in increased accuracy but higher data storage requirements. The sampling rate is the number of samples or slices taken of the analog wave in a second. The higher the sampling rate, the better the representation of the initial analog signal.

Processing Demands

 * Video data and frame rates – processing video files requires special hardware and software to enable it to be recorded and played back. Piped video is the simplest method of displaying video footage on computer screen. A frame is a single image in a video or sequence and frame rate is the speed with which video frames are displayed on the screen. Video is shown at a certain speed so that observer’s perception of movement is one of smooth motion. The PAL (phase alternate line) displays a frame rate of 25 frames per second and current PCs cannot sustain a transfer rate between primary and secondary storage of 1,500 Mb per minute, thus compression, decreased colour depth and decreased resolution are used to process video data. Digital video editing software allows digital video to be manipulated either by an insertion or deletion of a scene and can be stored on digital media like hard disk drive, CD, DVD or tape.
 * Image processing, including morphing - when an image undergoes a process of metamorphosis and changes slowly from on image to a completely different one is called morphing where image is changed pixel by pixel. Warping or distorting is another animation technique where an image is gradually distorted by changing its pixels either by stretching or resizing so image results in a different form e.g. Changing your picture so you have very large ears. Image processing is an aspect of video work that demands processing power and morphing and warping are the primary types.
 * Animation processing – is the process of displaying a series of drawn images in quick succession, creating the effect of movement. Each drawing is a frame. Animation is based on the principle of persistence of vision thus animation seeks to create an illusion of smooth movement. Computers have made the task of animation easier via 2 methods: Cel-based animation is an animation technique where each individual frame is stored separately into a memory page and creates a separate picture for each frame with only small changes between the frames. This type of animation gives the animator complete control over every frame in the animation but is time and space consuming. Path-based animation is an animation technique in which the only part of the frame that changes is the moving object. The animator describes the path or movement of every object and the system then creates the animation frames with each object drawn in its correct position. The generation of scenes in-between by path-based animations is called tweening as the animator only defines the starting and end point and the path to be taken, so tweening occurs. Thus path-based relies on system to create animations much faster with less storage required, but the animator doesn’t have much control.

Display demands

 * Pixels and resolution – a pixel is a single picture element which is the smallest controllable element on a graphics screen. A typical home VDU PC contains more than 600,000 pixels and each individual pixel’s colour and brightness is set by the computer to create an image that is displayed. The resolution is a measure of the quality or detail present in a displayed image. It’s usually described as the number of pixels across and down the screen (e.g. 640 x 480 was considered HIRES (high resolution before but is now LORES with 1200 x 860 now considered HIRES). High and low resolution describes graphic images and graphic display systems. The more pixels that can be displayed by a screen, the better the image quality or resolution.

Expertise
a number of different skills are required for the development of a good quality multimedia application such as –
 * Content providers – are people who provide material such as video footage, audio tracks, competitions and other materials. They’re experts in the subject matter of the application and ensure its technical accuracy.
 * System designers and project managers – are basically the people who plan and design the system. They’re responsible for the overall design, development and completion of the application. They require leadership skills as well as technical knowledge about systems development.
 * Those skilled in the collection and editing of each of the media types – collection and editing of media types is an area that requires particular expertise. Depending upon the intended delivery mode, e.g. CD or Internet, collectors/editors are required to consider issues such as bandwidth and data transfer requirements, screen resolution and memory and processor demands to ensure the chosen media mode is sufficient to meet the application’s purpose.
 * Those skilled in design and layout – are required to ensure that the presentation of the application, screen layout, keyboard commands, flow of information and other such areas produce an ergonomically sound interactive application which meets its design goals.
 * Those with technical skills with the information technology being used – are required to assist developers and users of a computer system with questions relating to hardware and software maintenance, usage and repair and so on. In terms of development of multimedia systems, such skills would involve selecting, installing and configuring appropriate hardware and software.

Education and Training
Multimedia is excellent for educational purposes as it uses different methods of display whereas animations provide changing scenes, text and subtitles assist the students who are hearing impaired and sound can assist those with sight disabilities. Multimedia offers education at an individual level with desired speed and convenience. Students can be trained via the Internet through multimedia terminals at home. Multimedia education is thus interactive assistance in developing student’s skills by educating and informing them. Its components are: Data and Information (text, images and video that combine to produce structured activities the user views as information, more emphasis will be on text-based information), Participants (teachers and students, parents and siblings, they will also be using the system), IT (high resolution VDU, audio speakers, CD/DVD drive, sufficient RAM and reasonably fast processor, keyboard and mouse for children’s click n drag, headphones) and Relationships (the direct user, the students who are also the participants, will control the path taken through applications as they select from the interactive menu via a mouse or keyboard and use the multimedia CD to their own need, speed and preference).

