Slab (unit)

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Not to be confused with slab allocation.

A slab or syllable is the primary unit of memory in the NCR 315 computer architecture from NCR Corporation. Having 12 data bits and a parity bit, its size falls between a byte and a typical word (hence the name, 'syllable'). A slab may contain three digits (with at sign, comma, space, ampersand, point, and minus treated as digits) or two alphabetic characters. A slab may contain a decimal value from -99 to +999.

A numeric value contains up to eight slabs. If the value is negative then the minus sign is the leftmost digit of this row. There are commands to transform digits into alphanumeric characters or inverse. All these commands use the accumulator which has a maximum length of eight slabs. To accelerate the processing the accumulator works with an effective length.

The NCR 315 was the follow-on to the NCR 304.


  • Bardin, H (1963). "NCR 315 Seminar", Computer Usage Communique, Vol.2, No. 3., 1963. [1]