To this he added a disclaimer: "Performance for the most part isn't an issue: bad code is."

To illustrate the complexity of operating system software, he pointed out the rise in the amount of code for Microsoft's Windows software over the past decade. Windows NT 3.5 started out with 6 million lines of code (LoC) in 1993. NT 4 in 1996 had 16 million LoC, Windows 2000 had 29 million LoC and XP had 50 million LoC.

With an average bug rate of anywhere from 10-75 per 1000 LoC, the chances for errors and failures rises sharply, he said.

Tanenbaum was critical of software design today, saying there were far too many features, many of which were unnecessary in applications. He said as software gets more bloated, it becomes less reliable, more buggy, and slow.

"I think that is a bad direction to go into."