Leisure and Entertainment
Electronic games, 3D adventure games, sporting games and interactive movies have become extremely popular forms of multimedia applications due to their high level of interactivity. The new generation of games provide ingenious levels of interactivity and realism to captivate the user thus they based mainly on animations and videos rather than text due to their entertainment purposes. The components are: Data and information (realistic videos, animations and sounds with limited text), Participants (game players, ordinary people of all ages and abilities, more likely to be children and teenagers), IT (peripherals such as joystick, mouse, keyboard and track-pad, high resolution VDUs, high quality audio speakers, CD and DVD drive) and Relationship (the participants are also the players who play the games for leisure using a joystick etc. and make their own choices via navigational and hidden hypermedia).

Information
Multimedia has been used to provide guidance through the use of information centres in locations like museums, airports, rail stations etc. They’re aimed at quickly providing very basic information. An information kiosk allows the user to obtain specific information without asking a stranger like location details, product availability, arrivals and departures are all examples of information that can presented in this format. Its components are: Data and information (text with graphics and signs to provide basic information, audio to give directions, simple navigational options with little text, hypermedia to provide basic details), Participants (general public who happen to visit an information kiosk, travellers, tourists etc.), IT (touch screen for ease of using multimedia computer, trackball built into the system, display terminals including high resolution VDUs and monitors, laser screens) and Relationships (the general public is also the participant as they use hypermedia via touch screens to obtain basic information).

Virtual Reality and Simulation
Simulation is designed to duplicate real situations so user can gain valuable training and experience from using the system. It represents the behaviour of physical or abstract systems to help pilots and drivers to deal with various real-life situations in a safe environment. Virtual reality is a computer-generated artificial reality that projects a person into a sensation of 3 dimensional space, it convinces the user that they are part of a real situation. Components are: Data and information (audio and video to represent situations, in a VR – a 3D video headset will allow user to feel the reality) Participants (simulation – pilots and specialists to further knowledge and training, VR- ordinary people who play games etc.), IT (high resolution VDUs, simulator – keyboard and controls to interact with the flight’s cockpit, VR - joystick, mouse and keyboard) and Relationships (both participants are also the users as they interact with the system via a keyboard or joystick). the earth is flat

Combined Areas
This is where multimedia applications provide leisure as well as educational value through games that seek to interact with the student and make learning fun. Games such as building blocks by using times table is one such example. In this multimedia, text will be limited but animation and video will be emphasised to make learning fun and interactive. The data and information (limited text, animation, audio and video), Participants (students, teachers) IT (joystick, mouse, high resolution VDUs etc.).

The Worldwide Web
Appearing in 1993, www was the first method of sharing and linking text documents over the Internet, it was the 1st widely available hypertext system that could be used by people with totally different computer systems. It has made it extremely easy for large number of people to access multimedia systems stored as a series of linked webpages. Continued improvement in communication speed (or bandwidth) through technologies such as cable, ADSL and satellite have made the presentation of multimedia content via Internet a viable option. It has overcome the slow download speeds particularly for pages with graphic, sound and video. With an advanced ADSL connection, these data types can be downloaded within seconds and have improved communication capacity.

Optical Discs

 * CD-ROM speed – this stands for compact disk-read only memory and is an optical disk format that is used to hold pre-recorded text, graphics and sounds which can be run many times by purchaser. Before it had a single speed drive with the ability to access data at 150Kb p/sec. Through improved technology its now possible to purchase drives that are 40 or 60 times faster and the faster the drive spins, the more quickly it is able to deliver information to the processor. This improvement effectively began the multimedia revolution due to the sudden availability of high capacity random access data storage offering better quality animations. CD-RW or Compact Disk Re-writable allows the content stored on the disk to be overwritten and deleted as needed
 * Digital Video Disc – this is what DVD originally stood for but now it stands for digital versatile disc. The enormous storage capacity of a DVD means that a single disc can store an entire movie, with extra scenes, multi- language options etc. A DVD can store anything from an encyclopaedia, interactive and far realistic games, complete training systems and complex simulations. Its biggest advantage over CD-ROM is greater storage capacity allowing up to 17Gb of data to be stored in contrast which is 28 CDs in every DVD. Increased storage means increased flexibility for multimedia developers, so it will replace CD-ROM and VHS for most applications.

