TYPES OF NETWORKS TOPOLOGIES

Types of network topologies

BUS TOPOLOGY

A bus topology consists of a single central cable called the backbone to which all computers and other devices connect. It acts as the main physical pathway or central cable where all other devices are connected. All nodes share the backbone to communicate with each other on the network. Sometimes, a bus network has more than one server. Sometimes, a server is not needed on the network.

The bus transmits data, instructions, and information in both directions. When the sending device transmits data, the address of the receiving device is included with the transmission so that data is routed to the appropriate receiving device.

An advantage of the bus network is that computers or other devices can be attached or detached at any point without disrupting the network. If one of the nodes fails, the transmission simply bypass the faulty device and the bus network would still function as long as the backbone is working. Other advantage include easy implementation and extension, comparatively cheaper since the use of cable is minimal, able faults are easily identified.

The disadvantages however are due to limited cable length and number of stations, if there is a problem with the cable, the entire network fails, maintenance cost is higher in the long run, performance degrades as additional computers are added or with heavy traffic and proper termination is required.

RING TOPOLOGY

A ring topology consists of all computers and other devices that are connected in a loop. Ring topology is also known as a ring network. In a ring network each node directly connects to two neighbouring nodes. Data transmitted on the ring network travels from device to device around the entire ring in one direction only.

When a computer or device sends data, it will travel to each computer in the ring network until it reaches its destination. If a computer or device in the network fails, all devices before the failed device are unaffected, but thos after will not function. The ring network can span a larger area than a bus network but is more difficult to install.

A server may exist in a ring network, but it will not connect to all the nodes in the network. The server, like other nodes, will only communicate to its two neighbouring nodes. This type of topology is primarily used for LANs but can also function in WANs.

The advantages of this type of topology are :- minimal cable requirement, no wiring cabinet or closet needed, message can be automatically acknowledge, no data collision between nodes.

The disadvantages include network failure if any nodes goes down, troubleshooting is difficult because of the one way communication and the number of nodes and distances are limited.

STAR TOPOLOGY

In a star network, every node or devices are connected to a central device, usually a hub, that provides a common connection for the nodes.

All data transfers from one node to another will go through the hub. Data travels in both directions. Every node must connect to the hub in order to communicate. If one of the nodes fails, the star network can still function as long as the hub is working.

A star network is easier to install and maintain but it need more cables. Nodes can be added or removed from the network without disrupting the network. In other words is one node or device fails the network will not be affected. But if the hub fails the entire network will be down.

The advantages of this topology are :- its easy to install and set up, easy to detect or remove faulty devices, network is not affected by failed devices, easy to expand( add more nodes), easy to troubleshoot since the problems can be isolated and is more suited for a larger network.

The disadvantages are : - failure of central hub will result in network failure, cost more compared to bus or ring topologies and it requires more cable

SOFTWARE - Operating System (OS)

Types of Operating System (OS)

Operating system is a set of programs containing instructions that coordinate all the activities among the computer hardware resources. Most operating system performs similar functions that include starting booting a computer, managing memory and configuring devices. Some operating system also allow user to control a network and administer security measures.

• Stand-alone OS – WinXP, Windows Vista, Mac OS, Linux, Dos
• Networking Operating System (NOS) – Windows NT, Windows Server 2000, Linux, Unix, Solaris
• Embedded Operating System – Windows CE, Palm OS, Symbian OS, Embedded Linux.

Platforms For Operating System

PC Platform Operating Systems - The examples of operating systems used on PC platforms or IBM compatible computers are DOS used a command line interface when Microsoft first developed it. Microsoft Windows XP’s operating environment is a Graphical User Interface (GUI). Both are closed source software.

Apple Platform Operating Systems - The operating systems used on Apple platforms are Mac OS & Mac OS X. Mac OS was the first commercially successful graphical user interface. It is a closed source software and are targeted for use with home desktops and workstations. Mac OS X is a multitasking operating system and targeted for use with home desktops, workstations and servers. It also has better security protection compared to Mac OS, for example the integrated firewall utility.

Cross-Platform Operating Systems - Cross-platforms operating systems are UNIX and LINUX. UNIX is a multitasking operating system. Some versions of UNIX have a command line interface but most versions of UNIX offer a graphical user interface. Linux is a popular, free, UNIX-like graphical user interface operating system. It is an open source software. Linux provides a great deal of liberty to those that interact with Linux technology. Although Linux runs on many kinds of equipment, it is best known for its support of IBM-Intel PC-based hardware.

The Main Functions Of OS

• starting a computer
• providing a user interface
• managing data & program
• managing memory
• configuring devices

Starting the Computer - The first function of an operating system is to start the computer. This process is called booting. Booting means to load & initialize the operating system. It can happen in two ways: warm boot or cold boot.

