Small Memory for Large Numbers

Measured against the mammoth computers for which they were designed, the tiny bits of ceramic hardly seem significant. But the memory units developed by the Sandia Corp. of Albuquerque may succeed in teaching man's rapidly evolving mechanical brains how to talk in another mathematical language.

At present, even the most versatile digital computers have memories that can cope with only a limited vocabulary. Switches and relays may be open or closed, holes may be present or absent from a punched card, bits of magnetism may or may not be spotted on a tape. But whatever the computer memory is composed of, it uses, in effect, only two words: yes and no. As a result, the machine can count only in what mathematicians call binary notation. Familiar decimal numbers, which are composed of the ten digits, 0 through 9, must be translated into binary notation before they are fed into a computer.

Numbers for Words. Binary notation uses only two digits. 1 (yes) and 0 (no). Each digit tells whether a given power of 2 is part of the number with which the computer is dealing (see diagram). Numerical information, such as figures from a payroll, can be easily translated into binary notation for storage in a computer's memory. Written English requires another step. Each letter of the alphabet, for example, might be assigned a decimal number (A=l, B = 2, C = 3, etc.). Whole words would be translated into decimal numbers, and the decimal numbers, in turn, translated into binary for the computer.

Although binary numbers are remarkably handy, they are also noticeably bulky. Complex computers now need hundreds of thousands of yes-no units before they can be said to have a satisfactory memory. Sandia's memory units should allow considerable shrinkage.

Magnetic Ceramic. The ceramic is magnetized by pulses of electricity, but instead of recording simply the presence or absence of magnetism, the Sandia material responds differently to different amounts of electricity. Two pulses magnetize it twice as strongly as one pulse; three pulses do three times the job. The ceramic is so sensitive that any digit up to nine can be recorded on a single piece.

Sandia's men are not suggesting that all computers should now be taught to talk and think in decimal numbers, but they are convinced that for certain kinds of machine memory a decimal storage system could save much space and cost. Improved ceramic may soon be able to store more than 9 digits, but even the present wafers have obvious advantages. Stored away in binary notation, the number 99 takes seven memory units (1100011), whatever the memory , is made of--holes in a card or magnetic cores. In Sandia's decimal memory system, it would take only two tiny chips of ceramic.

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