This document discusses different types of client-server computing. It describes three categories of clients: non-GUI clients like ATMs that require minimal human interaction; GUI clients that use graphical user interfaces; and OOUI clients that allow direct manipulation of objects. It also outlines the needs of clients from an operating system, including communication with servers, multitasking capabilities, and secure execution of mobile code. Trends are discussed as well, such as the growing diversity of client devices and the rise of application servers.

1. CLIENT SERVER
COMPUTING
UNIT 1
CLIENT SERVER OPERATING
SYSTEM

2. 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.

4. 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.

6. 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.

8. 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.

10. GUI Vs OOUI
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.

11. 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.

12. 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.

13. 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.

14. SERVER OS TRENDS
In 1997,
 NT,
 UNIX/LINUX,
 NetWare,
 OS/2

15. SERVER OS TRENDS
But, Revenue in 1997,
 UNIX,
 NetWare,
 NT,
 OS/2