Video Conferencing

What is Video Conferencing  ???


Video Conferencing is conducting a conference between two or more participants at different sites by using computer network to transmit audio and video data. For example, a point-to-point (two-person) video conferencing system works much like a video telephone. Each participant has a video camera, microphone, and speakers mounted on his or her computer. As the two participants speak to one another, their voices are carried over the network and delivered to the other's speakers, and whatever images appear in front of the video camera appear in a window on the other participant's monitor.

Multipoint videoconferencing allows three or more participants to sit in a virtual conference room and communicate as if they were sitting right next to each other. Until the mid 90s, the hardware costs made videoconferencing prohibitively expensive for most organizations, but that situation is changing rapidly. Many analysts believe that videoconferencing will be one of the fastest growing segments of the computer industry in the latter half of the decade. 

Advantage Video Conferencing

There are many advantages to video conferences:

1. Companies are able to have meetings easily between branches that are situated very far away.
2. Companies are able to save on travel and hotel costs, previously incurred through transporting different employees to one place.
3. Meetings can be organised at short notice.
4. Employees are able to work from home, increasing work flexibility.
5. Meetings do not require large room facilities. 

Disadvantages of Video Conferencing

The disadvantages of Video Conferencing are :

1.Technology can fail or systems may crash/go off-line.

2.Have to give extra training to use the Equipment.

3.Need to employ somebody to set up and maintain Equipment.

4.Time zones may be different if conferencing in different parts of the world.

Type of Video Conferencing

There are three ways for you to set up a video conference:

• computer based system

• desktop system

• studio based system  

VIDEO CONFERENCING ETTHIQUE

IP ADDRESS

INTERNET PROTOCOL ADDRESS
This number is an exclusive number all information technology devices (printers, routers, modems, et al) use which identifies and allows them the ability to communicate with each other on a computer network. There is a standard of communication which is called an Internet Protocol standard. In laymans terms it is the same as your home address. 

In order for you to receive snail mail at home the sending party must have your correct mailing address (IP address) in your town (network) or you do not receive bills, pizza coupons or your tax refund. The same is true for all equipment on the internet. Without this specific address, information cannot be received. IP addresses may either be assigned permanently for an Email server/Business server or a permanent home resident or temporarily, from a pool of available addresses (first come first serve) from your Internet Service Provider. A permanent number may not be available in all areas and may cost extra so be sure to ask your ISP.

DOMAIN NAME SYSTEM (DNS)

This allows the IP address to be translated to words. It is much easier for us to remember a word than a series of numbers. The same is true for email addresses.

For example, it is much easier for you to remember a web address name such as whatismyip.com than it is to remember 192.168.1.1 or in the case of email it is much easier to remember email@somedomain.com than email@192.168.1.1.

DYNAMIC IP ADDRESS

One that is not static and could change at any time. This type is issued to you from a pool of addresses allocated by your ISP or DHCP Server. This is for a large number of customers that do not require the same address all the time for a variety of reasons. Your computer will automatically get this number as it logs on to the network and saves you the trouble of having to know details regarding the specific network configurations. This number can be assigned to anyone using a dial-up connection, Wireless and High Speed Internet connections. If you need to run your own email server or web server, it would be best to have a static IP address.

STATIC IP ADDRESS

One that is fixed and never changes. This is in contrast to a dynamic IP address which may change at any time. Most ISP's can offer to assign a single static IP or a block of static IP's for a few extra bucks a month and may require you upgrading to a business account.

IPv4

Currently used by most network devices. However, with more and more computers accessing the internet, IPv4 IPs are running out quickly. Just like in a city, addresses have to be created for new neighborhoods but, if your neighborhood gets too large, you will have to come up with an entire new pool of addresses. IPv4 is limited to 4,294,967,296 IPs.

IPv5

This is an experimental protocol for UNIX based systems. In keeping with standard UNIX (a computer Operating System) release conventions, all odd-numbered versions are considered experimental. It was never intended to be used by the general public.

IPv6

The replacement for the aging IPv4. The estimated number of unique IPs for IPv6 is 340,282,366,920,938,463,463,374,607,431,768,211,456 or 2^128.