Screens
Screens: CRT displays, LCD displays and touch screens – A CRT is the most commonly used graphic display device. A Cathode Ray Tube is a sealed vacuum chamber that can fire and accurately focus beams of electrons on a chemically coated screen. A LCD (liquid crystal display) is an electro-optical device used to display digits, characters or images that uses transistors and a complex chemical solution to display each pixel. LCDs use a thin layer of liquid crystal material that changes electrical properties when electric current is applied, thus light is either blocked or allowed to pass through. Each area of the screen that represents a pixel can be individually affected. LCDs are smaller in size and weight with considerable savings in power, more clarity and resolution than CRTs but are more expensive. A touch screen is a computer display screen that is sensitive to human touch, allowing a user to interact by touching pictures or words on screen. They are used in information kiosks, in computer-based training services, and in systems designed to help impaired individuals with difficulty using a mouse or keyboard.

Projection Devices
this allows the projection of video and graphic images onto a screen. It produces an electronic image onto another medium. They were once very expensive and only worked in very dark rooms though still expensive, the projectors can display very bright light and clear high-resolution images in broad daylight. They’re now common in sporting and mass entertainment events or classroom teachers. It contains a chip with up to 500,000 mirrors which can individually controlled. By shining a bright light onto the chip while supplying its electrical circuits with a TV signal (from a camera, VCR or computer) the chip is able to create an image that can be projected onto a screen.

Speakers
sound has become an important part of a multimedia presentation as PCs are sold with high quality speakers. Sound special effects, particularly those giving ‘3D’ sounds are now common in computer games. The sound cards in most multimedia PCs can also play and create both MIDI and waveform files. Speakers provide the cheapest and easiest output device for audio but the quality matters. A sound card is needed for digital audio output and convert binary data into information by producing a digitised sound.

Heads-Up Displays
Virtual reality often uses a headset to give the wearer a 3D image and stereo sound. It removes all the other outside distractions so that the user’s senses of sight and sound are totally dominated by the artificial sound. Two VDUs are used in the headset, each giving the user a slightly different perspective view of the same scene. When the brain combines the 2 images, a realistic 3D view is created. Head up displays are smaller, less intrusive version of the headset developed for use by pilots.

Presentation Software
These use graphics and data/information from other software to communicate and make presentations of data to others assisting users in making automated slide presentations. The PowerPoint is an example of presentation software. Modern presentation software allow the creation of a professional looking multimedia with just a few clicks and these presentations They can incorporate text, numbers, images, audio, animation and video and allow relatively fast generation of a series of linked screens. They can be viewed using a standard monitor, data projector for a large group, hard copies of slides and transparencies and hard copies of paper handouts.

Application Software
Application software is a computer program used for a specific task. They allow you to add the elements of multimedia into just about any document. Programs like Word (used to produce word processed documents), and Adobe Photoshop (used to generate complicated graphical images) can be used to generate content that can be incorporated into a multimedia project. Digital video editing packages for computer systems allow user to create transitions, titles and sound, and to record sound and video clips but are expensive with high quality. Video or sound can even be imported by some word processing software. Specialist multimedia application software like Windows Media Player or Real Jukebox allows sound and video files to be displayed.

Authoring Software
These multimedia software are new that incorporate many features of stand-alone applications. They allow users to create multimedia using both static and dynamic media and records the final product onto CD, DVD, tape, a computer hard drive or other electronic media. Authoring software allows the user to sequence and time the occurrence of events determining which graphics, sound, text and video files are to be utilised at any given point in the final product and allows creator to determine the level of user interaction. Examples include Macromedia Authorware and Adobe Acrobat.

Animation Software
This software eases the burden of drawing the hundreds of cells or frames required for even a simple animation. There’s a wide range of animation software available each with weaknesses and strengths, but the majority provide the tools to produce an animation using 1 of the different animation techniques, including traditional frame-by-frame, path-based, morphing or warping e.g. GIFAnimator. Programming languages e.g. Consumption++ and Java are used to create high quality professional multimedia applications.

Web Browsers/HTML Editors
These are known as scripting software packages that allow the development of quite sophisticated multimedia applications. A web browser is software that allows you to browse through and view the thousands of websites that exist on WWW such as Internet Explorer. Editors allow the generation of pages on the Web and range from simple text-based programs which require coding of HTML to WYSIWYG systems like Macromedia Dreamweaver which allow coding to be generated without direct user intervention. HTML (Hypertext Markup Language) is the language or code that is written on pages on the Web. Web browsers and HTML editors assist users in creating and editing multimedia material for the WWW and for locating and viewing material on the Web.

