The NCR 315 Data Processing System, released in January 1962 by NCR, is a second-generation

computer A computer is a machine that can be programmed to carry out sequences of arithmetic or logical operations ( computation) automatically. Modern digital electronic computers can perform generic sets of operations known as programs. These prog ...

. All

printed circuit board A printed circuit board (PCB; also printed wiring board or PWB) is a medium used in electrical and electronic engineering to connect electronic components to one another in a controlled manner. It takes the form of a laminated sandwich str ...

s use

resistor–transistor logic Resistor–transistor logic (RTL) (sometimes also transistor–resistor logic (TRL)) is a class of digital circuits built using resistors as the input network and bipolar junction transistors (BJTs) as switching devices. RTL is the earliest class o ...

(RTL) to create the various logic elements. It uses 12-bit ''slab'' memory structure using

magnetic-core memory Magnetic-core memory was the predominant form of random-access computer memory for 20 years between about 1955 and 1975. Such memory is often just called core memory, or, informally, core. Core memory uses toroids (rings) of a hard magnet ...

. The instructions can use a memory slab as either two 6-bit alphanumeric characters or as three

4-bit In computer architecture, 4-bit integers, or other data units are those that are 4 bits wide. Also, 4-bit central processing unit (CPU) and arithmetic logic unit (ALU) architectures are those that are based on registers, or data buses of that si ...

BCD digits. Basic memory is 5000 "slabs" (10,000 characters or 15,000 decimal digits) of handmade core memory, which is expandable to a maximum of 40,000 slabs (80,000 characters or 120,000 decimal digits) in four refrigerator-size cabinets. The main processor includes three cabinets and a console section that houses the power supply, keyboard, output writer (an IBM electric typewriter), and a

panel Panel may refer to: Arts and media Visual arts *Panel (comics), a single image in a comic book, comic strip or cartoon; also, a comic strip containing one such image *Panel painting, in art, either one element of a multi-element piece of art, ...

with lights that indicate the current status of the program counter, registers, arithmetic accumulator, and system errors. Input/Output is by direct parallel connections to each type of peripheral through a two-cable bundle with 1-inch-thick cables. Some devices like

magnetic tape Magnetic tape is a medium for magnetic storage made of a thin, magnetizable coating on a long, narrow strip of plastic film. It was developed in Germany in 1928, based on the earlier magnetic wire recording from Denmark. Devices that use magnet ...

and the

CRAM Cram may refer to: * Cram (surname), a surname, and list of notable persons having the surname * Cram.com, a website for creating and sharing flashcards * Cram (Australian game show), a television show * ''Cram'' (game show), a TV game show th ...

are daisy-chained to allow multiple drives to be connected. The central processor (315 Data Processor) weighed about . Later models in this series include the 315-100 and the 315-RMC (Rod Memory Computer).

Memory organization

The addressable unit of memory on the NCR 315 series is a "slab", short for "syllable", consisting of 12 data bits and a

parity bit A parity bit, or check bit, is a bit added to a string of binary code. Parity bits are a simple form of error detecting code. Parity bits are generally applied to the smallest units of a communication protocol, typically 8-bit octets (bytes), ...

. Its size falls between a

byte The byte is a unit of digital information that most commonly consists of eight bits. Historically, the byte was the number of bits used to encode a single character of text in a computer and for this reason it is the smallest addressable uni ...

and a typical

word A word is a basic element of language that carries an objective or practical meaning, can be used on its own, and is uninterruptible. Despite the fact that language speakers often have an intuitive grasp of what a word is, there is no conse ...

(hence the name, '

syllable A syllable is a unit of organization for a sequence of speech sounds typically made up of a syllable nucleus (most often a vowel) with optional initial and final margins (typically, consonants). Syllables are often considered the phonological ...

'). A slab may contain three digits (with at sign,

comma The comma is a punctuation mark that appears in several variants in different languages. It has the same shape as an apostrophe or single closing quotation mark () in many typefaces, but it differs from them in being placed on the baseline ...

space Space is the boundless three-dimensional extent in which objects and events have relative position and direction. In classical physics, physical space is often conceived in three linear dimensions, although modern physicists usually consi ...

ampersand The ampersand, also known as the and sign, is the logogram , representing the conjunction "and". It originated as a ligature of the letters ''et''—Latin for "and". Etymology Traditionally in English, when spelling aloud, any letter tha ...

