Evaluate the output of this C program that uses logical negation: #include<stdio.h> int main() { int x = 10, y = 20; if (!(!x) && x) printf("x = %d ", x); else printf("y = %d ", y); return 0; }
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Ay = 20
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Bx = 0
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Cx = 10
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Dx = 1
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ENo output
Answer
Correct Answer: x = 10
Explanation
Introduction / Context:This item checks how logical negation interacts with nonzero integers in C. Any nonzero value is considered true. Applying ! flips truthiness, not the numeric magnitude (except reducing truthy to 0 and false to 1).
Given Data / Assumptions:
x = 10(nonzero → true),y = 20.- Expression:
!(!x) && x. - Short-circuit semantics of
&&apply.
Concept / Approach:!x converts any nonzero to 0 and zero to 1. Thus !x becomes 0, and !(!x) becomes 1. The second operand of && is x (which is nonzero). Therefore, 1 && 10 is true, so the if branch executes, printing the current numeric value of x (10).
Step-by-Step Solution:
!x → 0 because x is nonzero.!(!x) → 1.1 && x → true because x is nonzero.Print: x = 10.Verification / Alternative check:Replace x by 0 and re-run to see the else branch. Replace x by −5 and note that it is still treated as true.
Why Other Options Are Wrong:
y = 20: would print only if the condition were false.x = 0 / x = 1: the program prints the actual stored value (10), not a truthy/falsey normalized value.No output: one branch must print.Common Pitfalls:Confusing logical truthiness with numeric value; assuming !10 creates −10 (it does not).
Final Answer:x = 10.