The old and current standard of IPs was this: 192.168.100.100 the new way can be written different ways but means the same and are all valid.

ASYNCHRONOUS VS SYNCHRONOUS

Synchronous and asynchronous transmissions are two different methods of transmission synchronization. 
Synchronous transmissions are synchronized by an external clock, while asynchronous transmissions are synchronized by special signals along the transmission medium.

The send, receive, and reply operations may be synchronous or asynchronous. A synchronous operation blocks a process till the operation completes. An asynchronous operation is non-blocking and only initiates the operation. The caller could discover completion by some other mechanism discussed later. 

The notion of synchronous operations requires an understanding of what it means for an operation to complete. In the case of remote assignment, both the send and receive complete when the message has been delivered to the receiver. In the case of remote procedure call, the send, receive, and reply complete when the result has been delivered to the sender, assuming there is a return value. Otherwise, the send and receive complete when the procedure finishes execution. During the time the procedure is executing, the sender and receiver are in a rendezvous, as mentioned before.

Note that synchronous/asynchronous implies blocking/not blocking but not vice versa, that is, not every blocking operation is synchronous and not every non blocking operation is asynchronous. For instance, a send that blocks till the receiver machine has received the message is blocking but not synchronous since the receiver process may not have received it. Similarly, we will see later a Xinu receive that is non-blocking but is not asynchronous. These definitions of synchronous/asynchronous operations are similar but not identical to the ones given in your text books, which tend to equate synchronous with blocking.

Asynchronous message passing allows more parallelism. Since a process does not block, it can do some computation while the message is in transit. In the case of receive, this means a process can express its interest in receving messages on multiple ports simultaneously. (The select primitive discussed later provides this facility for synchronous receives). In a synchronous system, such parallelism can be achieved by forking a separate process for each concurrent operation, but this approach incurs the cost of extra process management. This cost is typically bearable with lwps but not hwps.

Asynchronous message passing introduces several problems. What happens if a message cannot be delivered? The sender may never wait for delivery of the message, and thus never hear about the error. Similarly, a mechanism is needed to notify an asynchronous receiver that a message has arrived. The operation invoker could learn about completion/errors by polling, getting a software interrupt, or by waiting explicitly for completion later using a special sycnhronous wait call. An asynchronous operation needs to return a call/transaction id if the application needs to be later notified about the operation. At notification time, this id would be placed in some global location or passed as an argument to a handler or wait call.

Another problem related to asynchronous message passing has to do with buffering. If messages sent asynchronously are buffered in a space managed by the OS, then a process may fill this space by flooding the system with a large number of messages. 

NETWORK HARDWARE

Networking hardware or networking equipment typically refers to devices facilitating the use of a computer network. Typically, this includes gateways, routers, network bridges, switches, hubs, and repeaters. Also, hybrid network devices such as multilayer switches, protocol converters and bridge routers. And, proxy servers, firewalls and network address translators. Also, multiplexers,network interface controllers, wireless network interface controllers, modems, ISDN terminal adapters and line drivers. And, wireless access points, networking cables and other related hardware.

Computer networking devices are units that mediate data in a computer network.[1][2] Computer networking devices are also called network equipment, Intermediate Systems (IS)[citation needed] or InterWorking Unit (IWU).[citation needed] Units which are the last receiver or generate data are called hosts or data terminal equipment.[citation needed]

The most common kind of networking hardware today is copper-based Ethernet adapters, helped largely by its standard inclusion on most modern computer systems. Wireless networking has become increasingly popular, however, especially for portable and handheld devices.

Other hardware prevalent within computer networking is datacenter equipment (such as file servers, database servers and storage areas), network services (such as DNS, DHCP, email etc) as well as other specific network devices such as content delivery.

Other diverse devices which may be considered networking hardware include mobile phones, PDAs and even modern coffee machines. As technology grows and IP-based networks are integrated into building infrastructure and household utilities, network hardware becomes an ambiguous statement owing to the increasing number of "network capable" endpoints.

Computer Networking Devices

File 0r Network Server

One or more network servers is a part of nearly every local area network.These are very fast computers with a large amount of RAM and storage space, along with a one or more fast network interface card(s). The network operating system provides tools to share server resources and information with network users. A sophisticated permissions-handling system is included, so that access to sensitive information can be carefully tailored to the needs of the users. For small networks, a singe network server may provide access control, file sharing, printer sharing, email, database, and other services.

