Question about registers

[na_th_an]

It shows "CMD.EXE" as QB is run thru' the MSDOS VM.

[LooseCaboose]

And what exactly are processes? *Presses CTRL+ALT+DEL on a Win/XP machine* IEXPLORE.EXE is a process?

A process is an execution context, something that is running. In Windows you have executables, such as iexplore.exe, that file contains a section of code (instructions) and a section of data (variables) among other things. When the operating system runs that program the code and data are loaded into memory (not necessarily all of it because of memory management) and one of the contexts I mentioned earlier is assigned to it. The program counter register is then used to point to the currently executing instruction and the program can be run.

Not all processes are based on executable files, the OS kernel often creates a number of virtual processes, by loading some of the kernel code into memory and assigning a context to it, for managing things like memory, the file system, networking and the idle process (which gets run when there isn't anything else to run).

Actually, Zack, Windows or Linux are just re-using multitasking concepts that were developed on operating systems back in the early 1960's.

When computer scientists talk about "modern operating systems" they mean protected multiprocessing operating systems, which date back to the late 1960's, early 1970's. Multitasking has improved in operating systems quite drastically however. Linux isn't actually process based like older systems, but schedules threads which are a form of light weight process and require less context overhead. Other improvements include preemptive multitasking, preemptive kernels, shared process address spaces (copy on write) and process priorities (some operating systems can even mix hard and soft realtime processes). But as you say, the basic principles haven't changed much in the past 30 years, if it ain't broke don't fix it.

[Zack]

If those are processes, then what are the "Applications" listed that are running...Well, yes, they're applications, but you just said every application is a process.

[stevie]

every square is a rhombus, not every rhombus is a square.


applications are generally programs that involved interactive use to accomplish personal tasks -- it can include stuff like word processors, spreadsheet programs, and even a program to schedule when your meant to put in a fresh suppository.

However, many processes you are seeing are things that you don't even know are going on -- performing important background tasks, etc.

so, like I said, every application is a process, but not every process is an application.

[adosorken]

...and even a program to schedule when your meant to put in a fresh suppository.

I am not even gonna go there

[Rhiannon]

...and even a program to schedule when your meant to put in a fresh suppository.

I am not even gonna go there

That's about as bad as eQuuskia's bovine artificial insemination scheduling programs. :lol:

[LooseCaboose]

If those are processes, then what are the "Applications" listed that are running...Well, yes, they're applications, but you just said every application is a process.

An application is a more user friendly way of viewing a process or group of processes. An application can be made up of several processes or more often several threads. For example something like Internet Explorer could have one thread/process for fetching information from the network connection and another for rendering the information on the clients screen. The two process/threads are then scheduled independantly giving the application as a whole more cpu time than one that is comprised of only a single process. Dynamic Link Libraries (dll's) can contain code that can either be used as separate functions or loaded up as a separate process/thread. Having applications with multiple processes driving them is also a really good idea on multiprocessor and hyperthreading machines.

Some of the other processes you see listed are background tasks (or daemons, if your in the *nix world) which perform services. For example you will see processes like csrss.exe, svchost.exe and explorer.exe in the process list when you have nothing but a blank desktop and no applications listed. Svchost does a number of things including allowing processes to use dynamic link libraries and csrss is responsible for running the graphics subsystem. Explorer.exe is an interesting process, it is run when you open a folder, but it is also visible in the process list when you aren't viewing anything. This is because explorer.exe is also used to display the desktop and start bar, if you kill it your desktop will vanish and restart when Windows automatically restarts the killed process.

[adosorken]

In Windows 9x, if explorer.exe would die, Windows would automatically respawn it. However, if you used any other shell, it would not respawn anything. What's up with that? I always wondered about that

[LooseCaboose]

In Windows 9x, if explorer.exe would die, Windows would automatically respawn it. However, if you used any other shell, it would not respawn anything. What's up with that?

AFAIK its because explorer (and internet explorer which shares some of the same code I think) are actually part of the operating system, the kernel (or one of the services) will detect when explorer.exe isn't running and restart it, but probably wont check for other shells.

Bolting stuff into the kernel is (IMHO) Microsoft's biggest problem in developing operating systems, to attain faster response from things such as the gui and explorer the tie them into the kernel, this is a bad idea because bugs in explorer can crash the OS and it makes the OS far more bulky. Explorer also uses a number of tricks to make it render faster by writing directly to the kernels graphics buffers instead of using the api calls.

You could try renaming your shell explorer.exe. Sorry if I missing the message between the lines, I can quite tell if your post is satire or not ;-)

[adosorken]

No I wasn't being satirical, I've written graphical shells for Windows 9x before and intentionally crashed them on purpose to see if they'd respawn, and they didn't. That's why I was asking.

Makes me wonder if I name my shell "explorer.exe"...if it will respawn or not. I shall check asap