We report on a number of coding problems that occur frequently in
published \textsc{CALGO} software and are still appearing in new
algorithm submissions.  Using Algorithm 639 as an extended example, we
describe how these types of faults may be almost entirely eliminated
using available commercial compilers and software tools.  We consider
the levels of testing required to instil confidence that code performs
reliably.  Finally, we look at how the source code may be
re-engineered, and thus made more maintainable, by taking account of
advances in hardware and language development.