The network server may be responding to requests from many network users simultaneously. For example, it may be asked to load a word processor program to one workstation, receive a database file from another workstation, and store an e-mail message during the same time period. This requires a computer that can store and quickly share large amounts of information. When configuring such a server, budget is usually the controlling factor. The following guidelines should be followed:

• Fastest processor(s)
• Large amount of RAM
• multiple large, fast hard drives
• Extra expansion slots
• Fast network interface card(s)

Workstations

Computers that humans use are broadly categorized as workstations. A typical workstation is a computer that is configured with a network interface card, networking software, and the appropriate cables. Workstations do not necessarily need large storage hard drives, because files can be saved on the file server. Almost any computer can serve as a network workstation.

Network Interface Card

The network interface card (NIC) provides the physical connection between the network and the computer workstation. Most NICs are internal, and they are included in the purchase of most computers. Network interface cards are a major factor in determining the speed and performance of a network. It is a good idea to use the fastest network card available for the type of workstation you are using.

The most common network interface connections are Ethernet cards and wireless adapters.

Ethernet Card

Ethernet cards are usually included with a computer, although additional ethernet cards can be purchased and installed on most computers,. Ethernet cards can contain connections for either coaxial or twisted pair cables (or both) (See fig. 1). If it is designed for coaxial cable, the connection will be BNC. If it is designed for twisted pair, it will have a RJ-45 connection. Some Ethernet cards also contain an AUI connector. This can be used to attach coaxial, twisted pair, or fiber optics cable to an Ethernet card. When this method is used there is always an external transceiver attached to the workstation. Only the RJ-45 connector is found on most modern ethernet cards.

An ethernet switch is a device that provides a central connection point for cables from workstations, servers, and peripherals. In a star topology, twisted-pair wire is run from each workstation to a central switch/hub. Most switches are active, that is they electrically amplify the signal as it moves from one device to another. The predecessor of the switch was the hub, which broadcasted all inbound packets out all ports of the device, creating huge amounts of unnecessary network traffic. Modern switches build a port map of all IP address which respond on each port, and only broadcasts on all ports when it doesn't have a packet's target IP address already in its port map. Switches are:
Usually configured with 8, 12, or 24 RJ-45 ports
Often used in a star or tree topology
Available as "managed" or "unmanaged", with the later less expensive, but adequate for smaller networks
direct replacements for hubs, immediately reducing network traffic in most networks
Usually installed in a standardized metal rack that also may store network servers, bridges, or routers


An ethernet switch is a device that provides a central connection point for cables from workstations, servers, and peripherals. In a star topology, twisted-pair wire is run from each workstation to a central switch/hub. Most switches are active, that is they electrically amplify the signal as it moves from one device to another. The predecessor of the switch was the hub, which broadcasted all inbound packets out all ports of the device, creating huge amounts of unnecessary network traffic. Modern switches build a port map of all IP address which respond on each port, and only broadcasts on all ports when it doesn't have a packet's target IP address already in its port map. Switches are:

 -Usually configured with 8, 12, or 24 RJ-45 ports 
-Often used in a star or tree topology
-Available as "managed" or "unmanaged", with the later less expensive, but adequate for -smaller networks
-direct replacements for hubs, immediately reducing network traffic in most networks
-Usually installed in a standardized metal rack that also may store network servers, bridges, or routers

Ethernet Card

Switches

An ethernet switch is a device that provides a central connection point for cables from workstations, servers, and peripherals. In a star topology, twisted-pair wire is run from each workstation to a central switch/hub. Most switches are active, that is they electrically amplify the signal as it moves from one device to another. The predecessor of the switch was the hub, which broadcasted all inbound packets out all ports of the device, creating huge amounts of unnecessary network traffic. Modern switches build a port map of all IP address which respond on each port, and only broadcasts on all ports when it doesn't have a packet's target IP address already in its port map. Switches are:

• Usually configured with 8, 12, or 24 RJ-45 ports
• Often used in a star or tree topology
• Available as "managed" or "unmanaged", with the later less expensive, but adequate for smaller networks
• direct replacements for hubs, immediately reducing network traffic in most networks
• Usually installed in a standardized metal rack that also may store network servers, bridges, or routers

Repeaters

Since a signal loses strength as it passes along a cable, it is often necessary to boost the signal with a device called a repeater. The repeater electrically amplifies the signal it receives and rebroadcasts it. Repeaters can be separate devices or they can be incorporated into a concentrator. They are used when the total length of your network cable exceeds the standards set for the type of cable being used.

