Difference between Entry Control Loop and Exit Control Loop

Exit Control Loop

An exit-controlled loop is a type of Loop in computer programming that tests the loop condition at the end of the Loop after executing the body of the Loop at least once.

1. As the program flow reaches an exit-controlled loop, the loop body is executed first, and then the loop condition is tested.
2. If the condition is met, the Loop will continue to run, and the body's code will perform again. If it does not, the Loop will exit, and the program will continue execution from the first statement following the Loop.
3. After running the loop for required iterations (when the condition is not met), the program exits the loop.

Do-while loop is primarily used in the exit-controlled Loop.

Example Code

#include <bits/stdc++.h>
using namespace std;

int main(){
	int x=0;
	do{
    	cout<<x<<" ";
    	x++;
	} while (x<10);
	return 0;
}

You can also try this code with Online C++ Compiler

Run Code

Output

Explanation

In the above code, x is initialized with zero, and as the Loop starts, x=0 is printed, and the condition x<10 is checked. So after printing till x=9, x becomes 10. Here the loop condition will fail as x=10 and not x<10, and the Loop will be executed.

This is used when we want to run the instructions in the Loop's body at least once without writing the code explicitly once again before the Loop's code. Hence, we can save our code from redundancy which is the primary reason for using Loops.

Difference between Entry Control Loop and Exit Control Loop

Here, we will see the difference between an Entry Control Loop and an Exit Control Loop:

Also see, AMD vs Intel

Difference in Code

This is where we can see the difference between Entry and exit-controlled loops.  

#include <bits/stdc++.h>
using namespace std;

int main(){
	cout<<"Entry controlled loop: ";
	for (int x = 1; x < 1; x++){
        	cout<<x<<" "; 
	}
	cout<<endl;

	cout<<"Exit controlled loop: ";
	int x=1;
	do{
        	cout<<x<<" ";
        	x++;
	} while (x<1);

	return 0;
}

You can also try this code with Online C++ Compiler

Run Code

Output

Explanation

Here in both Entry and exit loops, x is initialized with 1. Now the terminating condition is x<1 for both. Therefore, the entry loop will not print any output as it first checks the loop condition, but the exit loop will print the value of x as the condition will not be matched. After this, in the exit loop, x becomes 2, greater than 1. Now Loop will be terminated.  

Learn about, Characteristics of OOPS

Frequently Asked Questions

What is an entry-controlled loop?

An entry-controlled loop is a loop where the condition is checked at the beginning of each iteration, and if it is false, the loop body is not executed.

What is an exit-controlled loop?

An exit-controlled loop is a loop where the condition is checked at the end of every iteration, and if it is false, the loop body is not executed.

What is an example of an exit-controlled loop?

A do-while loop is an example of an exit-controlled loop. The loop body executes at least once in a do-while loop, and the condition is checked. If it does not meet, the Loop exits; if it does, the Loop continues executing.

What is an example of an entry-controlled loop?

A while loop is an example of an entry-controlled loop. In a while loop, the loop condition is checked before the loop body executes, and if it is false, the loop body does not run.

Can an entry-controlled loop be converted to an exit-controlled loop and vice versa?

Yes, it is possible to convert an entry-controlled loop to an exit-controlled loop and vice versa by changing the loop condition and the position of the loop body.

Conclusion

In this article, we briefly discussed loops, Entry Control Loops and Exit Control Loops. We also discussed the difference between Entry Control Loop and Exit Control Loop. They mainly differ in the time of checking the loop condition. Programmers need to understand the difference between Entry Controlled Loops and Exit Controlled Loops, as well as when to use each type of Loop, as this can significantly impact the performance and behaviour of their code.

To learn more about Loops, visit our other blogs:

• Loops in Javascript
• Loop Optimization
• Loops in Python

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