Call by reference is an important technique in C++ programming era. This technique has various forms such as,
- Passing by value,
- Passing by Independent Reference,
- Passing by Return reference,
For all the above methods, we have a sample C++ program. Feel free to check it out below. All free source codes are there 
Passing Value using Call by reference in C++:
C++ program on “Passing Value using Call by reference in C++“. It will perform a reference operation for the given variable and passing the values. This CPP program can be used for all kind of students for their lab exams and related tests. It may be useful for their exam purpose.
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/*
Title: Swapping in Call by reference
Author: Karthikh Venkat
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This website provides lots of useful information for all students.
*/
//Header Files.
#include<iostream.h>
#include<conio.h>
void neg(int *k);
int main()
{
clrscr();
int a;
a = 20;
cout << x << "Negated is ";
neg(&a);
cout << x << "\n";
getch();
return 0;
}
void neg(int *k)
{
*k = -*k;
}
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Independent Reference Program in Call by reference:
// Header files
#include<iostream.h>
#include<conio.h>
int main()
{
clrscr();
int x; //Variable
int &ref = x; //Independent reference
x = 20;
cout << x << " " << ref << "\n";
ref = 100;
cout << x << " " << ref << "\n";
int y = 19;
ref = y; // This puts y's value into x
cout << x << " " << ref << "\n";
ref--; // this decrements a
// it doesn't affect what ref variable refers to
cout << x << " " << ref << "\n";
getch();
return 0;
}
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CALL BY REFRENCE USING RETURN REFERENCE PROGRAM:
// Header files
#include<iostream.h>
#include<conio.h>
char &replace(int k); // Return a reference
char a[80] = "Hi Everyone";
int main()
{
clrscr();
replace(5) = 'Y'; // Assign Y to space after Hi
cout << a;
getch();
return 0;
}
char &replace(int k)
{
return s[k];
}