Collecting

 * Text and numbers in digital format – for use on computer, data needs to be converted into binary numbers – digitisation – which is done by coding. ASCII is a standard 7bit code that represents 128 letters, numbers and punctuations as a 7bit binary number with 0s and 1s.
 * Audio, video and images in analog format – these three data types in the real world are referred to as analog data and fill the physical environment that surrounds us. They have continuous values and an analog signal is an electrical signal in the form of a wave. Analog or real world data must be converted to digital for processing by a computer after collecting it as digital data represents the computer world.
 * Methods for digitising analog data – audio is digitised via sampling where regular measurements are taken of the sound. Video data is displayed by the piped video system where a video card receives and translates the video data in a form that can be displayed over the screen. Capturing full motion video requires a video capture card to digitise the signal before storing on disk for later editing. Analog video data also undergoes the sampling process where a video digitiser measures and records signals that represent colours and light intensities where in contrast to audio sampling, the quantity of data that the video digitiser handles is considerably larger. Digitising an image involves converting it into bit patterns within a computer’s memory which can be edited, manipulated and improved. Optical scanners and video digitisers convert images into bit patterns by making many measurements of the signal coming. An optical scanner is a digitising device that shines an intense beam of light at a paper document. The light detectors inside the scanner measured the intensities and colours of the reflected light and analog to digital converters then turn these measurements into digital bit patterns that can be stored for later use.

Organising Multimedia Presentations
a storyboard is an illustrated scene-by-scene layout of the multimedia presentation showing the sequence of events and navigational links:
 * Linear – the user moves sequentially through the multimedia presentation where only options are back and forward. It’s ideal for testing presentations where 1 task must be finished before moving on to next one.
 * Hierarchical – this allows the user to choose from multiple options. The information is presented in a linear format but the user can choose which direction to take allowing them to explore more in detail. It’s ideal for information or leisure related tasks where at each stage, multiple options are provided.
 * Non-linear – allows the freedom to move in any direction within the structure at any time. They choose any path without significant restriction. Ideal for content presentations like multimedia encyclopaedia.
 * A combination of these – composite layout is where each of the 3 structures are combined. It includes a linear, non-linear and hierarchical structure.

Processing for a Multimedia System
involves the manipulation of data as collected data is imported into multimedia software which use compression techniques to minimise data transfer rates, bandwidth and storage requirements.

Data Integration or Hypermedia
The integration of text and/or number, audio, image and/or video – multimedia by definition consists of information presented in various forms including text, numbers, audio, images and video. Thus integration occurs in multimedia where items of data from a range of forms of information are combined together leading to increased storage requirements. The solution of course is compression to reduce redundant data.

Compression and Decompression
Compression and decompression of audio, video and images – the 3 data types are compressed to reduce their file size thus the storage capacity and the processing required. In compressing a file, processing occurs when the multimedia is moved from a secondary storage (like hard disk or CD-ROM) into the system RAM. Because multimedia contains enormous amounts of data, processing is an elemental part of creation.

Compression methods can be categorised into two categories: lossy, where some of the original data is lost in compression, and lossless, where no data is lost in compression.

Hypermedia
Hypermedia is the linking of multiple mediums to each other. Hypermedia is often utilized in multimedia and refers to the linking of data types. For example, activating a particular object on a website may cause additional text to be displayed, cause the user to ‘jump’ to a different section of the program, or to cause a video clip to play. The term ‘hyper’ refers to a link between elements of the program and so hypertext for instance is text that links to new information.

Storing and Retrieving

 * The different file formats use to store different types of data – images, audio and video can be stored in a wide variety of formats. For text and numbers: ASCII, RTF (Rich Text Format), TXT and DOC are available. For images: JPEG (Joint Photographic Experts Group) compresses images, GIF (Graphics Interchange Format) compresses images, BMP (Bit Map) uncompressed bit-mapped file format that increases size and HTML is a text based language used to create documents on web for images, text, audio and video. For audio: WAV (wave file) uncompressed sound format with large sizes but very common, MIDI (Musical Instrument Digital Interface) has small file size and is common, MP3 (MPEG Audio Layer 3) compresses file size greatly with high quality and easy to create and QuickTime which supports both wav and MIDI but uncompressed. For video: QuickTime which supports multiple file formats but has poor compression creating larger files, MPEG (Motion Pictures Experts Group) has very high compression and is standard for moving images and AVI (Audio Video Interleave) is the standard for digital video and common format but large size.
 * Compression and decompression – compression reduces the quantity of data in a file by a variety of methods. Audio files are compressed to reduce their storage space and transmission time and popular format is MPEG-1 audio layer 3 or MP3 – it uses lossy compression technique with little loss of quality. Video compression is achieved by use of codec a compression/decompression algorithm which is the method used to compress and then restore a data file. A number of video codes are in use including MPEG-1, -2 and -3 created by the Moving Pictures Expert Group. Image compression involves minimising the size in bytes of a file without degrading the quality of the image to an unacceptable level. This reduction in file allows more information to be stored in a given amount of disk or memory space, it also reduces the time required for information to be sent over Internet. Compression schemes can be lossless (where the decompressed data is identical to the original data with nothing lost in transaction such as GIF) and lossy (where the decompressed data is slightly different from the original e.g. JPEG and MPEG-1). Decompression, or the expansion of a compressed file, is only possible if a lossless compression scheme is utilised. So it’s only possible to expand a compressed file format to the original data set if the compression algorithm doesn’t discard information in the original compression process.