A good example of the use of repeaters would be in a local area network using a star topology with unshielded twisted-pair cabling. The length limit for unshielded twisted-pair cable is 100 meters. The most common configuration is for each workstation to be connected by twisted-pair cable to a multi-port active concentrator. The concentrator amplifies all the signals that pass through it allowing for the total length of cable on the network to exceed the 100 meter limit.

Repeaters

Bridges

A bridge is a device that allows you to segment a large network into two smaller, more efficient networks. If you are adding to an older wiring scheme and want the new network to be up-to-date, a bridge can connect the two.

A bridge monitors the information traffic on both sides of the network so that it can pass packets of information to the correct location. Most bridges can "listen" to the network and automatically figure out the address of each computer on both sides of the bridge. The bridge can inspect each message and, if necessary, broadcast it on the other side of the network.

The bridge manages the traffic to maintain optimum performance on both sides of the network. You might say that the bridge is like a traffic cop at a busy intersection during rush hour. It keeps information flowing on both sides of the network, but it does not allow unnecessary traffic through. Bridges can be used to connect different types of cabling, or physical topologies. They must, however, be used between networks with the same protocol.

Routers

Routers are the traffic directors of the global internet. All routers maintain complex routing tables which allow them to determine appropriate paths for packets destined for any address. Routers communicate with each other, and forward network packets out of or into a network. Here's an example:

You want to search for something on the internet using a search engine. You open a browser on your workstation. The browser opens to a blank page (not usually the default, but appropriate for this example). You type "http://www.google.com" into the URL (Universal Resource Locator) address line of the browser. The browser software packages up the URL you typed, and sends it with a request for an IP address to the DNS (Domain Name Server) that has been set in your network adapter's configuration. The domain server returns an IP, such as 74.125.67.103 (actual address returned by DNS for google.com on June 7th, 2011). The browser ships the request for that IP address off to the network card, which bundles the request into an ethernet packet, destined for 74.125.67.103. The network card sends the packet to the gateway of your network, which opens the header of the packet, and makes a determination that the packet is traveling out of your network, in search of 74.125.67.103. Your network's router has routing tables which it has been building from communicating with other routers, and potentially augmented with "static routes", which are specific paths added by your network's administrators to make the task of accessing certain networks easier, or faster, or in some cases, not possible. In this case, I find that my router knows about another router at my ISP(Internet Service Provider), which in turn has several more routers that are all on networks of which I am just a small node, much like finding an atom of a molecule of a piece of dust on a rock on a moon of a planet of a sun of a galaxy of the universe. In any case, the packet gets passed from router to router, each time moving out of the subnets of the packet sender, towards a router that will know where the desired server is. The packet finally reaches the router of the network at 74.125.67.103, which dutifully delivers the packet to the server at that IP address. The server carefully crafts a response, and sends a reply back, which follows the same process to get the response "Yes. Go ahead" back to the requester. Whew. And that's just the initial request.

While bridges know the addresses of all computers on each side of the network, routers know the addresses other routers which in turn know about their own networks. Routers can even "listen" to entire networks to determine which sections are busiest -- they can then redirect data around those sections until traffic congestion clears.

So, routers are network gateways. They move network packets from one network to another, and many can convert from one network protocol to another as necessary. Routers select the best path to route a message, based on the destination address of the packet. The router can direct traffic to prevent head-on collisions, and is smart enough to know when to direct traffic along back roads and shortcuts.

If you have a school LAN that you want to connect to the Internet, you will need to purchase a router. In this case, the router serves as the forwarder between the information on your LAN and the Internet. It also determines the best route to send the data over the Internet.

