We must understand the variables in the Arduino program first, because in programming on Arduino a lot of variables are used. Variables are used to store and retrieve data in the form of numbers or characters contained therein. A variable is a way to name and store a value to be used in the program, such as data from a sensor or a temporary value in a calculation in the program. The variable to be used must be declared first. When you declare a variable you define the type of the variable and you may also assign an initial value to that variable.
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