Notice: This page requires JavaScript to function properly.
Please enable JavaScript in your browser settings or update your browser.Do...while Loop | Introduction to Program Flow
C++ Introduction
course content

Course Content

C++ Introduction

C++ Introduction

1. Getting Started
Why to Learn C++What is C++Entry Point of a ProgramStandard Library and FilesPreprocessor DirectivesThe First Program
2. Variables and Data Types
Data TypesUnderstanding VariablesNumerical Data TypesIntroduction to StringIntroduction to ArraysKeywords sizeof(), auto and typedefWorking with the Array
3. Introduction to Operators
Simple OperatorsA Little MathLogical OperatorsCompound Assignment OperatorPracticing Math Basics
4. Introduction to Program Flow
If...else StatementTernary OperatorSwitch StatementWhile LoopDo...while LoopFor LoopFibonacci Number with Loops
5. Introduction to Functions
What are Functions?Type of FunctionsReturn Statement in FunctionsFunctions With Arguments Simple Function

bookDo...while Loop

Unlike a while loop, which may never execute, a do...while loop is guaranteed to execute at least once. Structure of do…while loop:

Note

The line containing the while part ends with a semicolon (;)

Now let's compare the while and do…while loops.

The while loop:

cpp

main

copy

              
1234567891011121314

            
#include <iostream>

int main()
{
	int variable = 0;

	//loop never executed
	while (variable == 1)
	{
		std::cout << "Hello, I am while loop!" << std::endl;
	}

	std::cout << "While loop didn't start :(" << std::endl;
}

The do...while loop:

cpp

main

copy

              
123456789101112131415161718

            
#include <iostream>

int main()
{
	int variable = 0;

	do
  	{
		// this line is guaranteed to be execute at least once
		std::cout << "Hello, I am Do-Block!" << std::endl; 
	}

	while (variable == 5); // loop continuation condition

	std::cout << "Variable doesn`t equal 5, ";
	std::cout << "so the loop didn't work, "; 
	std::cout << "only the do-block." << std::endl;
}

The do...while loop executed one time when the while loop would never have executed.

Everything was clear?

How can we improve it?

Thanks for your feedback!

Section 4. Chapter 5
some-alt