why minimum possible integer minus one becomes maximum possible integer in c-CodePudding

I know that c works in two's complement but still i can't undrstand how the program below gives me 2147483647 as output.

#include<stdio.h>
int main(){

int a=-2147483648;
a-=1;
printf("%d",a);

}

CodePudding user response：

Becuase an int can't contains the value -2147483648 - 1, so it result in an integer overflow, which leads to undefined behaviour. Undefined behaviour can result in anything.

CodePudding user response：

minimum number in twos comlement is 100000...0 if you reduce one from that it means computer will add -1 to it -1 in twos complement is: 11111...1 so if you add them the answer is 0111111...1 which is maximum integer or 2147483647