What is difference between distributed and time sharing computer?

Time sharing means that many users share a single computer. This

was in the days of big mainframes and dumb terminals. It is an

example of multitasking (many processes running on one processor).

Time slice is one way that processors can multitask. This was the

origin of client/server programming, many clients share the

server.

Distributed computing is when a process running on one computer

uses software modules running on many other computers. The

Seti-At-Home screensaver is an example of distributed computing.

The screensaver running on your computer calculates a small set of

all the data collected by Seti when you processor is idle. The main

computer collects all the analysed data from thousands of running

screensavers.

The following is about preemptive/non-preemptive multitasking.

It is concerned with only one computer. In a time slicing computer,

there is an algorithm that decides how much time on the processor

each of the processors need. It can very this dynamically. If a

certain process doesn't voluntarily give up it's control of the

processor, the central time-slicing process can force it off the

processor. Most operating systems use time-slicing. Unix, Linux, OS

X, Windows XP, etc. all use it.

In a distributed/cooperative computer, each process has to

willingly give up its control of the processor when it's done. If a

process doesn't give up control, then the whole computer crashes.

This is a lot less stable. Any Mac OS prior to OS X uses

distributed processing.