small c program

[Bill Cunningham]

Can a small C program it put at int 19 and look at 0x7c00? This may or
may not be considered a C question I guess. Or is C too small to reside in
MBR?

Bill

 

[Richard Heathfield]

Bill Cunningham said:

Can a small C program it put at int 19 and look at 0x7c00?

This seems to be a question about a particular platform. I suggest you ask
your question in a newsgroup that deals specifically with programming for
that platform.

 

[Malcolm]

Can a small C program it put at int 19 and look at 0x7c00? This may or
may not be considered a C question I guess. Or is C too small to reside in
MBR?

Most C compilers will allow you to set a pointer to an absolute address.
However this is of course completely non-portable, and it might not produce
the results you expect, depending on the system.

 

[Richard Heathfield]

Malcolm said:

Most C compilers will allow you to set a pointer to an absolute address.
However this is of course completely non-portable, and it might not
produce the results you expect, depending on the system.

Yes, you'll generally be disappointed by the results if you're using a
protected-mode OS. Note, also, that to do this you will require a cast.
(That in itself is often a sign that you're doing something a bit worrisome
- but if you have to hack the hardware under a real-mode OS, it's certainly
a handy port in a storm.)

 

[Brytison]

C-compiler is dependce the OS, C program can't look 0x7c00 under the
protected-mode OS. use real-mode you will get it.

 

[Mark McIntyre]

Malcolm said:


Yes, you'll generally be disappointed by the results if you're using a
protected-mode OS.

Depends. Some people find dialog boxes advising you about illegal
memory access etc quite exciting....