Bell Telephone Laboratories relay computing devices - Revision history

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The '''Bell Telephone Laboratories relay computing devices''' were a series of [[digital]] [[computing device]]s, using [[relay]]s for [[logic]] and [[memory]], the early ones architected by [[George Stibitz]] at [[Bell Laboratories]] in the late 1930's and early 1940's, and built (with the design assistance of Samuel B. Williams, C. E. Boman and E. G. Andrews) and used on a variety of computing problems. They grew in capabilities, complexity, and size from the earliest one, which seems to have been a ''sui generis'' invention by Stibitz, through the rest of the series.

They were [[binary]] internally, suitable for the relay technology of which they were built, but could do [[input/output|I/O]] in decimal, for the convenience of their users.

They included:

'''Model I''' - Also called the 'Complex Computer', it was a calculator capable of performing arithmetical operations on [[complex number]]s; these are much used in [[analog]] [[electrical engineering]], a major field for engineers at Bell Labs, in which addition is relatively easy to do by hand, but multiplication is not. To ease the conversion of large numbers it used [[binary-coded decimal]] internally, in 'plus-three' form - i.e. 0 was represented as '0011', and 9 as '1100'. It handled [[operand]]s of up to 8 decimal digits, with 2 extra digits to minimize round-off errors.

It using 450 relays, and was completed in October 1939, and placed in use on 8th January, 1940. It was remotely demonstrated at a meeting of the American Mathematical Society at Dartmouth College in Hanover, New Hampshire in September, 1940; the machine remained in New York, but was connected to an I/O station at the meeting over telephone lines. (A predecessor of the 'Mother of all Demos' of the [[Augmentation Research Center]]!)

'''Model II''' - Aso called the 'Relay Interpolator', it was a specialized machine built to solve fire control problems. It (and all following Models) used [[bi-quinary]] internal representation, adopted for its error-checking capabilities. It was [[program]]mable, with the program stored on a [[paper tape]] loop; it also used paper tape for I/O. It was slightly smaller; 440 relays.

'''Model III''' - Also used for fire control problems, it was a more general-purpose machine; it included a number of novel features, such as the use of some [[register]]s as [[index register]]s. It was considerably larger; 1,400 relays. It (and all following Models) operated in un-attended mode.

'''Model IV''' - Very similar to the Model III, it could also perform trigonometric functions. It was about the same size; 1,425 relays.

'''Model V''' - Two built (one delivered in 1946; one in 1947); architecturally, it was a generation past the Models I-IV. It had up to 6 "computers" (what today would be called [[arithmetic logic unit|ALUs]]); as soon as one was idle, it automatically started the next "problem". It used one paper tape reader for input data, up to five for [[instruction]]s (which allowed considerable easy use of [[subroutine]]s), and six for table data. It had support for [[floating point]] (the first to do so), using exponential notation. It was considerably larger again; 9,000 relays.

'''Model VI''' - Similar to the Model V, but somewhat simpler; it had another novelty: each of its three paper tape readers could hold either data or instructions. It was considerably smaller; 4,600 relays; its designers had apparently decided that the increased powers of the Model V were not worth the extra expense, or attendant complexity. (Perhaps the very first case of [[Second System Syndrome]]?)

==See also==

* [[Notable early computing devices]]

==Further reading==

* George Stibitz, ''Computer'', in Brian Randell (editor), ''The Origins of Digital Computers: Selected Papers'', Springer-Verlag, Berlin, Heidelberg, New York, 1973, 1982 (3rd edition)
* George Stibitz, ''Early Computers'', in Nicholas Metropolis, Jack Howlett, Gian-Carlo Rota (editors), [https://www.sciencedirect.com/book/9780124916500/a-history-of-computing-in-the-twentieth-century ''A History of Computing in the Twentieth Century''], Academic Press, New York, 1980
* E. G. Andrews, [https://archive.org/details/bstj42-2-341/mode/1up?view=theater ''Telephone Switching and the Early Bell Laboratories Computers''], [[Bell System Technical Journal|BSTJ]] Vol. 42(2), 341, 1963 - the author was present at Bell Labs from the 1920's on
* O. Cesareo, ''The Relay Interpolator'', in Brian Randell (editor), ''The Origins of Digital Computers: Selected Papers''
* Paul E. Ceruzzi, [https://ed-thelen.org/comp-hist/CBC-Ch-06.pdf ''Chapter Six: Relay Calculators''], in William Aspray (editor), [https://ed-thelen.org/comp-hist/CBC.html ''Computing Before Computers''], Iowa State University Press, Ames, 1990

