Question

#include<stdio.h>
int main(void)
{ 
  signed int a=-1;
  unsigned int b=1;
  int c= a+b;
  printf("%d\n",c);

  return 0;
  }

According to the rule of Implicit type conversion, if one operand is unsigned int,the other will be converted to unsigned int and the result will be unsigned int in a binary operation.
so here as b is unsigned int, a should be type casted to unsigned int.As unsigned int is always +ve , so the value of a will be 1.so c=1+1=2.But the output is 0.How ?

Answer 1

-1, when cast to unsigned will become the largest possible value for that type — e.g. with a 32-bit unsigned, it’ll be 4,294,967,295. When you add 1 to that, the value “wraps around” to 0.