About Lesson
Expressions such as
x = x + 5
where the variable on the left hand side is used on the right hand side, can be written as
x += 5
The += operator is called an assignment operator.
Most binary operators have a corresponding assignment operator, op=, where op is one of
+ - * / % << >> & ^ |
Note that
x *= y + 1
means
x = x * (y + 1)