[[Category: Early Computing Devices]]

@@ Line 32: / Line 32: @@
 * E. G. Andrews, [https://archive.org/details/bstj42-2-341/mode/1up?view=theater ''Telephone Switching and the Early Bell Laboratories Computers''], [[Bell System Technical Journal|BSTJ]] Vol. 42(2), 341, 1963 - the author was present at Bell Labs from the 1920's on
-* [https://ed-thelen.org/comp-hist/Reckoners-ch-4.html ''Chapter 4: Number, Please - Computers at Bell Labs''], in Paul E. Ceruzzi, ''Reckoners: The Prehistory of The Digital Computer, From Relays to the Stored Program Concept, 1935-1945'', Greenwood, Westport, 1983
+* [https://ed-thelen.org/comp-hist/Reckoners-ch-4.html ''Chapter 4: Number, Please - Computers at Bell Labs''], in Paul E. Ceruzzi, [https://www.ed-thelen.org/comp-hist/Reckoners.html ''Reckoners: The Prehistory of The Digital Computer, From Relays to the Stored Program Concept, 1935-1945''], Greenwood, Westport, 1983
 * Paul E. Ceruzzi, [https://ed-thelen.org/comp-hist/CBC-Ch-06.pdf ''Chapter Six: Relay Calculators''], in William Aspray (editor), ''Computing Before Computers'', Iowa State University Press, Ames, 1990
 [[Category: Early Computing Devices]]