• A warm boot means restarting a computer that is already on. It normally happens after installing a new software or hardware or after an application crashes or stops working.
• A cold boot means starting a computer that is already off. It happens when we turn on a computer that has been completely powered off.

Providing a User Interface - This function controls how the user enters data and instruction and how information is displayed. The three type of user interface are Command-Line, Menu-Driven and Graphical User Interface . The user interface typically enables users:

• to start an application program
• to manage disks and files such as formatting, copying and renaming
• to shut down the computer safely by following the correct procedures

Managing Data & Programs - When we start an application, the CPU loads the application from storage into memory. In the early days, single-tasking operating systems could run only one application at a time. Multitasking operating systems enable users to work with two or more application programs at the same time.

Managing Memory - The computer's operating system is responsible for managing memory such as:

• optimizing the use of RAM
• allocating data & instruction to an area of memory while being processed
• monitoring the contents of memory
• releasing data & instructions from being monitored in memory when the process is done

Configuring Devices - Another function of an operating system is handling input and output, as well as enabling communication with input and output devices. Most operating systems come with drivers for popular input and output devices. These drivers install new devices and check whenever there is conflict with these devices.

Operating System Interface

The three type of user interface are Command-Line, Menu-Driven and Graphical User Interface.

COMMAND LINE USER INTERFACE

Command-Line User Interface

The command-line user interface requires a user to type commands or press special keys on the keyboard to enter data and instructions that instruct the operating system what to do. It has to be typed one line at a time.

It is difficult to use because it requires exact spelling, syntax or a set of rules of entering commands and punctuation. Complicated rules of syntax that specify exactly what you can type in a given place require memorization. It is also easy to make a typing mistake. The advantage of command-line interface is, it helps the user to operate the computer quickly after memorizing the keywords and syntax.

MENU DRIVEN USER INTERFACE

MENU DRIVEN USER INTERFACE

Menu-driven user interface enables the user to avoid memorizing keywords such as copy, paste and syntax. On-screen, menu-driven interface provide menus as means of entering commands. It shows all the options available at a given point in a form of text-based menu. Menu-driven user interfaces are easy to learn.

GRAPHICAL USER INTERFACE

Graphical User Interface (GUI) - GUI makes use of the computer’s graphics capabilities to make the operating system and programs easier to use, which is also called ‘user-friendly’. Today GUIs are used to create the desktop that appears after the operating system finishes loading into memory.

GUI is commonly used and has become a standard. It is easy to differentiate the interfaces between Mac OS, Windows XP or Linux by looking at their desktops. GUI with menus and visual images such as buttons, icons and other graphical objects to issue commands where many actions can be initiated by clicking icons that represent computer resources such as files, programs and network connections. On the desktop, we can initiate many actions by clicking the icons that represent the computer resources such as files, programs and network connections.

Differences Between Command-line Interface and Graphical User Interface

HARDWARE - Storage

Storage

Primary Storage (RAM, ROM) - Primary storage is the main memory in a computer. It stores data and programs that can be accessed directly by the processor. There are two types of primary storage which are RAM (Random-Access Memory) and ROM (Read-Only Memory). RAM is installed inside computers. RAM is also known as a working memory.

• Random-Access-Memory (RAM )- The data in RAM can be read (retrieved) or written (stored). RAM is volatile which means the programs and data in RAM are lost when the computer is powered off. Computer uses RAM to hold temporary instructions and data needed to complete tasks. This enables CPU to access instructions and data stored in the memory very quickly. RAM stores data during and after processing.
• Read-Only-Memory (ROM) - ROM is another type of memory permanently stored inside the computer. ROM is non-volatile. It holds the programs and data when the computer is powered off. Programs in ROM have been pre-recorded. It can only be stored by the manufacturer; once it is done, it cannot be changed. Many complex functions, such as start up operating instructions, translators for high-level languages & operating systems are placed in ROM memory. All the contents in ROM can be accessed and read but cannot be changed.

• 

Secondary Storage (magnetic medium optical medium, flash memory)

Secondary Storage is another alternative storage device to keep your work and documents. It is very useful to store programs and data for future use. It is installed externally. It is non-volatile, which means that it does not need power to maintain the information stored in it. It will store the information until it is erased.

Secondary storage can be divided into magnetic medium, optical medium and flash memory.