, point, and

minus The plus and minus signs, and , are mathematical symbols used to represent the notions of positive and negative, respectively. In addition, represents the operation of addition, which results in a sum, while represents subtraction, resul ...

treated as digits) or two alphabetic characters of six bits each. A slab may contain a

decimal The decimal numeral system (also called the base-ten positional numeral system and denary or decanary) is the standard system for denoting integer and non-integer numbers. It is the extension to non-integer numbers of the Hindu–Arabic numeral ...

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 instructions to transform digits to or from alphanumeric characters. These commands use the accumulator, which has a maximum length of eight slabs. To accelerate the processing the accumulator works with an effective length.

NCR 315-100

The NCR 315-100 is the second version of the original 315. It too has a 6-microsecond clock cycle, and from 10,000 to 40,000 slabs of memory. The 315-100 series console I/O incorporates a Teletype printer and keyboard in place of the original 315's IBM typewriter. The primary difference between the older NCR 315 and the 315-100 was the inclusion of the Automatic Recovery Option (ARO). One of the problems with early generation of computers was that when a memory or program error occurred, the system would simply turn on a red light and halt. The normal recovery process was to copy all register and counter setting from the console light panel, and to restart the program that was running at the time of the error, usually from the very beginning of the program. The upgrade to the 315 required the removal of approximate 1800 wire-wrapped connection on the backplane, and the installation of approximately 2400 new point-to-point wired connection.

NCR 315-RMC

The NCR 315-RMC, released in July 1965, was the first commercially available computer to employ thin-film memory. This reduced the clock cycle time to 800 nanoseconds. It also included

floating-point In computing, floating-point arithmetic (FP) is arithmetic that represents real numbers approximately, using an integer with a fixed precision, called the significand, scaled by an integer exponent of a fixed base. For example, 12.345 can ...

logic to allow scientific calculations, while retaining the same instruction set as previous NCR 315 and NCR 315-100. The thin film is wrapped around "rods" to allow faster reading and writing of memory. The follow-on to the 315-RMC was the NCR Century series.

Available languages

* NCR Assembler Language * National Electronic Autocoding Technique (NEAT) — similar to

Autocoder Autocoder is any of a group of assemblers for a number of IBM computers of the 1950s and 1960s. The first Autocoders appear to have been the earliest assemblers to provide a macro facility. Terminology Both ''autocoder'', and the unrelated ' ...

COBOL COBOL (; an acronym for "common business-oriented language") is a compiled English-like computer programming language designed for business use. It is an imperative, procedural and, since 2002, object-oriented language. COBOL is primarily u ...

* BEST— a high-level preproocesor for NEAT

Available peripherals

* NCR-321 Communications Controller *

NCR-340 The NCR-340 was NCR's first line "High Speed" 300-line-per-minute computer printer. It used a drum made up of 120 (later 132) hardened steel discs with the upper-case alphabet, the numbers 0-9 and a few special symbols. The discs were keyed on an ...

600-LPM line printer * Magnetic tapes ** NCR-332 Magnetic tape drive (512 bpi) ** NCR-333 Control Data

CDC The Centers for Disease Control and Prevention (CDC) is the national public health agency of the United States. It is a United States federal agency, under the Department of Health and Human Services, and is headquartered in Atlanta, Georg ...

tape drive (512 bpi) ** NCR-334 Magnetic Tape Drive (200/512 bpi) * NCR-353 Magnetic Card Random Access Memory (

) * Card and

paper tape Five- and eight-hole punched paper tape Paper tape reader on the Harwell computer with a small piece of five-hole tape connected in a circle – creating a physical program loop Punched tape or perforated paper tape is a form of data storage ...

equipment ** NCR-361 Paper Tape Reader ** NCR-371 Paper Tape Punch ** NCR-376 IBM Card Reader/Punch ** NCR-380 2000 CPS High speed card reader ** NCR-472 Card Reader, Paper Tape Reader/Punch * NCR-???

Drum memory Drum memory was a magnetic data storage device invented by Gustav Tauschek in 1932 in Austria. Drums were widely used in the 1950s and into the 1960s as computer memory. For many early computers, drum memory formed the main working memory of ...

* NCR-402 MICR Check Reader/Sorter * NCR-420 Optical Character Reader ( OCR) * NCR-407 High Speed MICR Check Reader/Sorter

External links

Rod Memory description
*

References

{{DEFAULTSORT:Ncr 315 Mainframe computers Transistorized computers NCR Corporation products