while

Loops through the statements enclosed within the { code block } until the test_expression is false:

 

while (test_expression) {
statements ;
}

 

#include <iostream>
using namespace std ;

int main () {

	int myVar ;

	while (myVar < 5){

		cout << "myVar is now: " << myVar << endl ;

		myVar++ ;
	}

	return 0;
}

Compile & Run:

myVar is now: 0
myVar is now: 1
myVar is now: 2
myVar is now: 3
myVar is now: 4

 

*Note: interestingly, the compiler set the uninitialised myVar to 0.

However, this is bad programming practice and in reality should be defined.

 

Also note, it is possible to simply treat myVar as a boolean in the while test parentheses:

#include <iostream>
using namespace std ;

int main () {

	int myVar = 5;

	while (myVar){

		cout << "myVar is now: " << myVar << endl ;

		--myVar ;
	}

	return 0;
}

Compile & Run:

myVar is now: 5
myVar is now: 4
myVar is now: 3
myVar is now: 2
myVar is now: 1

 

 

Line 8  could have been written as while (myVar > 0) { but since it decrements to 0, and 0 is the same thing as FALSE, it is possible to simply treat myVar as a boolean in this case.

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