Functions: simple examples


1a. “Hello world” program: sequential

#include <iostream>
using namespace std;

int main()

{
             cout<<"Hello world"<<endl;
             return 0;
}


1b. “Hello world” program: using a function ( void function with no arguments passed to it)

#include <iostream>
using namespace std;
                                 // function prototype.
void PrintHello();    // void function does not return any values, empty parameter list –
                                 // it does not receive any values

int main()
{
             PrintHello();   //function call – we are not passing any values to the function
             return 0;
}

void PrintHello()     //function header
{
            cout <<"Hello world!" <<endl;        //function body
            return;
}



2a. Print your number: sequential.

#include <iostream>
using namespace std;

int main()
{
            float num;
            cout << "Enter your favorite number: ";
            cin >> num;
            cout<<"\n You have entered "<<num<<endl;
            return 0;
}



2b. Print your number: using a function ( void function with 1 argument passed to it)

#include <iostream>
using namespace std;
                                                    // function prototype
void Print_Your_Number(float);  // this function does not return any values, but expects to
                                                 // receive one floating-point value
int main()
{
  float num;
  cout << "Enter your favorite number: ";
  cin >> num;
  Print_Your_Number(num);   //function call – we are passing one argument to the function
  return 0;
}
                                                               // function definition
void Print_Your_Number( float number) // it’s a good idea to use a different name in the function
{
            cout <<"\nYou have entered "<<number<<endl;
            return;
}




3a. Square your number: sequential

#include <iostream>
using namespace std;
int main()
{
              float num, num_squared;
              cout << "Enter your number: ";
              cin >> num;
              num_squared = num*num;
              cout <<"\nYour number squared is "<<num_squared<<endl;
              return 0;
}



3b. Square your number: using a function (function that receives 1 argument and returns a floating-point value)

#include <iostream>
using namespace std;

float Square_Your_Number(float); //this function receives one floating point value and returns
                                                     //one floating point value to the calling function (main)
int main()
{
              float num, num_squared;
              cout << "Enter your number: ";
              cin >> num;
              num_squared = Square_Your_Number(num);  // assign value returned by the function to num_squared.
              cout <<"\nYour number squared is "<<num_squared<<endl;
              return 0;
}

float Square_Your_Number( float number)
{
             float number_squared;   // need to declare the variable for the result
             number_squared = number * number;
             return number_squared;    //return the result
}



4a. Sum your numbers: sequential

#include <iostream>
using namespace std;

int main()
{
              int num1, num2, sum;
              cout << "Enter two numbers: ";
              cin >> num1 >> num2;
              sum = num1 + num2;
              cout <<"\nThe sum of your numbers is "<<sum<<endl;
              return 0;
}


4b. Sum your numbers: using a function (function that receives 2 integer arguments and returns an integer value)

#include <iostream>
using namespace std;

int Sum_Two_Numbers (int, int);  //function prototype

int main()
{
              int num1, num2, sum;
              cout << "Enter two numbers: ";
              cin >> num1 >> num2;
              sum = Sum_Two_Numbers (num1, num2);  //function call – passing two arguments
              cout <<"\nThe sum of your numbers is "<<sum<<endl;
              return 0;
}

int Sum_Two_Numbers (int number1, int number2)   //function header
{
            int sum_of_numbers;
            sum_of_numbers = number1 + number2;        // function body
            return sum_of_numbers;
}