Distributed system is a non-centralized network consisting of numerous computers that can communicate with one another and that appear to users as parts of a single, large, accessible "storehouse" of shared hardware, software, and data. A distributed system is conceptually the opposite of a centralized, or monolithic, system in which clients connect to a single central computer, such as a mainframe.

In this age of viruses and hackers, of electronic eavesdropping and electronic fraud, security is paramount. Cryptography is the science of providing security for information through the reversible transformation of data. It is a science of great antiquity.The development of digital computing revolutionized cryptography has made today's highly complex and secure cryptographic systems possible.

Network security spans a large number of disciplines, ranging from management and policy topics to operating system kernel fundamentals. Network security revolves around the three key principles of confidentiality, integrity, and availability. Protection of networks and their services from unauthorized modification, destruction, or disclosure, and provision of assurance that the network performs its critical functions correctly and there are no harmful side-effects.

computer architecture is the conceptual design and fundamental operational structure of a computer system. It is a blueprint and functional description of requirements (especially speeds and interconnections) and design implementations for the various parts of a computer — focusing largely on the way by which the central processing unit (CPU) performs internally and accesses addresses in memory.

The arrangement and creation of web pages that in turn make up a web site. There are many aspects to this process, and due to the rapid development of the Internet, new aspects are continually being added. In the beginning, the Web was simple. There was only one browser for viewing web pages and it ran exclusively on the Unix platform. There were about a dozen tags that made any difference. Designing a web page was a relatively simple task.It is n’t so easy anymore. With the explosion of the Web came an avalanche of new technologies, proprietary tags, and acronyms. The biggest challenge now in web design is dealing with the variety of browsers and platforms, each with its own support and implementation of HTML and scripting elements.