"Is software reliability important? Ask your grandma," says operating systems guru Dr Andrew Tanenbaum.

When consumers go to buy an electrical appliance such as a TV or stereo they expect to bring it home, plug it in and see it work. And it is exactly what happens -- for years on end. But not so with computers, even though it should, says Tanenbaum, author and Professor of Computer Science at Vrije Universiteit in Holland.

Tanenbaum used last week's linux.conf.au to introduce his new metric: LFs -- Lifetime Failures, which he says is the number of times software, particularly the operating system, has crashed in a user's lifetime.

He said there was no reason why PC consumers should expect mediocrity from their operating systems. "A TV doesn't have a rest button," he said.

But how to do this?

"I think it is time we rethink operating systems," he said. "We have to rethink where we are going in 2007. We have basically infinite hardware and the only reason it's slow is because the performance is so bad."

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."

He referred to RAID arrays and ECC memory as hardware devices which, when they encounter errors, can correct them on the fly.

"Correcting bad software on the fly surely should be easier than correcting bad hardware. So I think we need to go in the direction of self healing software," he said.