Any expression followed by a semicolon forms an expression statement:

<expression>;

The compiler executes an expression statement by evaluating the expression. All side effects from this evaluation are completed before the next statement is executed. Most expression statements are assignment statements or function calls 

The null statement is a special case, consisting of a single semicolon (;). The null statement does nothing, and is therefore useful in situations where C++ syntax expects a statement but your program does not need one.