Routers

COMPUTER

Today, I want to discuss we all of you about COMPUTER.First of all,what is Computer?For sure most of you what computer it is.Computer is something that can less human energy and something that easier for man kind to settle down their project or work.
However,the truth definition of computer is :
A system of interconnected computers that share a central storage system and various peripheral devices such as a printers, scanners, or routers. Each computer connected to the system can operate independently, but has the ability to communicate with other external devices and computers.

Parts Of Computer

If you use a desktop computer, you might already know that there isn't any single part called the "computer." A computer is really a system of many parts working together. The physical parts, which you can see and touch, are collectively called hardware. (Software, on the other hand, refers to the instructions, or programs, that tell the hardware what to do.)

The illustration below shows the most common hardware in a desktop computer system. Your system may look a little different, but it probably has most of these parts. A laptop computer has similar parts but combines them into a single notebook-sized package.

System Unit

The system unit is the core of a computer system. Usually it's a rectangular box placed on or underneath your desk. Inside this box are many electronic components that process information. The most important of these components is the central processing unit (CPU), or microprocessor, which acts as the "brain" of your computer. Another component israndom access memory (RAM), which temporarily stores information that the CPU uses while the computer is on. The information stored in RAM is erased when the computer is turned off.

Almost every other part of your computer connects to the system unit using cables. The cables plug into specific ports (openings), typically on the back of the system unit. Hardware that is not part of the system unit is sometimes called a peripheral device ordevice.

Keyboard

A keyboard is used mainly for typing text into your computer. Like the keyboard on a typewriter, it has keys for letters and numbers, but it also has special keys:

• The function keys, found on the top row, perform different functions depending on where they are used.
• The numeric keypad, located on the right side of most keyboards, allows you to enter numbers quickly.
• The navigation keys, such as the arrow keys, allow you to move your position within a document or webpage.

Monitor

A monitor displays information in visual form, using text and graphics. The portion of the monitor that displays the information is called the screen. Like a television screen, a computer screen can show still or moving pictures.

There are two basic types of monitors: CRT (cathode ray tube) monitors and LCD (liquid crystal display) monitors. Both types produce sharp images, but LCD monitors have the advantage of being much thinner and lighter. CRT monitors, however, are generally more affordable.

Speakers

Speakers are used to play sound. They may be built into the system unit or connected with cables. Speakers allow you to listen to music and hear sound effects from your computer.

Spam???. Awas !!

Apa Itu SPAM?

Spam ini sebenarnya sudah banyak kita jumpai di kehidupan sehari-hari. Pernahkah Anda ketika keluar dari rumah ada brosur yang bertumpuk di depan pintu depan rumah Anda? Entah brosur itu dari mana, tentang penawaran apa, yang kirimnya siapa, dll. Atau mungkin Anda pernah juga melihat sebuah iklan yang menempel di pintu mobil angkot. Nah, aktifitas seperti inilah yang disebut SPAM alias iklan yang tanpa dikehendaki oleh si penerima.

Sebagai gambaran lagi, misalkan Anda menerima email dari sebuah email yang sebelumnya tanpa Anda kenal yang isinya berupa penawaran sebuah produk atau jasa, maka itupun disebut SPAM. Bukan hanya di email, tapi melalui SMS pun itu dikatakan SPAM. Misalkan ada sebuah nomor yang tak dikenal, tanpa ada hubungan APA PUN sebelumnya, mengirim sebuah pesan yang berbau promosi…
Contoh sederhana lain dari SPAM:

Pada email : Kadang-kadang kita menerima email-email yang tidak kita inginkan di Inbox yang berisi iklan-iklan yang pengirimnya gak jelas,
Pada blog, kita mendapati link-link iklan pada kolom komentar dan link-link itu menyuruh si pemilik Blog/orang yang membacanya menuju link tersebut, jadi si tukang SPAM ini sama sekali tidak menanggapi “isi dari tulisan kita” (keterlaluan kan?)
Pada ShoutBox, Hanya menyuruh kita ke link-link aneh, dan si tukang SPAM ini tidak menunjukkan jati dirinya…

HACKER

Pernah menjadi satu isu tentang ANONYMOUS dimana mereka telah menggodam laman web kerajaan,blog,email, dan bermacam lagi yang berlaku pada tahun lepas. Dan sudah tentu la apabila ia melibatkan malaysia yang menggodamnya mesti  Anonymous Malaysia.