• Magnetic Medium - Magnetic medium is a non-volatile storage medium. It can be any type of storage medium that utilizes magnetic patterns to represent information. The devices use disks that are coated with magnetically sensitive material. The examples of magnetic storage are magnetic disk ( floppy disk, used for off-line storage, hard disk, used for secondary storage), magnetic tape ( video cassette, audio storage reel-to-reel tape & others)

• Optical Medium - Optical medium is a non-volatile storage media that holds content in digital form that are written and read by a laser. These media is usually a flat, circular portable disc which include various types of CDs and DVDs. These following forms are often commonly used:
• CD, CD-ROM, and DVD are a read-only storage, used for distribution of digital information such as music, video and computer programs.
• CD-R is a type of optical storage where it can be written once and cannot be erased or written over once it is saved.
• CD-RW, DVD-RW, and DVD-RAM allow data that have been saved to be erased and rewritten It is however slow to write but fast reading type of storage.

The disk capacity of optical media is more compared to magnetic media. Durability is another feature of optical media; they are able to last for up to seven times as long as traditional storage media.

• Flash Memory - Flash Memory is a solid-state, non-volatile, rewritable memory that functions like RAM and a hard disk drive combined. Flash memory store bits of electronic data in memory cells just like DRAM (Dynamic RAM), but it also works like a hard disk drive that when the power is turned off, the data remains in the memory. Flash memory cards and flash memory sticks are examples of flash memory.

Flash memory cards are also used with digital cellular phones, MP3 players, digital video cameras and other portable digital devices. Flash memory is also called USB drives, thumb drives, pen drives or flash drives, are the up-and-coming players in the portable storage market.

The advantages of flash memory are, it offers faster reading or access time compared to other secondary storage devices, (though not as fast as RAM) it is durable and requires low voltage. It is also light and small. The disadvantage is it is more expensive than the magnetic disk of the same capacity.

HARDWARE - Motherboard

MotherBoard

Motherboard is the main circuit board which has some electronic components attached to it and others built into it. CPU, expansion slots, expansion cards, RAM slots, ports and connectors are the components on the motherboard.

The location of the slots for central processing unit (CPU), expansion slots, expansion cards, RAM slots, ports and connectors

DIAGRAM FOR COMPONENTS OF A MOTHERBOARD AND LOCATION OF EXPANSION SLOTS AND PORTS

• PCI slots or expansion slot is a where expansion cards are attached to the motherboard. Examples of expansion cards are
• Video Graphic Accelerator Cards(VGA),
• Network Inteface Cards(NIC),
• TV Card or Audio Card
• Dimm Memory Channel or Ram slots is connector where RAM is inserted
• CPU Socket is where the CPU is housed ( on the diagram its labeled as mPGA 476 Socket)
• IDE connectors are for connecting hard disk or CDrom
• 
  

Ports and connectors

EXAMPLES OF PORTS

HARDWARE - input and output device

Input devices used for text, graphic, audio and video

Input devices are any hardware components that allow user to enter data and instructions into a computer.

Input Devices For Texts - Keyboard, virtual keyboard (on the screen) & an optical reader (uses a light source to read characters, marks and codes and then converts them into digital data that a computer can process e.g. barcode reader.

Input Devices For Graphics - Scanner is a device that captures images from photographic prints, posters, magazine pages and similar sources for computer editing and display. Digital camera allows you to take pictures and store the photographed images digitally.

Input Devices For Audio - Audio input can be speech, music or sound effects. Audio input devices are such microphone( to record or give command to the computer) and digital musical instruments like the Musical Instrument Digital Interface (MIDI) keyboard ( to play and record music ).

Input Devices For Video - Video input can be from a digital camera, webcam or Closed-Circuit Television (CCTV). CCTV video camera is a type of digital video camera that enables a home or small business user to capture video and still images. A webcam is any video camera that displays its output on a web page. A digital video camera allows you to record full motion and store the captured motion digitally.

Pointing Devices - A pointing device is another form of input device that enables the user to freely move an on-screen pointer to select text, menu options, icons, and other on-screen objects. Pointing devices such as a mouse (has buttons, a rolling ball or an optical reader), trackball ( a stationary device with a ball on top or at the side), joystick ( a vertical lever for control), gamepad (game controller held in both hands with thumbs and fingers to control), graphics tablet and touch screen ( used to input spatial data into the computer. Spatial data refers to data that is continuous and multi-dimensional).

Output devices used for text, graphic, audio and video

Output device is any device that is capable of delivering or showing information to one or more user. An output device shows prints and present the results of a computer’s work e.g. speaker, monitor, LCD projector, Printer, Plotter.

A monitor is an example of an output device that can be used to display text. It can also display graphics and video. It accepts video signals from a computer and displays information on its screen.

A printer is another example of an output device that can be used to print text, apart from graphics, on mediums such as paper, transparency film or even cloths. A photo printer is a colour printer that produces photo-lab-quality pictures.

An image setter produces high quality output compared to an ordinary laser printer. An image setter is a high resolution output device that can transfer electronic text and graphics directly to film, plates, or photo-sensitive paper.

