Dear Experts
Why we always hear that unix operating system is Multi User and Multi task. What does these two means. I have looked at some books and documents but couldn't find aclear explenation. Can we say Windows operating system is also multi user and multi task??
Thanks for your help in advances.
Cheers
Reza

See the descriptions:
multi-user
multitasking

Multi task is ability to maintain schedule for more than one process. As normally number of processes exceeds by far number of CPUs in a system, the system scheduler becomes the core part of such multitasking. There is no real multitasking though, as only one process occupies processor's registers at time. However as it happens relatively fast it creates illusion of many processes flowing simultaneously. Multitasking systems is an opposition to mono tasking system as MS-DOS was. While in MS-DOS it was possible to have some processes to simulate simultaneous execution it was dome by using range of interruptions that is not a part of the system and worked more as a switch, while one process was working, until user would not designate manually recourses to the next process it would keep the current state.
Yes Windows XP is by all means a multitasking system.
Multi-User system implies that system can handle simultaneously more than one user. It means that system knows how to recognize the user, how to keep the environment and how to separate recourses between users.
Yes Windows XP is by all means a multi-user system.
The both Windows XP and UNIX may have many users connected using different hardware means and having sessions simultaneously.
I suspect you ask it as a point of comparison to Window/UNIX advantages/disadvantages. Let me tell you that the major advantage of any UNIX system is its simplicity. UNIX has very simple architecture compounded of many subsystems. If something is going wrong you always can trace problem to the specific subsystem. Each subsystem is mostly independed and may be stopped/started/ refreshed with no influence to anything else. Each subsystem is open, it means it may be discovered by regular mortals simply by reading man page; it has no "magic" involved. UNIX despite its evolution had some revolutionary steps in development and does not have to take increasing care of backward compatibility in its worst sense, because most of the programs can be recompiled with little efforts.
As system is modular it is easily upgradeable, many different teams of developers can coexist with little disturbance to one another, they don’t have create “the system”, they are responsible for a little part and this way makes the system in general very reliable. There are many competing projects; each try to prove its module is the best.
Sorry for tedious port.

Thanks a lot for your patience in teaching me.
Sometimes I am hearing that some software companies are claiming that the trend is towards Windows not unix what is your opinion. I am asking this question because I love unix and I can't understand this rumors.

If ask you ask I, here’s my prognosis:
As we have 3 branches of "real" UNIX
1. Linux, will progress as a humble server platform with virtually no decent desktop applications it has little chance to become a mainstream. There’s almost nothing to offer for a modern computing: no real advanced photo editing, no advanced movie-video editing, no reliable office program (try forge your resume once in OpenOffice to assent to this my statement ;-) ). Linux will have profound influence on the entire UNIX community though, as all new, advanced tools come from there… As to my taste BSD still much better choice by many reasons… I think Linux will transform itself to something else or it will dye out to the OS X systems.
2. OS X had become the best UNIX ever, and the best OS in a existence. No one who has spent at least two hours in from of Tiger can go back to anything else. It unites best ever UNIX, that is BSD UNIX with stunning Aqua GUI. It Has all the commercial applications of importance running on it: MS Office (much refined than PC version), Adobe products, extensive multimedia tools, Video editing tools and so on. Great platform.
3. Big UNIXes such as Solaris and AIX (and almost dead HP) have seen better times. Solaris offers a lot but I kind of stumbled by their prices including the cost of service. All three had been the mainstream with corporative environment but gradually lose ground to Linux and OS X. Some 5-6 years ago Sun (along with ver much dead Silicon Graphics) had been a major player on graphical systems market. As far as I know this market was lost by Sun completely. AIX is one hardware platform system but for industrial environment, to my taste it is the best. It is very reliable with outstanding technical support and great, easy to use administration tools. It is possible to manage complete powerful system with sophisticated volume management after mere one week training.

Windows. I think Microsoft is in demise. It has been postponed for four years in row the release of the new version and it speaks for itself. If money hungry MS postpones release it means it implies that HUGE number of problems that it may cause massive departure from this platform. The whole conception behind Windows with deep interlinking of all embedded components made the project unmanageable. It is not only that it takes too long to publish release, it will take as much long to produce any relevant updates. I don’t think Microsoft as a producer of operating systems will make it to 2010.

Tnanks a lot for your so much informative explenations.
Regards
Reza

Thanks a lot for introducing the links to me.