C++ Function Calling

Introduction

To call a function in our program, we specify the function name followed by empty parentheses as the function has no parameters: 

#include <iostream> 

void myfunction(); // function declaration 

int main() // w w w  .ja v  a2s .  c  o  m
{ 
    myfunction(); // a call to a function 
} 

// function definition 
void myfunction() { 
    std::cout << "Hello World from a function."; 
}

To call a function that accepts one parameter, we can use: 

#include <iostream> 

int mysquarednumber(int x); // function declaration 

int main() //w  w  w. ja  v  a 2  s .  c  o  m
{ 
    int myresult = mysquarednumber(2); // a call to the function 
    std::cout << "Number 2 squared is: " << myresult; 
} 

// function definition 
int mysquarednumber(int x) { 
    return x * x; 
}

We called a function mysquarednumber by its name and supplied a value of 2 in place of function parameter and assigned the result of a function to our myresult variable.

What we pass into a function is often referred to as a function argument.

To call a function that accepts two or more arguments, we use the function name followed by an opening parenthesis, followed by a list of arguments separated by commas and finally closing parentheses.

Example: 

#include <iostream> 

int mysum(int x, int y); 
int main() //from   w  ww . j  a  v a  2  s. com
{ 
    int myresult = mysum(5, 10); 
    std::cout << "The sum of 5 and 10 is: " << myresult; 
} 

int mysum(int x, int y) { 
    return x + y; 
}



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