A pair of speakers is an audio output device that generates sound. The headphone is a pair of small speakers placed over the ears and plugged into a port on the sound card. A woofer or subwoofer is used to boost the low bass sound and is connected to the port on the sound card.

A Liquid Crystal Display (LCD) projector uses its own light source to project what is displayed on the computer on a wall or projection screen. A digital light processing (DLP) projector uses tiny mirrors to reflect light which can be seen clearly in a well-lit room.

DATA MEASUREMENT..

The relationship of data representation

Bit - A bit is the smallest unit of data that the computer can process. Bit is a short for binary digit. A bit is represented by the numbers 1 and 0. These numbers represent the binary system. They correspond to the states of on and off, true and false, or yes and no. All digital data use the binary system to process the information. This information includes letters, digits or special character.

Byte - Byte is a unit of information built from bits. One byte is equals to 8 bits. Eight bits that are grouped together as a unit. A byte provides enough different combinations of 0s and 1s to represent 256 individual characters. One byte represents a single character such as the number 3, letter b or a $ symbol. Bits and bytes are the basis for representing all meaningful information and programs on computers.

Character - Computers does not understand letters, numbers, pictures or symbols. Computers uses binary system to count only as it only recognizes two states that are 0 and 1. A byte represents a single character in the computer. One character such as A, 7, 9 and + is eight bits that are grouped together. A byte provides enough different combinations of 0s and 1s to represent 256 individual characters. For example, the capital letter F is represented by the binary code 01000110 that can be understood by the computer system.

Coding Scheme

The combinations of 0’s and 1’s are defined by patterns. These patterns are called coding system or schemes. There are three character codes or coding schemes to represent characters which are ASCII,EBCDIC and Unicode. ASCII is most widely used for personal computers. EBCDIC was developed by IBM and is used primarily for large computers like mainframes and high end servers.

The 256 character capability of ASCII and EBCDIC is to small to handle characters that are used by other languages such as Arabic, Japanese and Chinese. The Unicode coding system are designed to solve this problem. It uses two bytes (16bits) combination to represent one character. This gives it capability to represent 65,536 different characters. This can cover all the world’s languages. Unicode is downward-compatible with ASCII meaning that Unicode can recognize ASCII

ASCII (American Standard Code for Information Interchange) was established to:

• To make it possible for humans to interact with a digital computer that processes only bits.
• achieve compatibility between various types of data processing equipment making it possible for the components to communicate with each other successfully.
• enables manufacturers to produce components that are assured to operate correctly in a computer.
• make it possible for humans to interact with a computer. It also enables users to purchase components that are compatible with their computer configurations

Units of data measurement

Bit - A bit is represented by the numbers 1 and 0. They correspond to the states of on and off, true and false, or yes and no.

Byte - 1 byte = 8 bit

Kilobyte (KB) - 1 KB = 1024 bytes or 1 KB = 2¹⁰ bytes

Megabyte (MB) - 1 MB = 1 048 576 bytes or 1 MB = 2²⁰ bytes

Gigabyte (GB) - 1 GB = 1 073 741 824 bytes 1 GB = 2³⁰ bytes

Terabyte (TB) - 1 TB = 1 099 511 627 776 bytes or 1 TB = 2⁴⁰ bytes

Note:

1 KB = 1 024 byte

1 MB = 1 024 KB = 1 048 576 byte

1 GB = 1 024 MB = 1 048 576 KB = 1 073 741 824 byte

1 TB = 1 024 GB = 1 048 576 MB = 1 073 741 824 KB = 1 099 511 627 776 byte

Units of clock speed measurement

Clock speed or computer speed means how fast a computer can process data. In other words, this means the speed the computer can turn data into information. It is measured by a system clock that is situated in the microprocessor.

The clock speed is measured in hertz which means once machine cycle per second. The speed of the system clock has no effect on the speed of printers or disk drives.

The combination of speed and number of paths determines the total processing speed or channel bandwidth as it is sometimes referred to. This is because different processors use different architecture.

For example:-

1.4 GHz Pentium 3à 1.4 GHz Pentium 4à 1.4 GHz Power PC G4

Hertz & Seconds

· A hertz is one cycle per second.

· Megahertz (MHz) – 1 Megahertz (MHz) equals to one million cycles of the system clock. (Mega is a prefix that stands for million. A computer that operates at 933 MHz has 933 million clock cycles in one second.)

· Gigahertz (GHz) -1 Gigahertz (GHz) equals to one billion cycles of the system clock. In relation with megahertz, 1.0GHz is equivalent to 1000 MHz. Giga is a prefix that stands for billion. GHz is most often used as a measurement of a PC processor chip and power, with bigger numbers meaning more speed and higher price. A microprocessor that runs at 200 GHz executes 200 billion cycles per second. For a 2.4 GHz machine . Its clock rate is 2.4 billion cycles per second.)