Tahukah apa itu hacker atau penggodam??


Penggodam (hacker) dalam konteks keselamatan komputer merujuk kepada penggodam komputer yang terlibat dalam keselamatan komputer dan berupaya mengeksploit sistem atau masuk tanpa kebenaran melalui kemahiran, taktik dan pengetahuan terperinci.
Dalam penggunaan biasa, "penggodam" merujuk kepada penggodam topi hitam (penggodam berniat jahat atau jenayah). Terdapat juga penggodam beretika (biasanya digelar topi putih) dan penggodam yang samar-samar kedudukannya (topi kelabu).

ISTILAH :


Penggodam (hacker) boleh membawa maksud seseorang yang mahir dalam bidang komputer; namun media massa selalu menyamakan "penggodam" dengan "penggodam topi hitam".


Topi hitam (black hat): seseorang yang mensubversi keselamatan komputer tanpa izin atau menggunakan teknologi (biasanya sebuah komputer ataupun internet) untuk tujuan keganasan, vandalisme, penipuan kad kredit, pencurian identiti, pencurian hak milik intelektual, dan sebagainya. Ini juga bermakna mengambil alih kawalan komputer lain melalui sebuah rangkaian, atau perekahan perisian (software cracking).


Topi kelabu (grey hat): Penggodam yang etikanya tidak jelas atau di batasan undang-undang, seringkali mengaku terang-terang.


Topi putih (white hat): Penggodam beretika yang memecah keselamatan tetapi untuk tujuan altruistik ataupun sekurang-kurangnya tidak berniat jahat. Topi putih biasanya mempunyai etika yang jelas, dan selalu berusaha untuk bekerja dengan pengilang atau pemilik untuk memperbaiki kelemahan yang dijumpai, walaupun banyak yang mengancam sama ada tersirat atau jelas untuk memaklumkan kepada awam selepas tempoh "sesuai" untuk memastikan respons yang kena pada waktunya. Istilah ini juga digunakan untuk penggodam yang mereka dan mengekod sistem yang lebih selamat.


Perekah/Penggertak (cracker):
Topi hitam. Sering digunakan untuk membezakan penggodam topi hitam dengan penggodam lain.
Penggodam komputer yang menggunakan perekahan kata laluan atau serangan kuasa keras. Berkait denga istilah pemecah peti besi.
Perekah perisian. Orang yang mengkhusus dalam mengatasi mekanisma perlindungan penyalinan perisian. Tidak mengeksploit rangkaian, cuma perisian.


Budak skrip (script kiddie): Penceroboh komputer yang tidak begitu mahir; seseorang yang sekadar mengikut arahan ataupun menggunakan teknik buku resepi tanpa memahami langkah yang dibuatnya. Pejoratif.

Hacktivis merupakan penggodam aktivis yang menggunakan teknologi untuk mengumumkan pesanan politik. Perlu dicatat bahawa vandalisme web bukan semestinya hacktivisme.

RAM

RAM (random access memory) is the place in a computer where the operating system, application programs, and data in current use are kept so that they can be quickly reached by the computer's processor. RAM is much faster to read from and write to than the other kinds of storage in a computer, the hard disk, floppy disk, and CD-ROM. However, the data in RAM stays there only as long as your computer is running. When you turn the computer off, RAM loses its data. When you turn your computer on again, your operating system and other files are once again loaded into RAM, usually from your hard disk.

RAM can be compared to a person's short-term memory and the hard disk to the long-term memory. The short-term memory focuses on work at hand, but can only keep so many facts in view at one time. If short-term memory fills up, your brain sometimes is able to refresh it from facts stored in long-term memory. A computer also works this way. If RAM fills up, the processor needs to continually go to the hard disk to overlay old data in RAM with new, slowing down the computer's operation. Unlike the hard disk which can become completely full of data so that it won't accept any more, RAM never runs out of memory. It keeps operating, but much more slowly than you may want it to.

How Big is RAM?

