Winn L. Rosch Hardware Bible, Sixth Edition

Layouts

On a full-size keyboard, the spacing between the keycaps for individual character keys is 0.75 inch (19 millimeters), center to center. The keycaps themselves are about 0.5 inch (12.5 millimeters) across at the top, dished to help you place your fingers. The shape of this curve is somewhat arbitrary. Most American designs put a concave cylindrical curve (it's curved only around the longitudinal axis) at the top of the keys; some European designs use a concave spherical curve.

QWERTY

The one unvarying aspect of keyboards also seems the most odd—the nonalphabetical arrangement of the alphabet keys. Anyone new to typing will be amazed and perplexed at the seemingly nonsensical arrangement of letters on the keys of the typical computer keyboard. ...