该子程序必须是透明的主程序。这意味着用于子程序任何寄存器（包括CC登记和用于通过目前的N和DIFF值的子程序的登记）必须推到堆栈的子程序的开始和拉在最后的子程序堆栈。-The subroutine MUST BE transparent to the main program. This means that any registers used in the subroutine (including the CC register and the register used for passing the current N and DIFF values to the subroutine) must be pushed onto the stack at the beginning of the subroutine and pulled off the stack at the end of the subroutine.