Counting Loops

A for loop repeats a block of code, but it’s more configurable than a while loop. A for loop is also the preferred tool for counting tasks.  while loops are better for repeating something “while” a condition is true.  In contrast, for loops are better for repeating a block a certain number of times.  This next program counts to ten with a for loop.

  • Click SimpleIDE’s Open Project button.
  • If you’re not already there, navigate to ...\SimpleIDE\Learn\Examples\C Intro\Basics.
  • Open Count to Ten.side.
  • Set the power switch to position 1 if it isn't already (if applicable for your board).
  • Click the Run with Terminal button, and verify that the program counts to ten.
/*
  Count to Ten.c
 
  Count to ten in SimpleIDE Terminal.
*/

#include "simpletools.h"                      // Include simpletools

int main()                                    // main function
{
  for(int n = 1; n <= 10; n++)                // Count to ten
  {
    print("n = %d\n", n);                     // Display name & value of n
    pause(500);                               // 0.5 s between reps
  }
  print("All done!");                         // Display all done
}

 

How it Works

The for statement has three parameters: for(start index; condition; increment).    

  • start index – typically a variable that is assigned an initial value where the counting starts
  • condition – a condition that has to be true for the loop to repeat
  • increment – an operation that should be performed on the index variable with each loop repetition

In the Count to Ten program, the start index is int n = 1, a variable declaration that initializes the variable n to the value 1.  The condition is n <= 10, which means that the loop will keep repeating while n is less than or equal to ten.  The increment is n++, which is a shorthand form of n = n + 1.  So with each repetition of the for loop’s code block, the value of n increases by 1.

 

Did You Know?

Increment operators — The ++ operator is called an increment operator.  Although increment and decrement operators are especially useful in for loops, they can be used as shortcuts in many parts of your programs. 

++    add 1 to a variable
––    subtract 1 from a variable

Assignment operators — There are also some useful shortcuts for assigning values to variables.  For example, instead of n = n + 5, you can use n += 5. As you might expect there are, shortcuts for subtraction  –=, multiplication *=, division /=, and modulus (remainder) %=. These are called the assignment forms of the operators.

 

Try This

Here is a for loop that will count to 200 in steps of 5, just like the while loop you experimented with earlier.

  • Use Save Project As to save your program as Count to 200 by 5s.
  • Modify the for loop so that it looks like the this:

  • Verify that it counts to 200 in steps of 5.

 

Your Turn

  • Modify your program so that it counts up to 200 in steps of 5, then down to 0 in steps of 10.