I am privileged to have the opportunity to edit this 27th volume of the Advances in Computers series. These books are well known and highly
regarded in the computer field; the series has now been in existence, unbroken,
for most of the lifetime of the entire field—an impressive record indeed. The
volumes have played a significant role in bringing together in one place many
different aspects of the computer and information fields. In fact, many of the
articles have become standard references, and, in spite of the everchanging
nature of the field, many of them continue to be of value. Throughout the
existence of this series, which dates from 1960, we have experienced great
expansion and dynamic change in computers, their uses, and their
applications. This series has been a part of this dramatic development and perhaps
has even been responsible for some of it.