A sequence point is any point in a program’s execution wherein all side effects of previous evaluations are complete and no side effects of subsequent evaluations have started. If you want, you can think of the semicolon at the end of each statement as a sequence point. A side effect is an action that changes [...]

Indexing the array elements occurs with the standard array operator [], but additionally the class checks for boundary
overflow. Furthermore, the array operator is interesting in that it both produces a value and accepts a value, when
used, respectively, as a right-hand value and a left-hand value in expressions.
An example of the use of the class is [...]

Any type can be qualified by the type qualifiers const or volatile.In simple declarations, the type qualifier is simply another keyword in the type name, along with the basic type and the storage class.
Syntax for the const and volatile keywords

int * volatile x; /* x is a volatile pointer to an int [...]