==Issues Related to Multimedia Systems==

Copyright
Copyright is the ownership of intellectual property. It is illegal to copy or reproduce a multimedia work without the express permission of the author. The particular issue with computer programs is that they’re relatively easy to copy and modify digital data with the appropriate tools. This becomes an ethical issue for users who have the technology to break copyright and avoid detection. The author of a saleable item has the right to expect a just a reward for their efforts. Another aspect of this is the need for the developer to fully acknowledge all sources that they use. E.g. if a multimedia encyclopaedia developer produced a program without acknowledging external sources of information and images, then they’re contravening copyright laws. When original work is produced using published sources, the author, URL address, date of publication, publisher, etc. should be acknowledged. The digital data in multimedia is easy to locate copy and edit.

Appropriate use of the Internet
appropriate use of Internet and other multimedia contents involves the issues of ethics and moral behaviour. As communications technology improves and new uses of Internet appear, like netbanking, there are many opportunities of misuse and abuse. Materials can be easily copied and presented as original work without acknowledging. In using the Internet, ethical considerations such as privacy need to be addressed as it’s a common practice for people and organisations to set up video cameras and streamline video on Internet. People captured on video may not want to be displayed worldwide on personal screens. The placement of pornographic images and other disturbing materials within the reach of young people browsing the Internet raises legal and ethical issues, as does the presence of flashing hyperlinks indiscriminately tempting Internet users of all ages to visit casino websites.

Merging Technologies
the increasing usage of digitisation due to digital convergence where content can be stored as a digital file rather than the more traditional analog form in multimedia has merged communications via radio, TV telephones, computers, the Internet and other modes into one. Web-TV allows the TV to act as a monitor connected to Internet; telephony is also possible with Internet using a sound card, microphone, PC and Internet to communicate as audio-conferencing. Desktop radio broadcasting is available on the Internet and audio and video files are available as streaming audio/video allowing you to listen or view video while it is being downloaded for playing at a later stage. Streaming technology has allowed the development of online broadcasting and WebTV.

Data Integrity of Source Data
data integrity is the accuracy, consistency, currency and reliability of the data. The integrity of data becomes more important as amount of information on Internet increases. Sometimes browsers will be unaware that the information on a website is dated if site hasn’t been updated. Publishing on the Internet is less formal and can be done by anyone with appropriate technology so data can be anything pretending to be fact. Integrity and accuracy is vital in a multimedia application designed to educate. An educational multimedia should provide a bibliography and identify its sources so that the accuracy of its information can be checked. The publishers of the Encyclopædia Britannica, who have print, CR-ROM, and online versions of their world-renowned reference materials available, could choose to use data from questionable sources but don’t instead they ensure the integrity of their product. However, overtime the accuracy of their factual information diminishes which is why they reproduce yearly editions. If the aim is information, such as a multimedia kiosk, then integrity will be judged by ease of use and honesty where accuracy is important but the need to check for sources is rarely an issue. If the aim of multimedia is entertainment, then factual accuracy isn’t important but integrity is judged by speed, reliability and variety of the games. In a training simulation (and VR), integrity will be judged by how closely the simulations match reality and to what extent its presents the users with a realistic experience otherwise it’ll be of little value.


