Loops

Loops are used to repeat a block of code. Being able to have your program repeatedly execute a block of code is one of the most basic but useful tasks in programming — many programs or websites that produce extremely complex output (such as a message board) are really only executing a single task many times.

FOR – for loops are the most useful type. The syntax for a for loop is:

For (variable initialization; condition; variable update) {
  Code to execute while the condition is true
}

The variable initialization allows you to either declare a variable and give it a value or give a value to an already existing variable. Second, the condition tells the program that while the conditional expression is true the loop should continue to repeat itself.

 

WHILE – WHILE loops are very simple. The basic structure is

while (condition) {Code to execute while the condition is true} the true represents a Boolean expression. It can be any combination of Boolean statements that are legal.) Notice that a while loop is the same as a for loop without the initialization and update sections. However, an empty condition is not legal for a while loop as it is with a for loop.

Example:

#include <iostream>

Using namespace std; // So we can see cout and endl

int main()
{ 
  int x = 0;  // Don't forget to declare variables
  
  while ( x < 10 ) { // While x is less than 10 
    cout<< x <<endl;
    x++;             // Update x so the condition can be met eventually
  }
  cin.get();
}

Here is an example of a program which has loops (factorial calculator):

/* Source code to find factorial of a number. */
#include <iostream>
using namespace std;
int main()
{
  int x , factorial=1;

    cout << "Please enter a non-negative number:  " << endl;
    cin >> x;

    for(int a=1; a<=x; a++)//HERE IS THE "FOR" LOOP
    {
        factorial=factorial*a;
    }

cout << "The factorial of your number is " << factorial << endl;
cout << "Would you like to play again?   ";
string answer;
cin >> answer;

do
{
    int x , factorial=1;

    cout << "Please enter a non-negative number:  " << endl;
    cin >> x;

    for(int a=1;a<=x;a++)//HERE IS THE "FOR" LOOP
    {
        factorial=factorial*a;
    }

    cout << "The factorial of your number is " << factorial << endl;
    cout << "Would you like to play again  ? ";
    cin >> answer;

}while (answer =="yes");//HERE IS THE "WHILE" LOOP

if (answer== "no")
{
  cout << "AS YOU WISH MASTER, MAY THE FORCE BE WITH YOU! " << endl;
}

return 0;
}

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-The Admin.

CC BY 4.0 Using Loops FOR and WHILE by esaupreciado is licensed under a Creative Commons Attribution 4.0 International License.