有符号数与无符号数的上溢与下溢问题

有符号数与无符号数的上溢与下溢问题 以8位为例：

#include<stdio.h>
int main()
{
	//8位有符号的最大数
	char a = 127;
	printf("a = %d\n",a);
	a++;
	printf("a = %d\n",a);
	printf("************\n");
	//8位有符号的最小数
	char b = -128;
	printf("b = %d\n",b);
	b--;
	printf("b = %d\n",b);
	printf("************\n");

	//8位无符号数的最大数
	unsigned char c = 255;
	printf("c = %u\n",c);
	c++;
	printf("c = %u\n",c);
	printf("************\n");
	//8位无符号数的最小数
	unsigned char d = 0;
	printf("d = %u\n",d);
	d--;
	printf("d = %u\n",d);
	printf("************\n");
	unsigned char i = 255;
	i+=3;
	//应该打印 出2
	printf("i = %d\n",i);
	printf("************\n");
	char j = 127;
	j+=3;
	//应该打印出-126
	printf("j = %d\n",j);
	return 0;
}

仔细来看，溢出会造成一个范围内的循环。输出结果如下：

a = 127
a = -128
************
b = -128
b = 127
************
c = 255
c = 0
************
d = 0
d = 255
************
i = 2
************
j = -126