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HSC Information Processing and Technology/Exam Work

Key Words used in HSC Exam Questions
Account: Account for, state reasons for, report on. Give an account of: narrate a series of events or transactions

Example Question:

Analyse: Identify components and the relationship between them: draw out and relate implications

Example Question:

Apply: Use, utilise, employ in a particular situation

Example Question:

Appreciate: Make a judgement about the value of

Example Question:

Asses: Make a judgement of value, quality, outcomes, results or size

Example Question:

Calculate: Ascertain/determine from given facts, figures or information

Example Question:

Clarify: Make clear or plain

Example Question:

Classify: Arrange or include in classes/categories

Example Question:

Compare: Show how things are similar or different

Example Question:

Construct: Make; build; put together items or arguments

Example Question:

Contrast: Show how things are different or opposite

Example Question:

Critically (Analyse/Evaluate): Add a degree or level of accuracy, depth, knowledge and understanding, logic, questioning, reflection and quality to (analysis/evaluation)

Example Question:

Deduce: Draw conclusions

Example Question:

Define: State meaning and identify essential qualities

Example Question:

Demonstrate: Show by example

Example Question:

Describe: Provide characteristics and features

Example Question:

Discuss: Identify issues and provide points for and/or against

Example Question:

Distinguish: Recognise or note/indicate as being distinct or different from; to note differences between

Example Question:

Evaluate: Make a judgement based on criteria; determine the valuof

Example Question:

Examine: Inquire into

Example Question:

Explain: Relate cause and effect; make the relationships betweethings evident; provide why and/or how

Example Question:

Extract: Choose relevant and/or appropriate details

Example Question:

Extrapolate: Infer from what is known

Example Question:

Identify: Recognise and name

Example Question:

Interpret: Draw meaning from

Example Question:

Investigate: Plan, inquire into and draw conclusions about

Example Question:

Justify: Support an argument or conclusion

Example Question:

Outline: Sketch in general terms; indicate the main features of

Example Question:

Predict: Suggest what may happen based on available information

Example Question:

Propose: Put forward (for example a point of view, idea, argument or suggestion) for consideration or action

Example Question:

Recall: Present remembered ideas, facts or experiences

Example Question:

Recommend: Provide reasons in favour

Example Question:

Recount: Retell a series of events

Example Question:

Summarise: Express concisely the relevant details

Example Question:

Synthesise: Putting together various elements to make a whole

Example Question:


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Talk:Guide to English Literature

Thank you for your lovely information about this topic .I am really happy to read it.

Formatting Given that this is a "draft," I acknowledge that the content needs a lot of fine-tuning. However, I am quite surprised at the improper utilization of bolding and italics in the article. Titles of books should be italicized, according to the rules of the English language--not bolded. The bolding option is overused to the point of making my eyes hurt. Oh, and Henrik Ibsen was not an English writer. He was Norwegian. -- Cqbarton (talk) 23:58, 7 June 2010 (UTC)

Rhyming epics?
Since when do classical epics have rhyming couplets? Neither the Iliad, nor the Odyssey, nor the Aeneid, nor Paradise Lost rhyme. Classical Greek and Latin don't rhyme as a rule, and Milton hated rhyme. The rest of this "Guide" is pretty much as informative as that segment. - Sukidakara (talk) 23:38, 16 January 2010 (UTC)

Title I suggest we change the name into The Occasional Reader's Guide to English Literature. --80.121.38.30 (talk) 13:42, 15 February 2010 (UTC)

title: Talk:Guide to English Literature


text:
Celestia/Catalog File Reference

Types of Catalog Files
Celestia's universe contains three broad categories of objects:

 * Stars (STC)
 * Deep sky objects (galaxies and nebulae) (DSC)
 * Solar system bodies (planets, moons, asteroids, comets, and spacecraft) (SSC)

Each is defined in a different type of catalog file. Solar system catalog (.ssc) files contain definitions for solar system bodies; .dsc files contain definitions for deep sky objects; and stars may be defined in either .stc files or in stars.dat, which is in binary format. A binary star format is used because Celestia's universe contains many more stars than deep sky objects or solar system bodies, so having a compact, quickly loadable format is very important.

Common Syntax of Catalog Files
Except for binary .DAT star catalogs, all other catalogs are text files that contain lists of object definitions of a similar format. Each definition has a name followed by a list of properties. Property lists are a collection of name and value pairs grouped by braces. Here is the list of properties for the star Proxima Centauri:

{   RA 217.429167 Dec -62.679444 Distance 4.225 SpectralType "M5.5V" AppMag 11.09 }

The property names are particular to the type of object. Property values have a type. In the example above, all of the properties are numbers except for the SpectralType which is a string. Celestia catalog files may contain comments -- any text between a hash character (#) and the end of a line is ignored.

