UNIT 1CLIENT SERVER OPERATING

SYSTEM

CLIENT SERVER COMPUTING

CLIENT ANATOMY

All Client applications request the services of a server.

What makes client applications different is what triggers the request and what GUI is used. Based on these differences, we can classify clients into three categories: Non-GUI Clients, GUI Clients, OOUI Clients.

1. NON-GUI CLIENTS

Non-GUI client applications generate server requests with a minimal amount of human interaction. Non-GUI clients fall into 2 sub-categories: Non-GUI clients that do not need multitasking:

Examples include automatic teller machines, barcode readers, cellular phones, fax machines.

Non-GUI clients that need multitasking: Examples include robots, testers and daemon programs. These clients often require very granular, real-time, event-driven multitasking services.

2. GUI Clients

Simple GUI dialogs use the object/action model where users can select objects and then select the actions to be performed on the chosen objects.

Used in Windows 3.X and OSF Motif applications, as well as most of today’s form-based Web pages.

3. Object-Oriented User Interface Clients

It provides a highly iconic, object-oriented user interface that lets you directly manipulate objects on a screen.

OOUI are used by information workers doing multiple, variable tasks whose sequence cannot be predicted.

Examples include Executive and Decision-Support applications, multimedia-based training systems, sytem management consoles and stockbroker workstations.

GUI OOUI

A graphic application consists of an icon, a primary window with a menu bar, and one or more secondary windows.

Icons represent a running application.

Users start applications before selecting an object to work with.

Choose object; then choose action from menu bar.

A graphic applications consists of a collection of cooperating user objects. Everything that you see is an object. Each object is represented by an icon.

Icons represent objects that may be directly manipulated.

Users open the object on the desktop, which causes a window view of the object to be displayed.

In addition to choosing actions from menu, a user can drag objects to icons to perform operations; for example, dragging a file to a printer icon.

GUI Vs OOUI

CLIENT NEED FROM AN OS

All Client applications need some mechanism to communicate service requests and files to a server.

GUI and OOUI clients work best with a thread-like mechanism for handling the background requests.

By using seperate threads for the user interface and background processing, the program can respond to user input while a seperate thread handles the interaction with the server.

Priority-based, preemptive multitasking is also required to respond to multimedia devices and to create client applications where multiple dialogs are displayed in parallel.

The most important requirement of a client OS is to host mobile code in a secure fashion. This lets servers ship mobile code to clients on an as-needed basis.

CLIENT OS TRENDS

The desktop is becoming more fragmented.The universal client is really a Web Browser.There will be a huge demand for super-fat PCs.There will be a huge demand for ultra-thin PCs.Embedded clients will be everywhere.

SERVER OS TRENDS

According to IDC, the fastest growing category is application servers.

All server Oss – including NetWare, OS/2, NT, and all the Unixes – are going after this high-growth market.

SERVER OS TRENDS

In 1997, NT, UNIX/LINUX, NetWare, OS/2

SERVER OS TRENDS

But, Revenue in 1997, UNIX, NetWare, NT, OS/2