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Variables

Now, we will try another program, which will make it easier for you to change the pin number and the timing. Open blink-variable and upload.

This program does the same thing as the last one, but has some differences. It has the following lines at the top:

int ledpin = 12; int ontime = 500;

The words ledpin and ontime are variables. You could change their names to anything you like, but you have to change it throughout the program. The word int is telling Arduino that these variables are of type integer, so their value can be any integer (whole number). The first line is setting the value of the variable ledpin to 12. This way, you can use the variable name instead of writing 12 throughout the program, like inside digitalWrite().

The second line is setting the value of the variable ontime to 500.

The reason to use variables is that it makes it easy to change. For example, try changing the pin number again, by changing the value of ledpin at the top of the program.

This changes the pins everywhere in the program. So if you had used ledpin in a 100 different places, then you don’t need to change the program in all 100 places just to change the pin. You can do it at the top of the program once!

Try the following as well (make sure to save as blink-variable-mod in your Mod folder first!).

  1. Try changing the ontime variable at the top of the program.
  2. Now create a new variable (call it whatever you want), and use it to make the LED stay ON for one full second, and stay OFF for half a second.

CHECKPOINT!