The client is a process (program) that sends a message to a server
process (program), requesting that the server perform a task (service).
Client programs usually manage the user-interface portion of the
application, validate data entered by the user, dispatch requests to
server programs, and sometimes execute business logic. The client-based
process is the front- end of the application that the user sees and
interacts with. The client process contains solution-specific logic and
provides the interface between the user and the rest of the application
system. The client process also manages the local resources that the
user interacts with such as the monitor, keyboard, workstation CPU and
peripherals. One of the key elements of a client workstation is the
graphical user interface (GUI).   Normally a part of operating system
i.e. the window manager detects user actions, manages the windows on the
display and displays the data in the windows.