C | Data Types | Question 1
Predict the output of following program. Assume that the numbers are stored in 2’s complement form.
#include<stdio.h> int main() { unsigned int x = -1; int y = ~0; if (x == y) printf("same"); else printf("not same"); return 0; } |
(A) same
(B) not same
Answer: (A)
Explanation: -1 and ~0 essentially have same bit pattern, hence x and y must be same. In the comparison, y is promoted to unsigned and compared against x (See this for promotion rules). The result is “same”. However, when interpreted as signed and unsigned their numerical values will differ. x is MAXUNIT and y is -1. Since we have %u for y also, the output will be MAXUNIT and MAXUNIT.
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