Function 3Eh (62)        Close a File Handle

    Flush the file's buffers, close the file, and release the file handle.

       On Entry:      AH         3Eh
                      BX         File handle

       Returns:       AX         Error code, if CF is set

       Error codes:   6          Invalid handle

                      Call Function 59h for extended error code information.

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    This function flushes the file's buffers, closes the file, releases
    the handle, and updates the directory.