What is a bug?

In computing parlance, unlike normal life, bugs and viruses have nothing to do with each other. A bug is simply a fault, or error, while a virus is a malicious program that propagates from computer to computer by hiding itself inside another program or document. Legend has it that the term bug was invented by […]

Spreadsheet error rates

Think about it for a moment. Do 10% of spreadsheets contain errors? Or 20% (for the pessimists among you)? These rates are high, and should be enough to make alarm bells ring, but the actual rates are probably far higher. A few years ago Professor Ray Panko, at the University of Hawaii, pulled together the […]

The true significance of bugs in spreadsheets

There are many reports of extremely high occurrence rates for bugs in spreadsheets. From reading them, you might think that very few spreadsheets are error-free. However, many people who are aware of the likelihood of errors in spreadsheets go to great lengths to find and remove them. I have found few significant errors in the […]

Criteria for good software

What is the difference between good software and bad software? It is reasonably easy to recognise the extremes when we encounter them, but there is a set of criteria that can be used to explain the differences. These criteria are also useful when building or modifying software, as they can be used to help make […]


Good software must be maintainable. It is very rarely the case that a piece of software is developed once and then never nedds to be changed again during its lifetime. This is especially true of user-developed software such as spreadsheets, whose big advantage is that they are easily modified. Even if the requirements do not […]