Inline functions, C++ provides inline functions to help reduce function_call overhead especially for small functions. The

qualifier inline before function's return type in the function informs the computer to generate a copy of the functions code in place, to avoid a function call.

The disadvantage is that multiple copies of function code are inserted in the program (thus making it larger) rather than a single copy of the function to which control is passed each time the function is called.
The compiler can ignore the inline qualifier especially for large functions

Example:

Write a C++ program that prompts for the radius of a circle, and which is passed to an inline function to compute and return the area of a circle. Your program then displays the computed value.

#include 

#include 
#include 
using namespace std;

inline double computearea(int);
int main()

{

int radius; 

double area;

cout<<"Enter the radius of the circle"<>radius;

area=computearea(radius);

cout<<"The area of the circle is:"

<return  0;

}

double computearea(int r)
{

const float    PI=3.142;
      return PI*pow(r,2);
 }