Assignment operator

C provides several assignment operators for abbreviating assignment expressions. For example, the statement

c = c + 3;

can be abbreviated with the addition assignment operator += as

c += 3;

The += operator adds the value of the expression on the right of the operator to the value
of the variable on the left of the operator and stores the result in the variable on the left of
the operator. Any statement of the form

variable = variable operator expression;

where operator is one of the binary operators +, -, *, / or % (or others we’ll discuss in
Chapter 10), can be written in the form

variable operator= expression;