COMPUTER SYSTEM

Definition

A computer system is defined as an electronic device with a combination of components designed to accept(input) and process data according to specific rules(process) to produce results(output) which can be stored for future use(storage). A computer system consists of four major hardware components; input devices, output devices, processor and storage devices. A computer system requires hardware, software and a user to fully function.

Input - Input is any data or instructions that we enter into the computer system for processing. There are four types of input: which are text, graphic, audio and video. Example of input devices are keyboard, light pen, joystick, microphone, mouse, video & digital camera.

Process - The processing unit controls all activities within the system. The CPU is an

example of a processor. It has the same important as the brain to human being. The processor interprets and carries out the basic instructions that operate the computer. Example of processors or CPU are Pentium IV, AMD Athlon, G4.

Storage - Storage is a location which data, instruction and information are held for future use. It is the physical material that keeps data, instruction and information. There are two types of storage. They are the primary storage and secondary storage. The example of storage devices are RAM and ROM(primary storage), hardisk, Floppy Disk, diskette, CD ROM and DVD ROM(secondary storage).

Output - Output is data that has been processed into a useful form, called information. There are four types of output, which are texts, graphics, audio and video. Example of output devices are monitor, printer, speaker and plotter.

The information processing cycle

Input - Users input data or instruction into the computer system to be process. Input could be either text, graphic, audio or video. Input devices are used by users to input data. Input devices are any electronic device connected to a computer and produces input signals.

Process - Data or instruction being input into the computer system is then processed by the CPU which controls all activities within the system. The results of the processed data are then sent to an output device as usable data. Examples of CPU or processors are Intel Pentium 4, AMD K6 Athlon, Win Chip 2, Cyrix 686, Intel Celeron.

A CPU interprets the data and carries out the instructions by processing data and controlling the rest of the computer’s components. A CPU consists of two subcomponents; the Control Unit (CU) and the Arithmetic Logic Unit (ALU).

· CU or Control Unit main function is to direct the CPU to process data by extracting instructions from memory and decodes and executes them. It tells the rest of the computer system how to carry out the program’s instructions. It directs the movement of the electronic signals between the memory, which holds data, instructions and processed information, and the arithmetic logic unit. It also directs these control signals between the CPU and the I/O devices.

· The ALU or arithmetic-logic unit performs two types of operations: arithmetic and logic. Arithmetic operations are fundamental mathematical operations: addition, subtraction, multiplication and division. Logical operation consists of comparisons. That is two pieces of information or data are compared to see whether the result is equal, less than or greater than.

· The CPU manages a four-step basic operation which is called a machine cycle. The steps are Fetching, Decoding, Executing & Storing.

The Machine Cycle

Storage - Computer storage is important to help users store programs and data to be used at a later time. It is also useful to keep current data while being processed by the processor until the information is saved in a storage media such as a hard disk or a diskette. Computer storage also stores instructions from a computer program. There are two type of computer storage; primary storage and secondary storage.

• Primary storage is known as the main memory of a computer, including RAM (Random-Access Memory) and ROM (Read-Only Memory). It is an internal memory (inside the CPU) that can be accessed directly by the processor.
• Secondary storage an external storage that refers to various ways a computer can store program and data. Many complex functions, such as translators for high-level languages and operating systems are placed in primary storage. Secondary storage is an alternative storage. It is very useful to store programs and data for future use.

Output - Output is the result of data processing activity when it is presented external to the system. The output from a computer can be in a form for use by people, for example, printed or displayed. There are four types of output, which are texts, graphics, audio and video.

MULTIMEDIA DEVELOPMENT

Construct : S08 Multimedia Product Development

Aspect : LA4.S08.1 Apply All The Phases Of Multimedia Production To Produce An Interactive Educational Multimedia Project.

Type of Instrument : Project

----> PLEASE SUBMIT BEFORE FINAL EXAM..THANK U...

TYPES OF NETWORK ARCHITECTURE

Client/Server

A client/server network is a network in which the shared files and applications are stored in the server but network users (clients) can still store files on their individual PCs. On a client/server network, one computer acts as a server that provides services to the clients when requested by the clients.

A server is a computer that shares infor

mation and resources with other computers

on a network and also controls access to hardwares and softwares besides providing centralized storage for the softwares or computer programs. A client is a computer which requests services or files from a server computer.

A client/server network is typically used when there is a constant need to access large files and applications or when multiple users want to share peripherals computer that shares information and resources with other computers on a network and also controls access to hardwares and softwares besides providing centralized storage for the softwares or computer programs. A client is a computer which requests services or files from a server computer.

Peer-to-Peer

Peer-to-peer network is a simple, inexpensive network with all the nodes acting as both servers and clients. A PC can access files located on another PC and can also provide files to other PCs. With peer-to-peer network, no server is needed; each computer in the network is called a peer.

