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Programming and Data Structures · Programming in C
Official IIT answer key · IIT Kanpur · Audited Aug 2026
GATE CSE 2015 Set 1 Q11 · NAT · 1 mark
void f1(int a, int b) {
int c;
c=a; a=b; b=c;
}
void f2(int *a, int *b) {
int c;
c=*a; *a=*b; *b=c;
}
int main(){
int a=4, b=5, c=6;
f1(a,b);
f2(&b, &c);
printf("%d",c-a-b);
}Key concept
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Topic notes
In GATE CS, Programming in C is tested extensively through rigorous code tracing, pointer mechanics, and fundamental semantics rather than high-level syntax trivia. Questions emphasize pointer arithmetic and multidimensional array decay, storage classes (especially static local variables), evaluation order, side effects of increment/decrement operators, parameter passing mechanisms (pass-by-value vs pass-by-reference), and recursive program state tracking. The topic features a nearly balanced split between NAT and MCQ items across 1-mark and 2-mark categories, demanding precise, bug-free execution traces without a compiler.
Full Programming in C guide →The output of the following C program is … void f1(int a, int b) int c; c=a; a=b; b=c; void f2(int *a, int *b) int c; c=*a; *a=*b; *b=c; int main() int a=4, b=5, c=6; f1(a,b); f2(&b, &c); printf("%d",c-a-b);
Topic-wise GATE CS PYQs with verified steps
Independent practice explanation verified by the GateAI team. GATE is conducted by the IITs; question text follows the official paper.