Since its origin, const has taken
on a number of different purposes. In the meantime it trickled back into the C
language where its meaning was changed. All this can seem a bit confusing at
first, and in this chapter you’ll learn when, why, and how to use the
const keyword. At the end there’s a discussion of volatile,
which is a near cousin to const (because they both concern change) and
has identical syntax.
The first motivation for const
seems to have been to eliminate the use of preprocessor #defines for
value substitution. It has since been put to use for pointers, function
arguments, return types, class objects and member functions. All of these have
slightly different but conceptually compatible meanings and will be looked at in
separate sections in this
chapter.
