Designers' tools: The big roundup of small calculators: Hand-held calculators are getting smaller and smarter; they make the slide rule a museum piece

Where engineering, science, and business are concerned, the portable personal calculator is rapidly moving from a novelty to a necessity. The technologists have found more than just a fancy replacement for their trusted slide rules. Running circles around any slipstick, the latest scientific portables feature memory, programming capability, and readouts in scientific notation, while turning out answers in fractions of a second. Accountants and bankers can relate to another special breed of electronic brain with built-in subroutines for bond, mortgage, and interest rate problems — keeping them ahead of the paperwork. There's even a calculator intended just to handle conversion problems between metric and U.S. measurement.