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;* GetMem - Gets total size of memory and determines the largest amount of
;* unallocated memory available. GetMem invokes DOS Function 48h (Allocate
;* Memory) to request an impossibly large memory block. DOS denies the re-
;* quest, but returns instead the size of the largest block available. This
;* is the amount that GetMem returns to the calling program. See the WinOpen
;* procedure for an example of calling Function 48h to allocate unused memory.
;*
;* Shows:   BIOS Interrupt - 12h (Get Conventional Memory Size)
;*          Instructions - push     pop      ret
;*
;* Params:  None
;*
;* Return:  Long integer, high word = total memory in kilobytes (KB)
;*                        low word  = largest block of available memory (KB)
 
GetMem  PROC
 
        int     12h                     ; Get total memory in K
        push    ax                      ; Save size of memory
        mov     ah, 48h                 ; Request memory allocation
        mov     bx, 0FFFFh              ; Ensure request is denied for
                                        ;   impossibly large block
        int     21h                     ; Get largest available block in BX
        mov     ax, bx                  ; Copy to AX
        mov     cl, 6                   ; Convert paragraphs to kilobytes by
        shr     ax, cl                  ;   dividing by 64
        pop     dx                      ; Recover total in DX
        ret                             ; Return long integer DX:AX
 
GetMem  ENDP
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