C++ Loops (For, While and Do while)

                                                  The for statement

The C++ for statement has the following form:

Syntax:

for  (expression1;Condition;expression2)
	statement;

for  (expression1;Condition;expression2) {
	block of statements
}

expression1 initialises; expression2 is the terminate test; expression3 is the modifier (which may be more than just simple increment);

NOTE: C/C++ basically treats for statements as while type loops

For loop example program:

/*  Example Program For for Loop In C++ Programming Language          */

// Header Files
#include<iostream> 
using namespace std;

//Main Function
int main()
{
     // Variable Declaration
    int x=3;

     //for loop
	for (x=3;x>0;x--)
	{
		cout<<"x="<<x<<endl;
	}
     //Main Function return Statement
     return 0;
}

Output:

x=3
x=2
x=1

                                   The while statement

The while statement is similar to those used in other languages although more can be done with the expression statement -- a standard feature of C.

The while has the form:

Syntax:

while (expression)
	statement;

while (expression)
	block of statements
}

While statement example program

/*  Example Program For while Loop In C++ Programming Language */

// Header Files
#include<iostream> 
using namespace std;

//Main Function
int main()
{
     // Variable Declaration
    int x=3;

     //while loop
	while (x>0)
	{
		cout<<"x="<<x<<endl;
		x--;
	}
 //Main Function return Statement
     return 0;
}

Output:

x=3
x=2
x=1

                          The do-while statement

Syntax:

C's do-while statement has the form:
do {
   statement;
}while (expression);

It is similar to PASCAL's repeat ... until except do while expression is true.

do while Loop example:

/*  Example Program For Do While Loop In C++ Programming Language */

// Header Files
#include<iostream>
using namespace std;

//Main Function
int main()
{
     // Variable Declaration
    int x=3;

     //do while loop
  	 do {
	   cout<<"x="<<x<<endl;
	   x--;
	 }while (x>0);
     //Main Function return Statement
     return 0;
}

outputs:

x=3
x=2
x=1

NOTE: The postfix x- operator which uses the current value of x while printing and then decrements x.