All computers in the peer-to-peer network has equal responsibilities and capabilities to use the resources available on the network. This type of network normally do not consist more than 10 connected computers.

Types of computer networks

Local Area Network (LAN)

LAN is a group of computers and network devices connected together, usually within the same building e.g.: within a school lab, office or your own home.. It is the smallest network compared to the other two networks. The simplest form of LAN is to connect two computers together. A network which consists of less than 500 interconnected devices across several buildings is still recognised as a LAN.

Inexpensive hardware used in LAN previously includes twisted pair, coaxial cables and the higher end is fiber optic or wireless. However, coaxial cables are now being replaced by a higher speed cabling system such as CAT5 using RJ45 connectors.

LAN is a very high speed network (from previously 10Mbps) to 100Mbps, which is faster than MAN and WAN.

Metropolitan Area Network (MAN)

MAN can be defined as a group of computers and network devices connected together within a large physical area It is a high speed network that connects a collection of LANs and handles a bulk of communication activities within a metropolitan area or the same geographical area, for instance a city e.g. within a city or town. Companies that have several branches within the Kuala Lumpur city such as banks, might find a MAN useful to them. In this case, setting up a MAN across long distances can be best connected using fiber optics.

MAN often acts as a high speed network (although not as fast as a LAN) to allow sharing of regional resources. However the area covered by a Man is relatively smaller than the area covered by WAN

Wide Area Network (WAN)

WAN is the largest network of all network types. It can be considered as a collection of LANs or MANs or the mix of two with a very large geographical area, for instance a country or even beyond the border e.g.: between KL and London. The Internet is the largest WAN in the world using combinations of many types of media such as telephone lines, cables and radio waves.

An example in the society using WAN is the banking organisation. Local banks have always maintained their business online by connecting all computers of their branches in the countries. International banks also use WAN to connect their computers all over the world. A device called a router is needed to connect the MANs and LANs all over a large physical area.

A router is a special networking device that connects two or more different networks and keeps data flowing between them. A router makes all the different networks communicate, such as connecting LAN to LAN, LAN to WAN or WAN to WAN. The transmission media in WAN uses the fibre optic cable. WAN is still considered a fast network with speeds 20 – 2000 Kbps, but slower than LAN and MAN.

Computer Networks And Communication

Definition

Computer network is a system of interconnected computers and peripheral devices. For example, it may connect computers, printers, scanners and cameras. Using hardware and software, these interconnected computing devices can communicate with each other through defined rules of data communications. In a network, computers can exchange and share information and resources. A computer network may operate on wired connections or wireless connections.

When two or more networks are linked or connected and are able to communicate with one another using suitable hardware and software, it is called an internetwork.

Communications is about the transfer of information from a sender, across a distance, to a receiver. Using electricity, radio waves or light, information and data in the form of codes are transmitted through a physical medium such as wire, cable, or even the atmosphere.

The information that is transmitted (sent) can be text, voice, sound, video, graphics and images, or a combination of all these, which we call multimedia. We transmit information or data by using two types of signals, namely analog and digital.

The importance of computer networks and communications.

Information is now made easy with the availability of network communications. In a clinic for example, network communications plays an important part in keeping patients’ database for easy retrieval. Unlike in conventional practice, doctors and nurses have to look for a patient’s personal file from hundreds or maybe thousands of records. With network communication, the clinic saves time and manpower. Allocation can be effectively planned.

The advantages of using a computer network are sharing devices such as printers and scanner, sharing programs or softwares, files, data, information, sharing single high-speed internet connection , accessing a server centered database, better communication using internet services like email, mailing list, chat programs. With computer networks users can carry out:-

E-Business - E-business refers to conducting business transactions on the internet, not only limited to buying and selling but also servicing customers and collaborating with business partners. E-business supports many types of business transactions, including online shopping, selling and renting. Users can browse the website and choose from the list of items or services to buy. Payment is usually via credit card.

Online Education - With a network connection, online education is made possible. Students at any location around the world can participate in an online classroom, download tutorial questions and submit their assignments.

E-Banking - E-banking handles all types of banking transactions like account management, fund transfer and payments primarily over the internet. User can pay bills, check the account balance and transfer money to other parties, using e-banking facilities twenty four hours a day and seven days a week. With e-banking, most of the transactions can be done at home or from the office, thus users save time on traveling and queuing at the bank counters.

Long Distance Communication - Long distance communication is made easy via network availability. Communication is possible via voice, text or video. The cost of having this type of communication is cheaper than making a normal phone call and definitely faster and more effective than corresponding via letters of fax. In business, important decisions can effectively made through video conference meeting.

