Overview

This unit gives  the  pascal  programmer  access  to  an XMS heap for
Pascal.  It uses a similar system to the Pascal standard heap.

This unit is ideal  for  programmers  requiring  many large blocks of
data.

Requirements

Turbo Pascal 6
TPXMS.TPU       (Public Domain by Vernon E. Davis, Jr.)
DosMem          (Public Domain by Pure Power Software, PSDSM)

Both PSDSM and TPXMS should  be  available  where  you  obtained this
file.

Limitations

When running in real  mode  you  cannot  simply  use  the  XMS memory
provided by HIMEM.SYS with  pointers.   Thus you can't simply plug in
this unit and assume that your programs will now use XMS.

You can only access  data  in  conventional  memory.   Thus  if  your
program uses 400 kb and the  PC  only  had  500 kb free, your program
is still limited to a  largest  block  size  of 100 kb, but with this
unit you can swap data in and out of the XMS memory.

How it works

HIMEM requires a request  for  memory.   Usually  HIMEM  only permits
32 blocks, that is, only  32  handles  are  issued.   Thus requesting
a new handle each  time  is  silly  as  one  often  uses more than 32
pointers in a program, often more than the 128 HIMEM maximum.

So, when you allocate your XMS  heap  with GetXMSHeap, the unit takes
a block (one handle)  from  HIMEM.   You  can then access this memory
in any size chunks  you  wish,  from  blocks  of  1 byte to blocks of
640 kb.  The unit has its own  handles  and can allocate many handles
to the XMS heap (set by BMaxPointersB).

Your programs will  now  use  handles  to  the  XMS  heap (not to XMS
controlled by HIMEM), not only  pointers.   Handles  point to the XMS
heap, p