Clients

The front-end or the client is commonly the application which interacts with the end-user by the keyboard, display and pointing device like mouse. The client portion has no data access responsibilities. It concentrates on requesting, presenting the data managed and processing through the server portion. A client workstation can be optimized for its job. For instance, it might not require huge disk capacity or it might advantage from graphic capabilities. Client deals with data presentation and user interface.

The client hardware is the desktop machine which runs client software. It could be a workstation or a micro. The client hardware has to be robust sufficient to support the presentation needs and the client based processing of the application.

The client software formulates data requests and passes the requests to the network software. Network software sends the requests to the server and accepts the results from the server and passes the results reverse to the client software. Then the client software should perform some application logic on the results of the request before passing it on to the presentation parts of the software.

The presentation component produces the interface in which the user interacts and views with. It is frequently, but not always, a graphical user interface. The GUIs gives a graphic-oriented presentation front-end to applications and gives (or simulate) multitasking processing (the ability  to  run  two  or  more  applications  at  the  similar  time).  The major windowing environments are Presentation Manager from IBM, Windows from Microsoft, OpenLook from USL and Motif from Open System Foundation (OSF).

For those who have not seen or used a windowed environment: By using a mouse as a pointing device, users select options through positioning the cursor on the item of choice and clicking while pressing a button on the mouse. Options are displayed as lists or icons. If a user must select from a valid list of values a scrollable list box appears and the user scrolls by the list until the choice is highlighted and then clicks. The user can switch among multiple tasks and/ or programs. Every task or program is in its own window and the user can position the windows so which they are side-by-side or overlayed. Each effort is establish to decrease keyboard use. The interface hides most and if not all, of the needs for data retrieval and system administration from the user.

There is also an operating system running on the client hardware that may or may not be the similar as the server’s operating system. The client operating system must be robust sufficient to support the presentation processing and application logic processing needs for the applications. Every of the main windowing environments were designed for a particular operating system. Presentation Manager under OS/2Windows runs under DOS, and Motif and OpenLook under UNIX.

There is also communications software that is running on the client hardware. The client-based network software will handles the transmissions of requests and receives the results of the requests. Therefore, individual network operating systems do not support all available server and client operating systems.

The client should also be executing runtime support for applications produce with client or server development tools. Using the development tool and the application logic is specified and partially executable code is generates. The generated code is executed through the client’s runtime version of the software.In some cases, a client is really a server acting as a client (then the server is known as an agent) through requesting data from another server.