CONSTANTS, VARIABLES, DATA TYPES

Form5 : Constants & Variables & Data Type

5 Basic elements in programming.

1. Constant.
2. Variable.
3. Data Type.
4. Operators.
5. Control Structures.

Constants
Constant is a data container that stores information. The value will never change (remains constant) at any time during the course of a program.

Declare is the official term used in programming to announce to the program
the condition of statement in programming.

Variables
Variable is a data container that stores information. The value inside may change at any time during the course of a program.

DATA EXAMPLES FOR DIFFERENT DATA TYPES

Data type determines the type of data a variable can store, for example a number or a character. Examples of data types are integer, double, string and boolean.

Integer
Integer data type contains any whole number value that does not have any fractional part.
This is how we declare an integer type constant in Visual Basic statement.
This is how we declare an integer type variable in Visual Basic statement.

Double
Any number value that may and could contain a fractional part.
This is how we declare a double type constant in Visual Basic statement.
String
Any value that contains a sequence of characters.
This is how we declare string type constant in Visual Basic statement.

Boolean
Boolean type consists either a True or False value. Programmers usually use it to store status.
This is how we declare a boolean type constant in Visual Basic statement.

LOGICAL OPERATORS, FLOW CHART, CONTROL STRUCTURE

Form 5 : Logical Operators, Flow Chart, Control Structure

FUNCTIONS OF LOGICAL OPERATORS
Logical operators are notations that tell the computer to perform logical operations.
Examples of Logical operation are: AND, OR, and NOT.
Logical operator compares 2 conditions and returns a TRUE or FALSE value.


AND operator
Notice that truth value of X AND Y is True ( 1 ) if only both X and Y are True ( 1 ).
Else it is false ( 0 )


OR operator
Notice that truth value of X OR Y is only True ( 1 ) if either X or Y are True ( 1 ) or both X and Y are true ( 1 )
Else it is false ( 0 )


NOT operator
The diagram shows the truth table of NOT operator NOT X is the negation of X, it is essentially the 1's complement operation.
Notice that truth value of NOT X is True
( 1 ) when X is False and vice versa.


FLOW CHART
Let’s identify some of the main elements in the flow chart. We have five main elements in a flow chart.

Flowline and arrowhead use to connect symbols and indicate the sequences of operation.
Input or output shows either an input operation (e.g. an INPUT from the
user) or an output operation (e.g. PRINT some messages).

Process shows a process to be carried out (e.g. calculation).
Decision shows a decision (or choice) to be made. The program should continue along one of two routes (e.g. if...else).

A flow chart is a diagram using symbols to show the step-by-step sequence of procedures in a program. A flow chart describes the logic and program flow of a computer program graphically.


CONTROL STRUCTURES
Control structure is a structure of statements in programming that allows
the programmer to control the flow of a program.
Control structure can be divided into sequence, selection and repetition control structures.


SEQUENCE CONTROL
Sequence control refers to the linear execution of codes within a program. In sequence control, the statements are executed one by one in consecutive order.
In sequence control, the statements are executed one by one in consecutive order.

This program will request the user’s date of birth and then request today’s date, calculate the age and finally will print the user’s age.
It will execute statement 1 followed by statement 2 and any following statements.


SELECTION CONTROL
There are times when you want your program to make a decision based on the situation given.
For example, a program that stores student’s marks may respond differently to different marks.
Or maybe a simple mathematical program will display its result as odd or even, based on the result.
Selection control enables the programmer to assign different events for different situations.

An example of selection control is “If...Then...Else” statement. The basic pseudo code for “If...Then...Else” statement is as follows.
A student requests her service hours in a library from the program, the
program will then check whether her service hours are more than/equal to 30 or not.

If the service hours are over or equal to 30, the program will print a message, “Thank you for your service”.

If the service hours are lower than 30 then the program will print a message, “Please continue to serve in the library”.

PROGRAM DEVELOPMENT PHASES

Form 5 : Five Program Development Phases

In program development, there are five main phases. These phases are a series of steps that programmers undertake to build computer programs. The program development phases guide computer programmers through the development of a program.

The five main phases of program development are as follows:

PROBLEM ANALYSIS PHASE
During the problem analysis phase, the programmer will interview the client to find out what the client’s needs are.

For example, the client might be a school that wishes to set up a school registration program. So the school administrator might tell the programmer that they need to record students’ data such as name, date of birth, gender, class, parents’ names, address and contact numbers.

PROGRAM DESIGN PHASE
Based on that, the programmer will design a flow chart that represents the needs of the client, which in this case is the school registration program.

CODING PHASE
Once the flow chart is confirmed, the programmer will perform coding.

TESTING AND DEBUGGING PHASE
The school registration program will be tested by the users at the client’s site. In this case, it will be the school office administrators. If there are any errors, the programmer will do a debugging of the program.

