Hello,

Where does the front end application programs reside in Linux OS. Will they run in user space?

Thanks
NSR Prasad

First, what is the context of your question? Are you considering trying Linux? Have you tried it?
What computing environments are you familiar with?

You install applications onto a Linux installation---much as you would in Windows, but with more methods to choose from. For most things, you don't see the "front end"--or the back end. An obvious exception is the printing system, where you have front-end drivers that interface with apps, and back-end drivers that talk to printers.

What do you mean by "user space"? Generally programs will run as part of some parent process--eg the the user's shell. Programs can also be commanded to run in background.

From a virtual-memory and privelege-separation point of view, all programs run in user-space. Only the kernel and kernel modules run in kernel-space. When programs need resources from the kernel, they make use of a system call (handled by libc and a kernel interface) to do so.

As opposed to my attempts, this guy seems to know what he is talking about....
I don't think or kernel or kernel modules as "programs". By themselves, they don't do anything useful. To many people, I think program is taken as the thing that performs a particular function.

....from the great semantic swamp...

Yes, I would not consider the kernel or modules programs, though they do behave similarly to one. My intent was to clearly define the line between user-space and kernel-space.

Based on the OP's reference to user-space, I assumed his question of where they reside was in the context of process (address) space, and not physical (i.e., disk). I could, however, be way off base here.

I think you are closer to the base---I'm more like deep left field....

Sorry for nit-picking but...

They do do something useful - running the computer and all its hardware components, its just not directly useful to the user, but they are still programs.

A better word for that would be 'application'. I'd say a program is any piece of software which runs, an application is something that does a specific function for the user, eg. a web browser or a spreadsheet or something like that.

Well, precision can be good and useful at times. No point in being unclear. We're all friends here, right?

"The kernel" is a device-control program: if you can pop off the case of your computer and "see something or touch it," then the kernel is what physically controls it. That includes: CPU, memory, the motherboard, peripheral devices, keyboard, mice, displays. The kernel provides the basic environment in which all programs are run. It creates and patrols the notion of "files." But ultimately, hardware control is all that it does.

"The system environment that you interact with every day" is actually composed of many programs, all running at the same time within the environment that the kernel has created. And, unlike Microsoft Windows, you have more control over these and can "see" them. Linux is a loosely-coupled system.

For example, let's say that you are looking at this page in FireFox and you decide to print it. How many programs are "helping" you? ...

• The graphical display that you're looking at is built by the XWindows (or XOrg) subsystem.
• The shell, or control-environment including taskbars and icons, might be Gnome, KDE, or something else ... running "under" XWindows/XOrg.
• The FireFox browser is an application, interacting with each of these.
• You sent an item to the printer, so the CUPS (or LPD) program is sending that output, a page at a time, to the printer.
• Oh yes, there's a clock ticking away at the bottom of the screen... yep, another program.

All of these programs are running, simultaneously, in the environment created for all of them by the kernel.