Abstract
Passing data to a function is very important and is often used at times in writing the code.
- There are two ways to pass data to the function in C/C++.
- Pass-By-Value.
- Pass-By-Reference.
Scope of the Article
- This article will provide you with a basic to intermediate level of understanding of how to pass data to the function.
- Covers the concepts like Call-By-Value & Call-By-Reference using code snippets in C/C++.
Note
For the scope of this article, we will use Call-By-Value and Pass-By-Value interchangeably similar is the case for Call-By-Reference and Pass-By-Reference. You can learn more about the differences here.
Prerequisites
- One should have a basic understanding of C/C++.
- How to make Functions in C/C++ with a variable number of arguments.
- How to pass different parameters to the function.
Now, If You Know the Prerequisites, you can move forward.
Pass-By-Value
- Pass by value is when a function copies the actual value of an argument into a formal parameter of the function.
- Changes made to the parameter in the function have no effect on the argument after the function call ends.
- In Simpler terms, we can say that changes made to the variable passed by value to the respective function will only reflect in the particular scope of that function.
- Let's look at a few examples to clarify this.
Example Code 1
#include<bits/stdc++.h>
void add(int x,int y)
{
x=x+y;
return;
}
int main()
{
int x=5;
int y=6;
add(x,y); // passing by value the parameters (x,y).
cout<<x<<"\n";
return 0;What do you think the value of x will be?
A.) 5
B.) 11
Notice one thing carefully: we have passed the parameters x and y with value. Meaning the add function only has a copy of their value, not the memory address.
So the update of (x=x+y) has a local scope inside the add function only. After the function call ends, the value of variable x will be the same as the previous, i.e., 5.
Example Code 2
#include<bits/stdc++.h>
using namespace std;
void swapValues(int x,int y)
{
swap(x,y);
return;
}
int main()
{
int x=5;
int y=6;
swapValues(x,y); // passing by value the parameters (x,y).
cout<<x<<"\n";
return 0;
}
When to use Pass-By-Value
- When we want to calculate the value of a particular function without modifying the values of arguments passed.
- To avoid bugs caused due to memory stack issues.
Pass-By-Reference
- Pass by reference copies the address of an argument into the formal parameter.
- The address is used to access the actual argument used in the call.
- This means the changes made to the parameter affect the passed argument.
Example Code
#include<bits/stdc++.h>
using namespace std;
// Taking the values of x and y with reference.
void swapValues(int &x,int &y)
{
swap(x,y);
return;
}
int main()
{
int x=5;
int y=6;
swapValues(x,y); // passing by reference the parameters (x,y).
cout<<x<<"\n";
return 0;
}
Here notice one thing carefully: we have taken the values of x and y using the ampersand operator (&), meaning we are taking values by reference using the actual memory address of the variables.
So after the function calls end. The value of x will be swapped with the value of y.
When to use Pass-By-Reference
- Whenever you want to store the modified value of a variable after the function call ends.
- If you need to update the value of some variable in a recursive function.
Time Complexity
The time complexity of programs using pass-by-value or pass-by-reference is almost similar.
Key Points and Conclusion
- Both are equally important features of C/C++ pass-by-value and are mostly used over pass-by-reference.
- A copy of the same variable is stored in the call stack during the function call.
- As per the needs of the program, the choice between pass-by-value and pass-by-reference has to be made.
Thank you so much for reading this!
The featured image is taken from here.