1.1  What is a Distributed System ?

                Definition: A Distributed System is a collection of independent computers that appears to the users of the system as a single computer.

                 This definition has two aspects. The first one deals with hardware: the machines are autonomous. The second one deals with software: the users think of the system as a single computer.

        Examples: 1. Network of workstations in university or company department. In addition to each user's personal workstation, there might be a pool of processors in the machine room that are not assigned to specific users but are allocated dynamically as needed. The whole system looked and acted like a classical single-processor-timesharing system.

                           2. A factory full of robots, each containing a powerful computer for handling vision, planning, communication, and other tasks.

                          3. A large bank with hundreds of branch offices all over the world. Each office has a master computer to store local accounts and handle local transactions. In addition, each computer has the ability to talk to all other branch computers and with a central computer at headquarters.