They either show up as you type the program code, or if you have turned off the automatic syntax error check, the syntax errors show up when you try to run or compile the program.


DOCUMENTATION PHASE
After this, the programmer will complete the documentation for the program; this includes the user manual, a clear layout of the input and output records and a program listing.

LATEST PROGRAMMING LANGUAGE

Form 5 : Latest Programming Language

THE LATEST TYPE OF PROGRAMMING LANGUAGES

1. FIFTH GENERATION LANGUAGES

Fifth generation programming language (5GL) is an advance programming language which concentrates on solving problems using constraints given to the program.

In fifth generation language, the programmer just need to define the problem to be solve and the program will automatically code the program based on the problem definition.

Fifth generation languages are designed to make the computer solve the problem for you.
Fifth generation languages are mostly used in artificial intelligence research.
Examples of fifth generation languages include Prolog and Mercury.

2. NATURAL LANGUAGE

Natural Language programming aims to use natural language such as
English to write a program.

Instead of using a specific programming language syntax, natural language
programming will use normal English as the input to program software.

Such a technique would mean less technical programming knowledge
is required to write a program.
The programmer needs to define the program using normal language.

3. OPENGL (GRAPHIC LIBRARY)

OpenGL (Graphics Library) is a standard specification to describe the standard Application Programming Interface (API) for 3D/2D computer graphic applications.

OpenGL specification describes a set of functions and the exact behaviours that the 3D/2D application must perform.
OpenGL was developed by Silicon Graphics.

OpenGL is widely used in virtual reality, scientific visualisation, flight simulation and video game development.

OPEN SOURCE..

Open Source

What is Free Software? What is Open Source?

Free Software, refers to software distributed in source form which can be freely modified and redistributed, or freely modifiable and redistributable software. It does not refer to zero-cost software. This usage of the name "Free Software" was common in the Unix world and recently introduced to the general computer community. Free Software is also referred to as Freed Software, Liberated Software (software libre) or FRS (freely redistributable software). "Open Source" is a marketing name for Free Software, coined in Feb 1998 as an attempt to overcome the confusion over the word "free" in the English language. Open Source refers to the fact that the source code of Free Software is open to and for the world to take, to modify and to reuse. The precise meaning of Free Software is spelled out in the Debian Free Software Guidelines or the Free Software Definition while Open Source is defined officially by the Open Source Definition. Open Source and Free Software refer to, originally the same (around Feb 1998), but now different but largely similiar, set of software, but they emphasize different rationals; see Why ``Free Software'' is better than ``Open Source'' for more explanation. Example:Operating Systems -Linux (or GNU/Linux) -FreeBSD -OpenBSD Example:Web Browsers -Mozilla (Netscape 6) Example:Office Suites -Open Office -KOffice

What is Open Sources

1. Free Redistribution The license shall not restrict any party from selling or giving away the software as a component of an aggregate software distribution containing programs from several different sources. The license shall not require a royalty or other fee for such sale. 2. Source Code The program must include source code, and must allow distribution in source code as well as compiled form. Where some form of a product is not distributed with source code, there must be a well-publicized means of obtaining the source code for no more than a reasonable reproduction cost preferably, downloading via the Internet without charge. The source code must be the preferred form in which a programmer would modify the program. Deliberately obfuscated source code is not allowed. Intermediate forms such as the output of a preprocessor or translator are not allowed. 3. Derived Works The license must allow modifications and derived works, and must allow them to be distributed under the same terms as the license of the original software. 4. Integrity of The Author's Source Code The license may restrict source-code from being distributed in modified form only if the license allows the distribution of "patch files" with the source code for the purpose of modifying the program at build time. The license must explicitly permit distribution of software built from modified source code. The license may require derived works to carry a different name or version number from the original software. 5. No Discrimination Against Persons or Groups The license must not discriminate against any person or group of persons. 6. No Discrimination Against Fields of Endeavor The license must not restrict anyone from making use of the program in a specific field of endeavor. For example, it may not restrict the program from being used in a business, or from being used for genetic research. 7. Distribution of License The rights attached to the program must apply to all to whom the program is redistributed without the need for execution of an additional license by those parties. 8. License Must Not Be Specific to a Product The rights attached to the program must not depend on the program's being part of a particular software distribution. If the program is extracted from that distribution and used or distributed within the terms of the program's license, all parties to whom the program is redistributed should have the same rights as those that are granted in conjunction with the original software distribution. 9. License Must Not Restrict Other Software The license must not place restrictions on other software that is distributed along with the licensed software. For example, the license must not insist that all other programs distributed on the same medium must be open-source software. 10. License Must Be Technology-Neutral No provision of the license may be predicated on any individual technology or style of interface.