Default Arguments

C++ allows a function to assign a parameter the default value in case no argument for that parameter is specified in the function call.

Default arguments also called an optional parameter (or) default parameter. Default argument is a function parameter that has a default value provided to it. If the user does not supply a value for this parameter, the default value will be used. If the user does supply a value for the default parameter, the user supplied value is used instead of the default value.

#include<iostream.h>

#include<conio.h>

void display(char ch='a',int i=10,float f=2.56);

void main()

{

clrscr();

display();

display('s');

display('d',20);

display('n',30,4.96);

getch();

}

void display(char ch,int i,float f)

{

cout<<ch<<"   "<<i<<"           "<<f<<"\n"<<"\n";

}

output:

Note:

Once the default value is used for an argument, all the sub sequent arguments must have default values.

int sum( int a, int b=1, int c=6, int d);

It is invalid because c has default value, but d after doesn’t have default value (all default parameters must be the rightmost parameters)