加减计算器

代码说明：

说明：  (1) 加减数和被加减数的输入位数为1-4位； (2) 相加结果显示要考虑进位的输出显示（即5位输出）； (3) 注意对“0”—“9”、“+”、“＝”以外按键输入的处理； (4) 注意对相加结果进行十进制处理； (5) 输入加数和被加数时，显示器上显示的数字要像平时用的计算器输入一样，即：每输入一个数字，原来显示的数字要往左移； (6) 可以完成累加功能。((1) The input digits of the additions and subtractions and the additions and subtractions are 1-4 digits; (2) The additive result shows that the carry output display (i.e. 5-bit output) should be considered. (3) Attention should be paid to the processing of keyboard input other than "0"-"9", "+" and "="; (4) Attention should be paid to decimal processing of the additive results. (5) When the additive and the additive are input, the number displayed on the display should be the same as that input by the usual calculator, that is, every number input, the original number displayed should move to the left; (6) Accumulative function can be completed.)