built in and user define functions with examples

functions

A group of statement that together perform a task

Every c++ program has at least one function which is main.

Function consist of name of function return type and parameters

Void main()

Built-in function also called the library functions 

We need not to declare and define these functions because they are already written in c++.

We need to include these functions in program to use

For example #include<iostream> #include<math>

c/c++ allow a programmer to define their own functions

A user defined function groups code to perform a specific task and group of code written by user(programmer)

We need to call the function to use in the program. 

program of user define function:

Example 1:

#include<iostream>

using namespace std;

int sum()

{

    int a,b;

    cout<<"enter value of a "<<endl;

    cin>>a;

    cout<<"enter value of b "<<endl;

    cin>>b;

    cout<<"a+b ="<<a+b<<endl;

}

int main()

{

    sum();

}

user define function : example 2

#include<iostream>

using namespace std;

int sum(int a,int b)

{

    cout<<"a+b ="<<a+b<<endl;

}

int main()

{

    sum(10,67);

}