It means that the computer (that it is running on) is running the program in an emulator, an operating system that is not the actual
operating system for the computer but is running under the operating system for the computer. That is, the native operating system
of the computer is running a program (emulator) that makes the native operating system appear to be another operating system.
For example, a pc can run Windows or Linux. Both are operating systems. Now suppose that someone wanted to try out Linux before
going to all the trouble of setting it up on his computer. If he had a Linux emulator, he could run that emulator under Windows
just like any other program, but the emulator would make it appear that he was actually running Linux to the user. If the user ran
a Linux program under that emulator, he would be running it in Linux emulation mode. The Linux emulator would serve as a go-between
between Window and the Linux program.
Apple computers now have capability of running Windows programs. I suspect (I don't know for sure) that they are using a Windows
Emulator. You could run M$ Word in the Windows Emulator on the Apple. The emulator would take "system calls" in the Word program
and translate the Windows calls to Apple operating system calls.
So, generally speaking, because of the emulator overhead the program running in emulation mode will probably run slower than it
would on the actual operating system. Also, since it is a real problem to write an emulator for a large operating system, I would
guess that there might be some problems. For example, if a Windows program occasionally crashes when running in Windows, imagine
what might happen if it is running in Windows emulation mode on another operating system!
A "system call" is an operating-system unique piece of a program. For example, you could write a program in a language like
FORTRAN. That program could be used in many different places. Before it is used it has to be "compiled" into code that runs on the
operating system of the computer, Unix, Linux, Windows, Apple O.S., etc. Different operating systems would require different final
code. Now, suppose that you added stuff to your FORTRAN program that made use of windows under Windows XP. Then, when that program
was compiled, it would have to run on a Windows computer or run in Windows emulation mode on another computer. If you tried to
compile it to run on a different operating system, the compiler would burp and give you an "unrecognized code" error. (So you need
an emulator as a go-between.)
I hope that is kind of clear. :)
Dean Kukral
----- Original Message -----
From: "chipo chika" <[log in to unmask]>
Sent: Monday, June 30, 2008 5:24 AM
Subject: [PCBUILD] Emulation mode
What does it mean for a program to run in emulation mode?
--
chipo chika
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