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do-while

Let’s get a little complex now. We will talk about loops here. Loops, in another word, are iterations. There are three types of loops that we will focus on. First, let’s take a look at the do-while statements.

do-while statements ask the program to do certain tasks repeatedly while a condition is met. When the condition is false, the program will run the tasks once and does not repeat.

For example, have the program calculate addition between two numbers. Ask the user if he wants to calculate another problem. Do the addition repeated while the user answers y.

#include <iostream.h>
int main()
{
    char YorN;
do{
    int FirstInteger, SecondInteger;
    cout << "Enter an integer: ";
    cin >> FirstInteger;
     cout << "Enter another integer: ";
    cin >> SecondInteger;
    cout << "The sum is " << FirstInteger + SecondInteger << endl;
    cout << "Do you want to calculate another addition problem?"
    cin >> YorN;
}while(YorN = = ‘Y’);
    return(0);
}

while

Another type of loop that is used is the while statement. How is it different from the do-while statement? Well, in the do-while statement, the tasks within that statement are performed at least once. In the while statement, the condition MUST be met, before the tasks can be done. If after performing the tasks, the result still meets the condition of the while statement, the tasks are repeated using the result.

Let’s have the program ask the user to enter a number less than or equal to 100. While the number is greater than 100, display "The number is too large. Try again." Then, have the user enter the number again. The loop will repeat as long as the user keeps entering a number greater than 100. If the user enters a number less than or equal to 100, the loop will terminate. The while statement will be skipped if the user enters a number less than or equal than 100 in the first place. Here’s the code for the program:

#include <iostream.h>

int main()

{

    int Number;

    cout << "Enter a number less than or equal to 100: ";

    cin >> Number;

    while(Number > 100){

            cout << "The number is too large. Try again.";

            cin >> Number;

     }

     return(0);

}

for

Now you already have a taste of what loops are like. We will introduce you to a new type of loop called the for loop. In a for loop, you can specify the number of times you want the loop to iterate.

Here’s the format to set up the for loop:

for(start; condition; increment/decrement)

assignment statements;

Let’s create our own for loop that displays all the numbers from 5 to 16.

for(int x = 5; x <=16; x++)

cout << x << endl;

Above we initiated the variable x with 5. The loop will repeat as long as x is less than or equal to 16. x increments by one each time. Thus, the numbers 5 to 16 are displayed on the screen.

Break Statements

Do you recall the break statement from the switch statements? If you want to put an end to a certain section of the code in your program, or if you want to terminate a loop, you can add in a break statement.

All you need to do is type break; within the section of the code that you want to end.

For example, you suddenly want to stop the program. It requires you to press q to quit. When you press q, the programmer could probably have put a break statement in the code so that you can terminate the program. Let’s take a look at the code:

char Key;

cout << "Press any key to calculate, or q to quit the program.";

cin >> Key;

while(Key != ‘q’){

     cout << "Press any key to start calculating or q to quit.";

     cin >> Key;

     if(Key = = ‘q’)

             break;

     int Number, Number2;

     cout << "Enter a number: ";

     cin >> Number;

     cout << "Enter another number: ";

     cin >> Number2;

      cout << "The sum of the two numbers is " << Number + Number2

               << endl;
}

Algorithms

We all want to make life easier, even programmers do. Before touching upon anything complex, it is always good to have a plan at hand. In C++, such a plan is called an algorithm. An algorithm consists of the procedures to write the code. It is like a rough draft of the code for the program. If you list out your procedures with words and C++ code, that type of algorithm is a pseudocode.

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