C: numeric overflow problem

When more than one type of data can be stored in the maximum range values ​​will overflow.

Signed overflow bit highest distinction: the sign bit overflow will cause the number of positive and negative changes, but the most significant bit of overflow can lead to the most significant bit lost.

#include <stdio.h>

int main()
{
    char ch;

    //符号位溢出会导致数的正负发生改变
    ch = 0x7f + 2; //127+2
    printf("%d\n", ch);
    //  0111 1111
    //+2后 1000 0001，这是负数补码，其原码为 1111 1111，结果为-127

    //最高位的溢出会导致最高位丢失
    unsigned char ch2;
    ch2 = 0xff+1; //255+1
    printf("%u\n", ch2);
    //    1111 1111
    //+1后 10000 0000， char只有8位最高位的溢出，结果为0000 0000，十进制为0

    ch2 = 0xff + 2; //255+1
    printf("%u\n", ch2);
    //    1111 1111
    //+1后 10000 0001， char只有8位最高位的溢出，结果为0000 0001，十进制为1

    return 0;
}