الصفحات

Thursday, December 27, 2012

What is multimedia?

Multimedia  

The  word  multimedia  is  composed  of  two  parts:  the  prefix  multi  and  media.
Multi = Plural, more than 1, many
Media = Medium of communication


Definition:
Multimedia is the presentation of a computer application incorporating media elements such as text, graphics, animations, audio, and video.



Classification of media types
Classification of media types


Characteristics of Multimedia System
They  must  be  computer-controlled. User is able to view, hear, and see using a Multimedia PC System.

They  are  integrated. At least one discrete and one continuous media combined for information presentation and sharing.

The information  they  handle  must  be  represented digitally.

The  interface  to  the  final  user may  permit  interactivity. User is able to navigate, interact, create, and communicate.


Benefits of using multimedia in software
* Ease of use
        User friendly, increase user’s effectiveness
*Intuitive Interface
        Allows user to determine functions of an application by their own intuition
*Immersive Experience
         Software application takes over the entire computer screen, allows user to focus on application 
*Self-paced interaction & better retention
         allows information processing at one’s own pace.
*Better understanding
         simultaneous presentation of different media provides richer & broader range of information.
*Cost effectiveness
          less training, less technical support


Problems with Multimedia 
Investment costs
- multimedia involves high volume of content
- expensive copyright and royalty
Technical barriers (accessibility issues)
- upgrade IT & PC infrastructure
Legal problems 
        - Copyright

Where to use multimedia ?
  • Business
  • Government
  • Education
  • Broadcasting & Entertainment
  • Research & Development
  • Health

more... Résuméabuiyad

Monday, December 24, 2012

What are Viruses ?


Viruses 

Viruses is piece of software that infects programs include:


  • modifies them to include a copy of the virus
  • replicates and goes on to infect other content
  • easily spread through network environments

when attached to an executable program a virus can do anything that the program is permitted to do like:
  • executes secretly when the host program is run


Virus Components :
infection mechanism
means by which a virus spreads or propagates
also referred to as the infection vector

trigger
event or condition that determines when the payload is activated or delivered
sometimes known as a logic bomb

payload
what the virus does (besides spreading)
may involve damage or benign but noticeable activity

Virus Phases
dormant phase
virus is idle
will eventually be activated by some event
not all viruses have this stage

triggering phase
virus is activated to perform the function for which it was intended
can be caused by a variety of system events

propagation phase
virus places a copy of itself into other programs or into certain system areas on the disk
may not be identical to the propagating version
each infected program will now contain a clone of the virus which will itself enter a propagation phase

execution phase
function is performed
may be harmless or damaging

Virus Classifications
we can classification virus by target or by strategy
1-classification by target
boot sector infector
infects a master boot record or boot record and spreads when a system is booted from the disk  containing the virus
file infector 
infects files that the operating system or shell considers to be executable
macro virus
infects files with macro or scripting code that is interpreted by an application
multipartite virus
infects files in multiple ways


2-classification by concealment strategy

encrypted virus
a portion of the virus creates a random encryption key and encrypts the remainder of the virus
stealth virus
a form of virus explicitly designed to hide itself from detection by anti-virus software
polymorphic virus
a virus that mutates with every infection
metamorphic virus
a virus that mutates and rewrites itself completely at each iteration and may change behavior as well as appearance

.........................................................
follow us in facebook and twitter:
more... Résuméabuiyad

Friday, December 21, 2012

History of the Internet | part3


You can see History of Internet part 1 : Here
You can see History of Internet part 2 : Here

In 1986, the National Science Foundation funded NSFNet as a cross country 56 Kbps backbone for the Internet. They maintained their sponsorship for nearly a decade, setting rules for its non-commercial government and research uses. 
Between the beginning of 1986 and the end of 1987 the number of networks grows from 2,000 to nearly 30,000.

As the commands for e-mail, FTP, and telnet were standardized, it became a lot easier for non-technical people to learn to use the nets. It was not easy by today's standards by any means, but it did open up use of the Internet to many more people in universities in particular. 

Other departments besides the libraries, computer, physics, and engineering departments found ways to make good use of the nets--to communicate with colleagues around the world and to share files and resources. 

In 1989 another significant event took place in making the nets easier to use. Tim Berners-Lee and others at the European Laboratory for Particle Physics, more popularly known as CERN, proposed a new protocol for information distribution. This protocol, which became the World Wide Web in 1991, was based on hypertext--a system of embedding links in text to link to other text, which you have been using every time you selected a text link while browsing the internet.

Since the Internet was initially funded by the government, it was originally limited to research, education, and government uses. Commercial uses were prohibited unless they directly served the goals of research and education. This policy continued until the early 90's, when independent commercial networks began to grow. 

It then became possible to route traffic across the country from one commercial site to another without passing through the government funded NSFNet Internet backbone. 
Delphi was the first national commercial online service to offer Internet access to its subscribers. It opened up an email connection in July 1992 and full Internet service in November 1992. 

Microsoft's full scale entry into the browser, server, and Internet Service Provider market completed the major shift over to a commercially based Internet. The release of Windows 98 in June 1998 with the Microsoft browser well integrated into the desktop shows Bill Gates' determination to capitalize on the enormous growth of the Internet. 

A current trend with major implications for the future is the growth of high speed connections. 56K modems and the providers who supported them spread widely for a while, but this is the low end now. 56K is not fast enough to carry multimedia, such as sound and video except in low quality. 

