Re: [Dev-C++] memory allocation

[Abhijit S. <mu...@gm...>]

Greets, Oroszi and everyone.

> Hello!
>
> I would like to ask a question, not really related to "modern"
programming.
>
> In Borland C++ 3.11 (DOS version) can I allocate memory dynamically. I
mean, do
> I need page flipping and stuff like that, or is memory linear?
> What if I run Borland C++ written programs under Windows? Shall my
programs get
> the memory. How much can I get (in DOS and Windows).
>
> I need help quickly (today) so I would be very happy if you could answer.
> Thank you.
>
> --
> Greetings,
>    Balázs

In DOS (real-mode), memory is banked. So you need two thingies to address
it: the segment and offset. To make a pointer, given segment and offset, use
MK_FP(seg, off) and to find the segment and offset of a pointer, use
FP_OFF() and FP_SEG().

The segment is like a bank (they overlap, however), and the offset is the
memory location within the segment. Search on Google for more info. Or see
the X2 FTP, it's got a treasure-trove of info about MS-DOS programming:
http://sunsite.lanet.lv/ftp/mirror/x2ftp/msdos/programming/

However, in most general applications, you won't need to bother with them.
You simply call new or malloc(), and they return an appropriate far pointer
(depending on the memory modely you're using - small, tiny models don't use
far pointers). Only if you're doing some hardware-level stuff, you'll need
to bother with segments and offsets. In small, tiny and medium models, I
think you get 64k memory (a 16-bit pointer), and in huge, large models you
get 1 meg (a 20-bit far pointer). The other differences in these models are
the size of the data segments and global heap (I think... long time no
real-mode).

Also, in protected-mode DOS (DPMI), memory is linear. Use djgpp:
http://www.delorie.com/djgpp
for this, its a GCC port for DPMI. It's also got an IDE similar to
Turbo-C++, called RHIDE. You may or may not be able to use it with Dev. If
you're successful, post to this mailing-list for the welfare of humanity and
stuff.

HTH, and sorry for the late reply.
___________________________________________________________

Abhijit Shylanath

mu...@gm...
http://mudeth.tripod.com/