Can anyone tell me what is the difference between borland Pascal 7.0
and Turbo Pascal 7.0 ?
Can I write Dos applications using Borland Pascal 7.0, and is the
source code compatible with Turbo Pascal 5.x ????

I guess Borland Pascal is DOS, DPMI and WINDOWS hosted and targeted,
while Turbo Pascal just does DOS.

Yes. Borland includes Turbo.

Well... Some of it. Most of it, in fact, but 5.0 did not know
about objects while 5.5 did, which makes a great difference.
Anyway, without objects, you can make 5.0-compatible code
in 7.0

Albert.