DosMemAvail()                 Get total available extended memory.
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 Function : Get total available extended memory.

 Syntax   : USHORT BLXAPI DosMemAvail(PULONG bytesavail);

 bytesavail Pointer to a long integer to receive the number of bytes of
            available extended memory.

 Return   : The total available extended memory in bytes.

 DosMemAvail() returns the amount of extended memory available which may be
 allocated with DosAllocSeg() and DosAllocHuge().

 Example:

    #include <stdio.h>
    #include <blx286.h>
    void main (void)
    {
    ULONG       ext_mem_avail;
    if (DosMemAvail(&ext_mem_avail) != 0)
       {
       printf("Unable to determine free extended memory\n");
       exit(255);
       }
    printf("Free extended memory is %08X bytes\n",ext_mem_avail);
    }