But new technologies many times faster, such as cablemodems and digital subscriber lines (DSL) are predominant now.
Wireless has grown rapidly in the past few years, and travellers search for the wi-fi "hot spots" where they can connect while they are away from the home or office. Many airports, coffee bars, hotels and motels now routinely provide these services, some for a fee and some for free. 
The next big growth area is the surge towards universal wireless access, where almost everywhere is a "hot spot".


more... Résuméabuiyad

History of the Internet | part2



You can see History of Internet part 1 : HERE

Who was the first to use the Internet?
Charley Kline at UCLA sent the first packets on ARPANet as he tried to connect to Stanford Research Institute on Oct 29, 1969. The system crashed as he reached the G in LOGIN!

The Internet was designed in part to provide a communications network that would work even if some of the sites were destroyed by nuclear attack. If the most direct route was not available, routers would direct traffic around the network via alternate routes.

The early Internet was used by computer experts, engineers, scientists, and librarians. There was nothing friendly about it. There were no home or office personal computers in those days, and anyone who used it, whether a computer professional or an engineer or scientist or librarian, had to learn to use a very complex system. 

E-mail was adapted for ARPANET by Ray Tomlinson of BBN in 1972. He developed the “user@host” convention and picked the @ symbol from the available symbols on his teletype to link the username and address.  The @ was already in use as an escape character prompt, or command indicator on many other systems.  Not until late 1980’s will the ‘@’ finally become  a worldwide standard.  
The telnet protocol, enabling logging on to a remote computer, was published as a Request for Comments (RFC) in 1972. RFC's are a means of sharing developmental work throughout community. 

The ftp protocol, enabling file transfers between Internet sites, was published as an RFC in 1973, and from then on RFC's were available electronically to anyone who had use of the ftp protocol. 
Libraries began automating and networking their catalogs in the late 1960s independent from ARPA. 

The visionary Frederick G. Kilgour of the Ohio College Library Center (now OCLC, Inc.) led networking of Ohio libraries during the '60s and '70s. In the mid 1970s more regional consortia from New England, the Southwest states, and the Middle Atlantic states, etc., joined with Ohio to form a national, later international, network. Automated catalogs, not very user-friendly at first, became available to the world, first through telnet and only many years later, through the web. 

Ethernet, a protocol for many local networks, appeared in 1974, an outgrowth of Harvard student Bob Metcalfe's dissertation on "Packet Networks." The dissertation was initially rejected by the University for not being analytical enough. It later won acceptance when he added some more equations to it. 

The Internet matured in the 70's as a result of the TCP/IP architecture ( a net-to-net protocol) first proposed by Bob Kahn at BBN and further developed by Kahn and Vint Cerf at Stanford and others throughout the 70's. It was adopted by the Defense Department in 1980 replacing the earlier Network Control Protocol (NCP) and universally adopted by 1983. 

The Unix to Unix Copy Protocol (UUCP) was invented in 1978 at Bell Labs. Usenet was started in 1979 based on UUCP. 
Newsgroups, which are discussion groups focusing on a topic, followed, providing a means of exchanging information throughout the world . 


Usenet is not considered as part of the Internet, since it does not share the use of TCP/IP, it linked UNIX systems around the world, and many Internet sites took advantage of the availability of newsgroups. It was a significant part of the community building that took place on the networks.

Similarly, BITNET (Because It's Time Network) connected IBM mainframes around the educational community and the world to provide mail services beginning in 1981. Listserv software was developed for this network and later others. 

Gateways were developed to connect BITNET with the Internet and allowed exchange of e-mail, particularly for e-mail discussion lists. These listservs and other forms of e-mail discussion lists formed another major element in the community building that was taking place. 

Continue Read History of Internet part 3 

more... Résuméabuiyad

History of the Internet | part1



In this subject you can read the most important note about History of internet

The Internet was the result of some visionary thinking by people in the early 1960’s who saw great potential value in allowing computers to share information on research and development in scientific and military fields.


Licklider of MIT, first proposed a global network of computers in 1962, where everyone in the globe is interconnected and can access programs and data at any site from anywhere.  He moved over to the Defense Advanced Research Projects Agency (DARPA) in late 1962 to head the work to develop it.

Leonard Kleinrock of MIT and later UCLA developed the theory of packet switching, which was to form the basis of Internet connections. 

Lawrence Roberts of MIT connected a Massachusetts computer with a California computer in 1965 over dial-up telephone lines. It showed the feasibility of wide area networking, but also showed that the telephone line's circuit switching was inadequate. 

Kleinrock's packet switching theory was confirmed. Roberts moved over to DARPA in 1966 and developed his plan for ARPANET. 

The Internet, then known as ARPANET, was brought online in 1969 under a contract let by the renamed Advanced Research Projects Agency (ARPA) which initially connected four major computers at universities in the southwestern US (UCLA, Stanford Research Institute, UCSB, and the University of Utah).
After installation in September, handwritten logs from UCLA show the first host-to-host connection, from UCLA to SRI, is made on October 29, 1969 

The contract was carried out by BBN of Cambridge, MA under Bob Kahn and went online in December 1969. 
By June 1970, MIT, Harvard, BBN, and Systems Development Corp (SDC) in Santa Monica, Cal. were added (Nodes are added to ARPANET at the rate of one per month).
By January 1971, Stanford, MIT's Lincoln Labs, Carnegie-Mellon, and Case-Western Reserve U were added. 

In months to come, NASA/Ames, Mitre, Burroughs, RAND, and the U of Illinois plugged in. After that, there were far too many to keep listing here. 


Continue Read History of Internet part 2
more... Résuméabuiyad
;