C | Pointer Basics | Question 1

What is the output of following program?

# include <stdio.h> 
void fun(int x) 
{ 
    x = 30; 
} 
  
int main() 
{ 
  int y = 20; 
  fun(y); 
  printf("%d", y); 
  return 0; 
} 

(A) 30
(B) 20
(C) Compiler Error
(D) Runtime Error

Answer: (B)

Explanation: Parameters are always passed by value in C. Therefore, in the above code, value of y is not modified using the function fun(). So how do we modify the value of a local variable of a function inside another function. Pointer is the solution to such problems. Using pointers, we can modify a local variable of a function inside another function. See the next question.
Note that everything is passed by value in C. We only get the effect of pass by reference using pointers.

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