Iteration Constructs

The Do-While Loop

Source Code :

// Program Description:
// A Program that uses do-while iteration construct to print a series

#include<iostream.h>
#include<conio.h>

void main()
{
// cleaning the screen
clrscr();


// declaration of variables
int ctr = 0;


// do-while loop starts here
do
{
cout<<endl<<"\t"<<ctr;

Iteration Constructs

The While Loop

Source Code :

// Program Description:
// A Program that uses while iteration construct to print a series

#include<iostream.h>
#include<conio.h>

void main()
{
// cleaning the screen
clrscr();


// declaration of variables
int ctr = 0;


// while loop starts here
while(ctr<=5)
{
cout<<endl<<"\t"<<ctr;
ctr++;

}// while loop ends here


// waiting for the user to analyse the output
cout<<endl<<endl<<"\tPress any key to quit...";
getch();

}// main ends here

Program Flow :

This Iteration Construct is a bit different from the For Iteration Construct because it does not have the Initialising Condition in the Loop statement and the Increment/Decrement Statement is also absent. Instead the Counter Variable is Initialised outside (before) the Loop and the Increment/Decrement statement is present inside the Loop block.

• The Loop Statement checks the Counter's Value with the specified condition.
• If the Condition evaluates to true the compiler enters the Loop's body and executes the whole block and then comes back to the conditional statement and the cycle goes on.
• Once the False condition is met the Compiler exit the Loop and moves on.
• The compiler then waits for the user to press any key to exit.

Output Screenshots :

Iteration Constructs

The For Loop

Source Code :

// Program Description:

// A Program that uses for iteration construct to print a series

#include<iostream.h>

#include<conio.h>

void main()

{

// cleaning the screen

clrscr();

// declaration of variables

int ctr;

// for loop starts here

for(ctr=0;ctr<=10;ctr++)

{

cout<<endl<<"\t"<<ctr;

}// for loop ends here

// waiting for the user to analyse the output

cout<<endl<<endl<<"\tPress any key to quit...";

getch();

}// main ends here

Program Flow :

• A counter variable is created in the memory. This variable's value acts as the termination statement for the loop.
• The Looping Statement is encountered by the compiler. In this statement the compiler checks for the counter variable's initial value to enter the loop.
• If the Loop Condition is fulfilled by the counter variable the block of code which is placed inside the curly braces gets executed.
• The Loop then comes back to the Conditional Statement and checks whether the counter variable's value still fulfills a certain criteria.
• If the value of counter still fulfills the condition the Loop is executed again.
• This process continues until the Counter's value fulfills the condition.
• The Compiler exits the Loop and waits for the user to press a key to exit.

Output Screenshots :

Simple Interest Calculator

Another Basic program to Calculate the Simple Interest

Source Code : 

// Program Description :

// A Program that calculates the simple interest.

#include<iostream.h>

#include<conio.h>

void main()

{

// cleaning the screen

clrscr();

// declaration of variables

double p;    float r,si; int t;

// the input of values

cout<<"Enter the Principal Amount : ";

cin>>p;

cout<<"Enter the Rate of Interest : ";

cin>>r;

cout<<"Enter the Time : ";

cin>>t;

// calculation of simple                       Principal x Rate x Time

// interest using the formula   SI   =   -----------------------------

//                                                                         100

si=(p*r*t)/100;

// display the interest that is to paid

cout<<endl<<"The Interest to be paid is "<<si;

// waiting for the user to analyse the output

cout<<endl<<endl<<"Press any key to quit...";

getch();

}  //main ends here

Program Flow : 

• The message for entering the principal amount is displayed.
• The user enters the principal amount and presses Enter.
• The message for entering the rate of interest is displayed.
• The user enters the rate of interest and presses Enter.
• The message for entering the time period is displayed.
• The user enters the time period and presses Enter.
• The program calculates the Simple Interest using the values provided.
• The Simple Interest is displayed.
• The program waits for user to Press any key to exit.

Output Screenshots : 

Sum of Numbers

This is the most Basic Program of all time - "The sum of two numbers".

Source Code :

// Program Description :
// To calculate the sum of two numbers

#include<iostream.h>
#include<conio.h>

void main()
{
// cleaning the screen
clrscr();


// declaration of variables
float num1,num2,sum;


// input of values
cout<<"Enter the first number : ";
cin>>num1;
cout<<"Enter the second number : ";
cin>>num2;

// calculating the sum of numbers
sum=num1+num2;


// output the sum
cout<<endl<<"The sum of "<<num1<<" and "<<num2<<" is "<<sum<<endl;


// waiting for the user to analyse the output
cout<<endl<<"Press any key to quit...";
getch();

} // main ends here

Program Flow :

• The message for entering the first number is displayed.
• The user enters the number and presses Enter.
• The message for entering the second number is displayed.
• The user enters the second number and presses Enter.
• The program calculates the sum of the numbers.
• The sum of the numbers is displayed.
• The program waits for user to Press any key to exit.

Output Screenshots :