Programming for the Arduino - Arduino Sketches: Tools and Techniques for Programming Wizardry - page 38

Control Structures
The power of microprocessors and microcontrollers is their ability to process
data. They follow instructions, and can also execute conditional instruction
depending on data. Does the variable contain a number greater or equal than
42? If so, execute this portion of code. Otherwise, execute another portion. These
instructions come in the form of conditional statements like if , for , and while .
if Statement
The if statement is the simplest of branching statements and is used to detect
if an expression is equal to a result. It is used as follows:
if (expression)
{
statement;
}
Multiple instructions can be used inside an if statement, by placing multiple
instructions inside curly brackets:
if (expression)
{
statement;
another_statement;
}
It is also possible to execute two sets of instructions using an if .. else state-
ment. You can think of it as doing one thing if the result is equal to something,
else performs another action.
if (expression)
{
do_this;
}
else
{
do_that;
}
It is also possible to mix several if s using else :
if (expression)
{
do_this;
}
else if (expression)
{
do_that;
}