Today’s fast growing world needs faster communication. Technology is making rapid progress and is making many things easier. The innovative idea’s that have been emerged from the tender minds of young scientists led to the evolution of many techniques where our present topic ‘MOBILE COMPUTING’ fits in.

 “MOBILE COMPUTING” and COMMUNICATIONS is a major part of wireless communication technology. Mobile computing in means computing done by intermittently connected users who access network resources. It requires a wireless medium such as cellular radio, radio nets and low-orbit satellites. It incorporates wireless adapters using cellular telephone technology to connect portable computers with the cabled network.

Mobile voice communication is widely established throughout the world and had a very rapid increase in the number of subscribers to the various cellular networks over the last few years. An extension of this technology is the ability to send and receive data across these cellular networks. This is the principle of mobile computing.

Mobile data communication has become a very important and rapidly evolving technology as it allows users to transmit data from remote locations to other remote or fixed locations. This proves to be the solution to the biggest problem of business people on the move-mobility. We in this paper describes about the Mobility Services Architecture which supports applications by a middleware stub. Mobile Computing evolved during the last few years as a result of shrinking portables and growing wireless networks. It enlarges the usability of computers, but raises demanding challenges.

The most familiar aspect of mobile computing technology is the hand phone. About two decades ago, a hand phone was bulky and was only used for voice communication. It was merely an extension of the fixed line telephony that allowed users to keep in touch with colleagues. Now the hand phone is not only used for voice communication, it is also used to send text and multimedia messages. Future mobile devices will not only enable Internet access, but will also support high-speed data services.

Mobile computing is a generic term describing one's ability to use technology while moving, as opposed to portable computers, which are only practical for use while deployed in a stationary configuration.

Many types of mobile computers have been introduced since the 1990s, including the:

• Wearable computer

• Personal digital assistant

• Smartphone

• Carputer

• Ultra-Mobile PC

Wearable computers are computers that are worn on the body. This type of wearable technology has been used in behavioral modeling, health monitoring systems, information technologies and media development. Wearable computers are especially useful for applications that require computational support while the user's hands, voice, eyes, arms or attention are actively engaged with the physical environment.

PDA:- A personal digital assistant (PDA) is a mobile device, also known as a palmtop computer. PDAs are used to organize a person's life by taking notes, holding contacts, and connecting to the Internet. Newer PDAs commonly have color screens and audio capabilities, enabling them to be used as mobile phones (smartphones), web browsers, or portable media players. Many PDAs can access the Internet, intranets or extranets via Wi-Fi, or Wireless Wide Area Networks (WWANs). Many PDAs employ touchscreen technology.

A smart phone is a mobile phone offering advanced capabilities, often with PC-like functionality (PC-mobile handset convergence). There is no industry standard definition of a smartphone. For some, a smartphone is a phone that runs complete operating system software providing a standardized interface and platform for application developers. For others, a smartphone is simply a phone with advanced features like e-mail, Internet and e-book reader capabilities, and/or a built-in full keyboard or external USB keyboard and VGA connector. In other words, it is a miniature computer that has phone capability.

Carputer is the predominant term used to describe a category of mobile computer, designed or modified to specifically be installed and run in automobiles. Historically these were based on industrial personal computer technology, but as smartphones and PDAs have become more powerful, and have included useful technologies like GPS and bluetooth they have become the predominant base platform for developing carputers.