Comments are lines in the program that are used to inform yourself or others about the way the program works. They are ignored by the compiler, and not exported to the processor, so they don’t take up any space in the microcontroller’s flash memory. Comments' only purpose is to help you understand (or remember), or to inform others about how your program works.
A single line comment begins with
// (two adjacent slashes). This comment ends automatically at the end of a line. Whatever follows
// till the end of a line will be ignored by the compiler.
There are two different ways of marking a line as a comment:
// pin 13 has an LED connected on most Arduino boards. // give it a name: int led = 13; digitalWrite(led, HIGH); // turn the LED on (HIGH is the voltage level)
Notes and Warnings
When experimenting with code, "commenting out" parts of your program is a convenient way to remove lines that may be buggy. This leaves the lines in the code, but turns them into comments, so the compiler just ignores them. This can be especially useful when trying to locate a problem, or when a program refuses to compile and the compiler error is cryptic or unhelpful.