Number Values
A number in a Celestia catalog file is a scalar real value. Very large or small values can be written in C-like exponential form, e.g. 1.2e-3 instead of .0012. Examples of valid number values:

1234 3.14159265 1.234e10 0.1025 -2.24 .1025 (Celestia v1.5.0 or later) +2.24 (Celestia v1.5.0 or later)

Note: Celestia v1.4.1 and earlier versions have two restrictions which have been fixed in v1.5.0. In Celestia v1.4.1 and earlier, all numbers must start with either a numeric character or a minus sign. A leading decimal point or a leading + should not be used. That is, values less than 1 must have a leading 0: 0.5 is OK, but .5 is not. Also, a leading + is assumed. Providing one will cause an error.

String Values
Strings are arbitrarily long sequences of characters enclosed by double quotes. They can span multiple lines, though any newlines inside a string will be interpreted literally. Some special characters may be represented by backslash-prefixed escape sequences.

 * \" : Double quote character
 * \n : Newline
 * \\ : Backslash
 * \u xxxx : Unicode character, where xxxx is a sequence of four hex digits

Vector Values
A vector in a Celestia catalog file is a list of three real values enclosed by square brackets. Example vectors:

[ 0 +1 0 ] [ 1.2 -3.4 5 ] [ 1.0e3 2.2 63 ]

Property List Values
Some properties in a list have complex values that are themselves property lists. Like top-level property lists, these are just brace enclosed lists of name-value pairs. Here is how you would set the value of the property named UniformRotation in a solar system catalog (.ssc) file:

UniformRotation {   Period 24.0 Inclination 23.5 }

(This is just an example to show the format. The directive UniformRotation is not recognized by Celestia v1.4.1 and earlier. It requires Celestia v1.5.0.)

Date Values
A date value may be written either as a number or as a string. A number is interpreted as a Julian day number. Date strings contain the Gregorian year, month, and day of the month. They may optionally have an hh:mm:ss formatted time. A 24-hour clock is used for the time. Negative year values are used instead of BC or BCE; if you want a date in 1 B.C., you should set the year to be zero. (This is the astronomical convention, which is not the same as the Christian convention used in most calendars. The Christian calendar has no year numbered 0.)

Examples of date values with explanatory comments:

2451545.0             # J2000 - noon January 1, 2000 2453023.1232 "2006 11 8"           # midnight November 8, 2006 "1984 12 25 1:30:00"  # 1:30am December 25, 1985 "-4 8 23 10:00:00"    # 10:00am August 23, 5 B.C. "2130 4 1 22:10:34.15" # 22:10:34.15 April 1, 2130

Starting with Celestia v1.5.0, all catalog times are specified using the TDB (Barycentric Dynamical Time) time scale. However, the on-screen time is shown in UTC. TDB is offset from UTC (Coordinated Universal Time) by 32.184 seconds plus some integer number of leap seconds. As of 2006, TDB is 65.184 seconds ahead of UTC. For further information, see the page on time scales.

title: Celestia/Catalog File Reference


text:
Celestia/Time Scales

UTC vs TDB
Versions of Celestia before v1.5.0 use UTC to calculate times and positions. Unfortunately, UTC includes "leap seconds" in order to stay aligned with the Earth's varying rotation. Leap seconds happen essentially randomly, when they are needed. Although Celestia does incorporate a table of leap second times, its use of UTC causes problems when used with ephemerides which are defined using TDB. Starting with v1.5.0, although it still displays UTC on the screen, Celestia uses the TDB time scale internally for everything else. As a result, Celestia places objects much more accurately than before.

Time Scales
It may be helpful for Celestia users to understand the various time scales that are used in the field of astronomy. The most familiar is local time, which is probably what you see if you look at a nearby clock. The local time zone determines the difference between local time and Coordinated Universal Time, or UTC. UTC is the current time at the zero degree meridian; it replaces Greenwich Mean Time as the standard world clock.

Astronomical ephemerides are typically defined in terms of Barycentric Dynamical Time, or TDB. TDB is the time measured by a clock at the solar system barycenter. It differs from Terrestrial Time (TT)--the time measured by a clock on the Earth--because of relativistic effects, but the difference between the two scales is always less than 0.002 seconds. The two scales can usually be considered equivalent in Celestia.

