Comma Operator
The comma operator is used to string together various expressions. Essentially, the comma causes a sequence of operations to be performed. Whenever it is used on the right side of the assignment statement, the final expression of the comma-separated list is the value assigned to the expression.
Example:
y= 10;
x = (y- = 5, 25 / y);
After execution, x will have the value 5 since y's original value is reduced through 5, and then that value is divided into 25, yielding 5 as the result.