Two generations ago a standard uniform identified engineers: white shirt, narrow tie, pocket protector and slide rule. The shirt and tie evolved into a T-shirt sporting some software advertisement. The pocket protector has been replaced by a cell phone holster. And the slide rule has become an electronic calculator.

Take another look at that slide rule. Pull it out of the drawer you stashed it in 30 years ago or make one of your own. You'll see why it was once so valuable.