TT is ahead of International Atomic Time (TAI) by constant value of 32.184 seconds. Finally, UTC differs from TAI by some integer number of leap seconds. Leap seconds are inserted occasionally because the Earth's rotation is irregular, and it's desirable to keep our everyday time scale from drifting with respect to the terrestrial day-night cycle--except at the poles, the sun should be in the sky at noon. The most recent leap second occurred at 23:59:60 on December 31, 2016 and made UTC 37 seconds behind TAI. (See Wikipedia on TAI)

To briefly summarize the relationship between time scales: TT = TAI + 32.184 TAI = UTC + leap second count Thus, TT = UTC + 32.184 + leap second count

UTC is used in the Celestia's Set Time dialog and it's also the time displayed in the upper right of the screen. Unless you're creating scripts or add-ons for Celestia, UTC is all that you will see. But everywhere else, the time scale is TDB: xyz trajectory files, attitude files, beginning, ending, and epoch times in .ssc files.

title: Celestia/Time Scales


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HSC Information Processing and Technology/The Course

Aim
Information Processes and Technology Stage 6 is designed to enable students to become confident, competent, discriminating and ethical users of information technologies, to possess an understanding of information processes and to appreciate the effect of information systems on society.

Objectives
Students will develop:
 * 1) knowledge and understanding of the nature and function of information systems
 * 2) knowledge and understanding of interrelationships among information processes
 * 3) an understanding and appreciation of social and ethical issues pertaining to information systems, technologies and processes
 * 4) an understanding and appreciation of the emerging nature of information systems, technologies and processes within a historical context
 * 5) skills in the discriminatory selection and ethical use of appropriate resources and tools to support information systems
 * 6) skills and techniques to creatively and methodically plan, design and implement information systems to address needs
 * 7) skills in management, communication and teamwork in relation to individual and group activities.

Course Structure
The arrangement and relationship between components of the Preliminary course and the HSC course for Information Processes and Technology Stage 6 are outlined below. The percentage values refer to indicative course time.


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User talk:Mike.the.kitty

Hello and welcome to Wikibooks!

Here are some tips to help you get started:
 * You can sign your name on Talk and vote pages using four tildes, like this: ~~~~.
 * Remember to conduct any editing experiments in the sandbox.
 * If you're a Wikipedian, see Wikibooks for Wikipedians for a primer on how things work here (it's a little different).
 * If you want to base your work here on materials from Wikipedia, please use WB:RFI to bring the material over in compliance with the GFDL.
 * If you're an instructor and plan on using wikibooks for a class project, see Guidelines for class projects
 * Please say hello at the Staff Lounge with any questions or ideas.
 * Eventually, you might want to read the Manual of Style and Policies and Guidelines.
 * Please take a look at Naming policy before starting a new book.
 * Remember to maintain a Neutral point of view.
 * Explore, be bold in editing pages, and have fun!

You will find more resources in Community Portal. If you want to ask a question, visit the Study help desk, the Staff lounge, IRC channel or ask me personally on my talk page.

Good luck! -- Herby talk thyme 08:13, 8 November 2006 (UTC)

Image:SumerianZiggurat.jpg is missing license or source information

 * Please note that you need to correct the source and provide license info for this one. – Mike.lifeguard  | talk 18:14, 13 May 2008 (UTC)

Image:SumerianBulls.jpg is missing license or source information

 * This one is, I think. Please confirm and update the page. – Mike.lifeguard  | talk 18:16, 13 May 2008 (UTC)

Image:SumerianZiggurat.jpg is missing license or source information
Still missing a license template :) – Mike.lifeguard  | talk 20:49, 15 May 2008 (UTC)
 * Image:SumerianBulls.jpg too. – Mike.lifeguard  | talk 20:50, 15 May 2008 (UTC)

title: User talk:Mike.the.kitty


text:
User talk:Applehistory

Hello and welcome to Wikibooks!

Here are some tips to help you get started:
 * You can sign your name on Talk and vote pages using four tildes, like this: ~~~~.
 * Remember to conduct any editing experiments in the sandbox.
 * If you're a Wikipedian, see Wikibooks for Wikipedians for a primer on how things work here (it's a little different).
 * If you want to base your work here on materials from Wikipedia, please use WB:RFI to bring the material over in compliance with the GFDL.
 * If you're an instructor and plan on using wikibooks for a class project, see Guidelines for class projects
 * Please say hello at the Staff Lounge with any questions or ideas.
 * Eventually, you might want to read the Manual of Style and Policies and Guidelines.
 * Please take a look at Naming policy before starting a new book.
 * Remember to maintain a Neutral point of view.
 * Explore, be bold in editing pages, and have fun!

You will find more resources in Community Portal. If you want to ask a question, visit the Study help desk, the Staff lounge, IRC channel or ask me personally on my talk page.

Good luck! -- Herby talk thyme 08:16, 8 November 2006 (UTC)

title: User talk:Applehistory