Updated April 13, 2023
Introduction to Call by Value in C++
Call by value is a method in C++ that is used for passing some parameters or arguments to the function which copies the original values of the function to the passed parameters. Changes made to the parameters inside the function have no effect on the passed parameters which means by default C++ call by value method is used for calling arguments that cannot be altered continuously. Any function present within the code cannot change the values passed to the main function. The values can be altered that too after passing parameters outside the main function.
Syntax
There is no syntax but there is a way to create a function and simultaneous calling happens with the function:
int main()
{
int dt = 9;
func_test (dt); // Calling function with the value.
return 0;
}
void func_test(int dt) // Declaring the function.
{
dt= 8;
}Explanation:
void func_test(): represents the syntax for the creation of the function and then it passes the formal parameter int it to the function.
int main(): represents the main function which calls the func_test and then initializes the value.
How does Call by Value work in C++?
Call by value and call by reference are the two types of calling functions frequently used by most of the programmers and creates a misconception which is very much needed to be clear. Calling a function by value needs some value to be passed as a copying function and then it is known for calling the values for that function.
Call by value method passes argument as a copy of the formal parameter passed within the function. But the arguments passed have some effect on the function which says that changes made in a copy of the variable do not hamper and do not modify the value of variable outside function. Actual and the formal parameters passed to the function does not alter the value and passes values of the variables using a very simple and direct method.
Moreover, the actual or say the original value never gets hampered or changed. But a question which comes in mind is then where these arguments being passed or how does it function with the memory management techniques. Actual and formal parameters get created at different memory locations with the different locations having different privileges for accessing the parameters or the function.
Taking into consideration the safety of the function and call by value method then it is much safer than call by reference with respect to the parameters as these actual parameters do not get changed or altered even accidentally. C++ values when called by programming languages like C++, PHP, etc. come by its default values and never gets transformed or changed frequently. But the totally opposite situation happens with the call by reference where the values or the arguments passed gets changed with different types of values and transformations.
There the original value gets altered and can be modified with which it can be easily said that call by reference method is less safe compared to the call by value method in C++. Incall by reference when compared with the call by value and the memory allocation the memory will get allocated at the run time of executing the method.
External pointer variables are needed to be created to store the address of the variables which are declared and defined for execution. Unlike call by value method call by reference passes a variable itself no need to create any external formal parameter to pass values and then check. It is very much needed to keep an important point in mind which means that the parameters changes inside the function should not get reflected outside the function while passing actual parameters.
Examples to Implement Call by Value in C++
Below are the examples mentioned:
Example #1
This program illustrates the use of call by value method by calling the values and assigning the values and is then called by the function at the time of execution. One swapper function Is created and then the function is called which gives the output by swapping the values as shown in the output.
Code:
#include<iostream>
using namespace std;
void swapper(int m, int n) {
int z;
z = m;
m=n;
n=z;
}
int main()
{
int m = 20, n = 21;
cout<<"before_swap: "<<m<<","<<n<<endl;
swapper(m,n);
cout<<"after_swap: "<<n<<","<<m; return 0;
}Output:
Example #2
This program represents the call by reference method which gives a clear picture when compared with the call by value method the mere differences for better understanding of comparisons made.
Code:
#include <iostream>
using namespace std;
void swapper(int &x, int &y);
int main ()
{
int i = 50;
int j = 80;
cout << "swapped_value_before, value of i: " << i << endl;
cout << "After_swapped_value, value of j: " << j << endl;
swap(i, j);
cout << "After_swaping_value, value of i: " << i << endl;
cout << "After_swapping_values, value of j: " << j << endl;
return 0;
}Output:
Advantages of Call by Value in C++
Below are the advantages mentioned:
- Every function has its advantages and disadvantages associated with it so in the case with a call by value method the major advantages are as follows:
- The method containing the data does not get altered as the parameters passed are not having the privilege to change the values.
- When the function is called the actual or the formal parameters passed do not get changed which means that the change is not hampering the functionality.
- The most interesting advantage is that the actual argument passed to the function does not really make a change in any of the formal parameters which in this way does not make much difference.
- It provides security and a safer means to the programmers by making the overall function and its data preserved from any of the security breaches.
Conclusion
Call by value method in C++ plays a very important role in any programming language as it is a frequent activity to make use of this method as part of the daily code base. It provides programmers the flexibility of reusability and time flexibility as most programs get supported by default by the programmers.
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