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diff --git a/v4.0/src/MAPPER/CLOSE.ASM b/v4.0/src/MAPPER/CLOSE.ASM
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+;0
+page 80,132
+
+title CP/DOS  DosClose  mapper   * * *
+
+dosxxx  segment byte public 'dos'
+        assume  cs:dosxxx,ds:nothing,es:nothing,ss:nothing
+;
+; ************************************************************************* *
+; *
+; *      MODULE: DosClose
+; *
+; *      FUNCTION: This module will close a file or a device.
+; *
+; *      CALLING SEQUENCE:
+; *
+; *                PUSH  WORD  FileHandle ;  File Handle or device handle
+; *                CALL  DosClose
+; *
+; *      RETURN SEQUENCE:
+; *
+; *                IF ERROR (AX not = 0)
+; *
+; *                   AX = Error Code:
+; *
+; *                   o   Invalid file handle
+; *
+; *
+; *      MODULES CALLED:  DOS int 21H function 3EH
+; *
+; *
+; *************************************************************************
+
+        public  DosClose
+        .sall
+        .xlist
+        include macros.inc
+        .list
+
+str     struc
+old_bp     dw     ?
+return     dd     ?
+FileHandle dw     ?          ; file or device handle
+str     ends
+
+
+DosClose  proc   far
+        Enter   DosClose               ; push registers
+
+; Only files are closed.  Devices are not closed, since OPEN creates
+; a dummy device handle without actually openning the device.
+
+        mov     bx,[bp].FileHandle     ; load the handle
+        mov     ax,bx                  ; check for device handle
+        neg     ax                     ; if device handle, return
+        jns     GoodExit               ; do not close the device
+
+FileCloseRequest:
+        mov     ax,03e00h              ; load opcode
+        int     21h                    ; close the file
+        jc      ErrorExit              ; return if error
+
+GoodExit:
+        sub     ax,ax                  ; else, set good return code
+
+ErrorExit:
+        mexit                          ; pop registers
+        ret     size str - 6           ; return
+
+DosClose  endp
+
+dosxxx  ends
+
+        end