Okay, drop what you’re doing and look down at your keyboard right now. If you’re using a PC-style keyboard, go over to the block of six keys with “home,” “end,” and “page up / page down”. Look at the set of three keys above.

If you’ve got a standard keyboard, you’ll see these: “Print Screen / SysRq”, “Scroll Lock”, and “Pause / Break”. Have you ever used them in your entire life? Do you even know what they mean?

Fortunately, The Straight Dope web site has put together a quite hilarious primer on why these keys exist and what they’re originally used for. As it turns out, they’re a relic of early computation — a sort of left-over byproduct of Darwinian evolution, a ghost echo of weird things that people used to do on old-school DOS systems. For example:

The main intent of the Scroll Lock key was to allow scrolling of screen text up, down and presumably sideways using the arrow keys in the days before large displays and graphical scroll bars. You can see where this might have been handy in the DOS era, when screen output typically was limited to 80 characters wide by 25 rows deep. For some types of programs, spreadsheets being the obvious example, it’s still handy now. In Microsoft Excel, Scroll Lock allows you to scroll a spreadsheet with the arrow keys without moving the active cell pointer from the currently highlighted cell. In Quattro Pro, another spreadsheet program, Scroll Lock works in a similar manner, although in contrast to Excel it’s not possible to scroll the active cell pointer completely off the screen …

The ancient DOS adventure game “Rogue” (one of my all-time favorites) used Scroll Lock to scroll your character’s movement through the ASCII dungeons on the display.

(Thanks to Slashdot for this one!)