GATE CS 2015 Set 1 — Question 34
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Programming & Data Structures → C Programming → Functions & Recursion
Last updated
Question
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);
}
Correct answer
-5 to -5
Solution
1.Initial values in
main: a = 4, b = 5, c = 6.2.Call
f1(a, b): This function takes arguments by value. It swaps the local copies of a and b inside f1, but does not affect the variables in main. After f1, values in main remain: a = 4, b = 5, c = 6.3.Call
f2(&b, &c): This function takes pointers (addresses). It swaps the values pointed to by a (which is &b of main) and b (which is &c of main).*arefers tobin main.*brefers tocin main.- The swap logic:
temp = b; b = c; c = temp; - After
f2,bbecomes 6 andcbecomes 5. - Values in
mainare now:a = 4,b = 6,c = 5.
printf("%d", c - a - b):- Calculation: .
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