On compilation on the program, an error will be displayed.

Question

Read the following program 

# include<iostream.h>

int main()

{

cout<<sum(2, 3);

}

int sum(int x, int y)

{return (x + y);}

On compilation on the program, an error will be displayed. Identify and explain the reason. How can you rectify the problem

Answer 1

The compilation of the program starts from the first line and next line and so on( i.e. line by line). While compiling the line cout<<sum(2, 3); The compiler does not understand the word sum(2, 3) because it is not declared yet hence the error prototype required. To rectify this problem there are two methods

First method

Give the function definition just before the main function as follows. 

# include<iostream>

using namespace std;

int sum(int x, int y)

{return (x+y);}

int main()

{

cout<<sum(2, 3);

}

Second Method 

Give the function declaration(prototype only) in the main function as follows.

# include <iostream>

using namespace std;

int main()

{

int sum(int, int);

cout<<sum(2, 3);

}

int sum(int x, int y)

{return (x+y);}