RAM is small, both in physical size (it's stored in microchips) and in the amount of data it can hold. It's much smaller than your hard disk. A typical computer may come with 256 million bytes of RAM and a hard disk that can hold 40 billion bytes. RAM comes in the form of "discrete" (meaning separate) microchips and also in the form of modules that plug into holes in the computer's motherboard. These holes connect through a bus or set of electrical paths to the processor. The hard drive, on the other hand, stores data on a magnetized surface that looks like a phonograph record.

Most personal computers are designed to allow you to add additional RAM modules up to a certain limit. Having more RAM in your computer reduces the number of times that the computer processor has to read data in from your hard disk, an operation that takes much longer than reading data from RAM. (RAM access time is in nanoseconds; hard disk access time is in milliseconds.)

Why Random Access?

RAM is called "random access" because any storage location can be accessed directly. Originally, the term distinguished regular core memory from offline memory, usually on magnetic tape in which an item of data could only be accessed by starting from the beginning of the tape and finding an address sequentially. Perhaps it should have been called "nonsequential memory" because RAM access is hardly random. RAM is organized and controlled in a way that enables data to be stored and retrieved directly to specific locations. Note that other forms of storage such as the hard disk and CD-ROM are also accessed directly (or "randomly") but the term random access is not applied to these forms of storage.

In addition to disk, floppy disk, and CD-ROM storage, another important form of storage is read-only memory (ROM), a more expensive kind of memory that retains data even when the computer is turned off. Every computer comes with a small amount of ROM that holds just enough programming so that the operating system can be loaded into RAM each time the computer is turned on.

Tips to Combat Viruses, Worms and Trojan Horses on Your Computer

Tips to Combat Viruses, Worms and Trojan Horses on Your Computer

Keep The Operating System Updated

The first step in protecting your computer from any malicious there is to ensure that your operating system (OS) is up-to-date. This is essential if you are running a Microsoft Windows OS. Secondly, you need to have anti-virus software installed on your system and ensure you download updates frequently to ensure your software has the latest fixes for new viruses, worms, and Trojan horses. Additionally, you want to make sure your anti-virus program has the capability to scan e-mail and files as they are downloaded from the Internet, and you also need to run full disk scans periodically. This will help prevent malicious programs from even reaching your computer.

Use a Firewall

You should also install a firewall. A firewall is a system that prevents unauthorized use and access to your computer. A firewall can be either hardware or software. Hardware firewalls provide a strong degree of protection from most forms of attack coming from the outside world and can be purchased as a stand-alone product or in broadband routers. Unfortunately, when battling viruses, worms and Trojans, a hardware firewall may be less effective than a software firewall, as it could possibly ignore embedded worms in out going e-mails and see this as regular network traffic.

For individual home users, the most popular firewall choice is a software firewall.  A good software firewall will protect your computer from outside attempts to control or gain access your computer, and usually provides additional protection against the most common Trojan programs or e-mail worms. The downside to software firewalls is that they will only protect the computer they are installed on, not a network.

It is important to remember that on its own a firewall is not going to rid you of your computer virus problems, but when used in conjunction with regular operating system updates and a good anti-virus scanning software, it will add some extra security and protection for your computer or network. 

Did You Know... CodeRed, a blended threat, launched DoS attacks, defaced Web servers, and its variant, CodeRed II, left Trojan horses behind for later execution. CodeRed was processed in memory — not on a hard disk — allowing it to slip past some anti-virus products. Computer Economics has estimated the worldwide cost of CodeRed at $2.62 billion dollars. [Source:Symantec Web site]

Data Transmission Modes

Data Transmission Modes

Data Transmission Modes

There are three ways for transmitting data from one point to another.

1. Simplex : In simplex mode the communication can take place in one

direction. The receiver receives the signal from the transmitting device.

In this mode the flow of information is Uni-directional. Hence it is rarely

used for data communication.

2. Half-duplex : In half-duplex mode the communication channel is used

in both directions, but only in one direction at a time. Thus a half-duplex

line can alternately send and receive data.

3. Full-duplex : In full duplex the communication channel is used in both

directions at the same time. Use of full-duplex line improves the

efficiency as the line turnaround time required in half-duplex arrangement

is eliminated. Example of this mode of transmission is the telephone

line.