DosVMAvail()                  Get amount of available virtual memory
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 Function : Get the amount of available virtual memory

 Syntax   : USHORT DosVMAvail(PULONG bytes);

 bytes      Pointer to a long integer to receive number of bytes of available
            virtual memory.

 Return   : The total available virtual memory in bytes.

 DosVMAvail() returns the approximate number of bytes of virtual memory
 available to the protected mode program.

 Example:

    #include <stdio.h>
    #include <blx286.h>
    void main(void)
    {
    ULONG       vmfree, xmfree, rmfree;
    if (DosVMAvail(&vmfree) == 0)
       printf("There are %08X bytes free virtual memory\n",
          vmfree);
    if (DosMemAvail(&xmfree) == 0)
       printf("There are %08X bytes free extended memory\n",
          xmfree);
    if (DosRealAvail(&rmfree) == 0)
       printf("There are %08X bytes free real memory\n",
          rmfree);
    }