Last Updated on March 28, 2023 by Prepbytes
Iterative statements are used in programs to repeat a section of code. While and do while are iterative statements found in C, C++, Java, and other programming languages. Iterative statements are another name for looping statements. We will discuss the loop, while loop, do-while loop, and the difference between while and do-while loops.
Loop
A loop’s definition in computer programming is similar to its meaning. Loops are a block of code that executes multiple times. If there were no loops, you would have to write everything you wanted to print repeatedly. A Loop repeats the sequence of statements until the stated condition is false. The loop’s purpose is to repeatedly execute the same code.
While Loop
A while loop is a control flow statement that allows code to be executed multiple times based on a specified Boolean condition. A loop consists of two components: the loop body and the control statement. The control statement is a set of conditions that instructs the loop’s body to continue running until the specified condition is met. The while loop is similar to a looping if statement.
We check the condition at the beginning of the loop structure in this loop. A code block will run until the condition is true, at which point the loop will be terminated or ended. We call it an infinite loop if the condition remains true.
A While loop is the most basic looping structure. It is a loop with an entry control. A while loop evaluates a condition before processing the loop’s body. If a condition is true, the body of a loop is executed, and only then.
After the body of a loop is completed, the control returns to the beginning, and the condition is checked. If it is true, the same procedure is followed until the condition is false. When the condition is false, the control exits the loop.
If the condition in a while loop is not true, the body of the loop will not be executed, not even once.
Syntax of While Loop
while (boolean condition)
{
loop statements...
}Flowchart of While Loop
Example of While Loop
Below we have code implementation and explanation of While loop.
#include <iostream>
using namespace std;
int main() {
int count = 1;
while(count<=5)
{
cout<<count<<" ";
count+=1;
}
return 0;
} Output
1 2 3 4 5Explanation
This while loop repeatedly executes the block of code inside it as long as the condition count <= 5 is true. The variable count starts at 1, and each time the loop executes, it prints the current value of the count and increments it by 1. This continues until the count reaches 6, at which point the loop terminates.
Do-While Loop
A Do-while loop is similar to a while loop with the exception that the condition is always executed after the loop body. It’s also known as an exit-controlled loop.
The body of a loop is always executed at least once in the do-while loop. It checks the condition after the body has been executed. If the condition is met, the body of the loop will be executed once more. Otherwise, control is removed from the loop.
Syntax of Do-While Loop
do
{
statements..
}
while (condition);Flowchart of Do-While Loop
Example of the Do-While Loop
Below we have code implementation and explanation of do While loop
#include <iostream>
using namespace std;
int main() {
int i = 1;
do {
cout << i << endl;
i++;
} while (i <= 5);
return 0;
}
Output
1
2
3
4
5Explanation
In the above c++ program , this do-while loop count from 1 to 5, printing each number as it goes. The loop is executed at least once, regardless of the condition. Once i reaches 6, the loop terminates, and the program proceeds to the next step.
Difference between While and Do-While Loop
Here we have the difference between while and do while loop
| While | Do While |
|---|---|
| In while loop condition is checked first and then the statement is executed | In do-while statement is executed at least once thereafter condition is checked |
| It follows top-down approach | It follows bottom-up approach |
| For single statement, we do need to add brackets | In do white brackets are always needed |
| While loop is entry controlled loop | Do while is an exit controlled loop |
| Here “while” keyword is used | Here “do while” keyword is used |
| If the condition is false initially, the loop body is never executed | The loop body is executed at least once, regardless of the initial condition |
Conclusion
A loop is a programming construct that allows the execution of a set of statements repeatedly until a certain condition is met. While loops and do-while loops are two common types of loops in programming. While loops only run the loop body if the loop condition is true, do-while loops run the loop body at least once before checking the loop condition. While loops are useful when you want to repeat a block of code based on a condition, do-while loops are useful when you want to execute the loop body at least once regardless of the initial condition, and then loop as long as a certain condition is true.
Frequently Asked Questions
Here are the FAQ:
Q1. How can I exit a while loop or a do-while loop?
Ans. You can exit a while loop or a do-while loop using the break statement. The break statement immediately terminates the loop and transfers control to the statement that follows the loop. Alternatively, you can use a flag variable to control the loop and set its value to false to exit the loop.
Q2. Can a while loop or a do-while loop contain nested loops?
Ans. Yes, a while loop or a do-while loop can contain nested loops, just like any other type of loop. This allows you to execute more complex code that requires multiple iterations.
Q3. Can a while loop or a do-while loop be used for iterating over collections?
Ans. Yes, a while loop or a do-while loop can be used for iterating over collections, such as arrays or lists. However, it may be more convenient to use a for loop or a for-each loop, depending on the language and the data structure being used.
Q4. What are some common mistakes to avoid when using while loops or do-while loops?
Ans. Some common mistakes to avoid when using while loops or do-while loops include forgetting to update the loop variable, which can result in an infinite loop; using the wrong comparison operator or logic in the condition, which can lead to unexpected results; and not initializing variables properly, which can cause errors or bugs. It is important to test and debug your code thoroughly to ensure that the loop behaves as intended.
Q5. What is the difference between while and do while loop?
Ans. The main difference between a while loop and a do-while loop is that the code inside a while loop may never be executed if the condition is initially false, whereas the code inside a do-while loop is always executed at least once.
Q6. When should I use a while loop, and when should I use a do-while loop?
Ans. You should use a while loop when you want to execute a block of code zero or more times, depending on a condition. You should use a do-while loop when you want to execute a block of code at least once, and then continue executing it zero or more times, depending on a condition.