Functions in C++

⋮

A function is a group of statements that is executed when it is called from some point of the program

Syntax for defining a Function

datatype functionname ( parameter1, parameter2, ...) 

{ 

Statements;

 }

Where:

- datatype is the type of the value returned by the function.

- name is the identifier by which the function can be called.

- parameters (as many as needed):   The purpose of parameters is to allow passing arguments to the function from the location where it is called from.

- statements is the function's body. It is a block of statements surrounded by braces { } that specify what the function actually does.


Advantages of using functions

  •  Dividing a  large program into small functions
  •  It is possible to reduce the size of a program by calling and using them at different places in the program

  •  When the function is called, control is transferred to the first statement in the function body.
  •  Debugging will be easy
  •  Easy to read 


The main() function 

 main() function is the starting point for the execution of a program

void main()

{


}

Steps to Use functions in c++

  • Declare a function (Function Prototyping)
  • Define a function
  • Call the function

Step 1: Declare the function (Function prototyping)

Function prototyping is a declaration statement and describes the function interface to the compiler by giving details such as number of parameters, data type of parameters/arguments and the type of return values

Example

float add(int x, int y);

Step 2: Define a function

Statements can be defined in this step using the following syntax

Syntax


Datatype function_name(parameter_list)

{

Statements;

}


Example

float add(int x,int y)

{

Statements;

}

Step 3: Calling the function

Statements can be defined in this step using the following syntax

If no return type -> add(10,20);

If return type-> float k=add(10,20);

TYPES OF PASSING PARAMETERS IN FUNCTIONS

  • Function without parameters and without return type
  • Function with parameters and without return type
  • Function without parameters and with return type
  • Function with parameters and with return type

 Example 1:

In this example, the function is used to add two values, without parameters and no return type

# include <iostream.h>

#include <conio.h>

void add();     //declaration

void add()      //define a function

{

    int a,b,c;

    a=10; 

    b=20;

        c=a+b;

     cout<<“Answer=“<<c;

}

void main()

{

add();    //calling

}

 Example 2:
In this example, the function is used to add two values, with parameters and no return type
# include <iostream.h>
#include <conio.h>
void add(int m, int n);     //declaration

void add(int m, int n)      //define a function
{
     int c;
    c=m+n;
    cout<<“Answer=“<<c;
}

void main()
{
int a,b;
a=30; b=40;
add(a,b);    //calling
}

Example 3:

In this example, the function is used to add two values, without parameters and with return type
# include <iostream.h>
#include <conio.h>
int add();     //declaration

int add()      //define a function
{
    int a,b,c;
    a=10; 
    b=20;
     c=a+b;
     return ( c );
}
void main()
{
int ans;
ans=  add();    //calling
cout<<“Answer=“<<ans;
}

Example 4:

In this example, the function is used to add two values, with parameters and with return type

# include <iostream.h>
#include <conio.h>
int add(int m,int n);     //declaration

int add(int m,int n)      //define a function
{
    int c;
 
     c=m+n;
     return ( c );
}
void main()
{
int ans,a,b;
a=10; b=20;
ans=  add(a,b);    //calling
cout<<“Answer=“<<ans;
}

Inline function
 If a function is inline, the compiler places a copy of the code at that point itself where the function is called

 To inline a function, place the keyword inline before the function name and define the function

Example
inline void add()
{
   int a,b,c;
   a=10;
   b=20;
   c=a+b;
   cout<<c;
}

void main()
{
add();
}



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