the ability to access an arbitrary element of a sequence in equal time or
any datum from a population of addressable elements roughly as easily and
efficiently as any other, no matter how many elements may be in the set. In
computer science it is typically contrasted to sequential access which
requires data to be retrieved in the order it was stored.
A typical illustration of this distinction is to compare an ancient scroll
(sequential; all material prior to the data needed must be unrolled) and the
book (direct: can be immediately flipped open to any arbitrary page). A more
modern example is a cassette tape (sequential — one must fast forward through
earlier songs to get to later ones) and a CD (direct access — one can skip to
the track wanted, knowing that it would be the one retrieved).