@@ Line 1: / Line 1: @@
-The '''Bell Telephone Laboratories relay computing devices''' were a series of [[digital]] [[computing device]]s, using [[relay]]s for [[logic]] and [[memory]], the early ones architected by [[George Stibitz]] at [[Bell Laboratories]] in the late 1930's and early 1940's, and built (with the design assistance of Samuel B. Williams, C. E. Boman and E. G. Andrews) and used on a variety of computing problems. They grew in capabilities, complexity, and size from the earliest one, which seems to have been a ''sui generis'' invention by Stibitz, through the rest of the series.
+The '''Bell Telephone Laboratories relay computing devices''' were a series of [[digital]] [[computing device]]s, using [[relay]]s for both [[logic]] and [[memory]], all architected by [[George Stibitz]] at [[Bell Laboratories]] in the late 1930's and early 1940's, and built with the design assistance of Samuel B. Williams, C. E. Boman and E. G. Andrews, and used on a variety of computing problems. They grew in capabilities, complexity, and size from the earliest one (which seems to have been a ''sui generis'' invention by Stibitz), through the rest of the series.
-They were [[binary]] internally, suitable for the relay technology of which they were built, but could do [[input/output|I/O]] in decimal, for the convenience of their users.
+They were [[binary]] internally, suitable for the relay technology of which they were built, but could do [[input/output|I/O]] in decimal, for the convenience of their users. They included:
-They included:
+'''Model I''' - Also called the 'Complex Computer', it was a calculator capable of performing arithmetical operations on [[complex number]]s; these are much used in [[analog]] [[electrical engineering]] (a major field for engineers at Bell Labs), in which addition is relatively easy to do by hand, but multiplication is not. To ease the conversion of large numbers it used [[binary-coded decimal]] internally, in 'plus-three' form - i.e. 0 was represented as '0011', and 9 as '1100'. It handled [[operand]]s of up to 8 decimal digits, with 2 extra digits internally to minimize round-off errors.
-'''Model I''' - Also called the 'Complex Computer', it was a calculator capable of performing arithmetical operations on [[complex number]]s; these are much used in [[analog]] [[electrical engineering]], a major field for engineers at Bell Labs, in which addition is relatively easy to do by hand, but multiplication is not. To ease the conversion of large numbers it used [[binary-coded decimal]] internally, in 'plus-three' form - i.e. 0 was represented as '0011', and 9 as '1100'. It handled [[operand]]s of up to 8 decimal digits, with 2 extra digits to minimize round-off errors.
+It used 450 relays, and was completed in October 1939, and placed in use on 8th January, 1940. It was remotely demonstrated at a meeting of the American Mathematical Society at Dartmouth College in Hanover, New Hampshire on 11th September, 1940; the machine remained in New York, but was connected to an I/O station at the meeting over telephone lines. (A predecessor of the 'Mother of all Demos' of the [[Augmentation Research Center]]!)
-It using 450 relays, and was completed in October 1939, and placed in use on 8th January, 1940. It was remotely demonstrated at a meeting of the American Mathematical Society at Dartmouth College in Hanover, New Hampshire in September, 1940; the machine remained in New York, but was connected to an I/O station at the meeting over telephone lines. (A predecessor of the 'Mother of all Demos' of the [[Augmentation Research Center]]!)
+'''Model II''' - Also called the 'Relay Interpolator', it was a specialized machine built to solve fire control problems; it was completed in July, 1943. It (and all following Models) used [[bi-quinary]] internal representation, adopted for its error-checking capabilities. It was [[program]]mable, with the program stored on a [[paper tape]] loop; it also used paper tape for I/O. It was slightly smaller than the Model I; 440 relays.
-'''Model II''' - Aso called the 'Relay Interpolator', it was a specialized machine built to solve fire control problems. It (and all following Models) used [[bi-quinary]] internal representation, adopted for its error-checking capabilities. It was [[program]]mable, with the program stored on a [[paper tape]] loop; it also used paper tape for I/O. It was slightly smaller; 440 relays.
+'''Model III''' - Also called the 'Ballistic Computer', it also was used for fire control problems; it was completed in June, 1944. It was a more general-purpose machine than the Mark III; it included a number of novel features, such as the use of some [[register]]s as [[index register]]s. It was considerably larger than the Model II; 1,400 relays. It (and all following Models) could operate in un-attended mode.
-'''Model III''' - Also used for fire control problems, it was a more general-purpose machine; it included a number of novel features, such as the use of some [[register]]s as [[index register]]s. It was considerably larger; 1,400 relays. It (and all following Models) operated in un-attended mode.
+'''Model IV''' - Very similar to the Model III, it could also perform trigonometric functions. Completed in March, 1945, it was about the same size; 1,425 relays.
-'''Model IV''' - Very similar to the Model III, it could also perform trigonometric functions. It was about the same size; 1,425 relays.
+'''Model V''' - Two built (one delivered in December, 1946; one in August, 1947); architecturally, it was a generation past the Models I-IV. It was designed to have up to 6 "computers" (what today would be called [[arithmetic logic unit|ALUs]]); as soon as one was idle, it automatically started the next "problem". It only had 2, as built; it used one paper tape reader for input data, up to five for [[instruction]]s (which allowed considerable easy use of [[subroutine]]s), and six for table data. It had support for [[floating point]] (the first Bell relay machine to do so), using exponential notation. It was considerably larger again; 9,000 relays.
-'''Model V''' - Two built (one delivered in 1946; one in 1947); architecturally, it was a generation past the Models I-IV. It had up to 6 "computers" (what today would be called [[arithmetic logic unit|ALUs]]); as soon as one was idle, it automatically started the next "problem". It used one paper tape reader for input data, up to five for [[instruction]]s (which allowed considerable easy use of [[subroutine]]s), and six for table data. It had support for [[floating point]] (the first to do so), using exponential notation. It was considerably larger again; 9,000 relays.
+'''Model VI''' - Similar to the Model V, but somewhat simpler; it had another novelty: each of its three paper tape readers could hold either data or instructions. It was considerably smaller; 4,600 relays; its designers had apparently decided that the increased powers of the Model V were not worth the extra expense, or attendant complexity. (Perhaps the very first case of [[Second System Syndrome]]?)
-'''Model VI''' - Similar to the Model V, but somewhat simpler; it had another novelty: each of its three paper tape readers could hold either data or instructions. It was considerably smaller; 4,600 relays; its designers had apparently decided that the increased powers of the Model V were not worth the extra expense, or attendant complexity. (Perhaps the very first case of [[Second System Syndrome]]?)
+The Models II-V were produced for the armed forces (all remained in use until around 1960); only the I and VI were used by Bell. The bi-quinary machines were very reliable (in the sense of never producing erroneous results), even though they used relays, which were inherently un-reliable; the continuous self-checking possible with the bi-quinary representation was responsible.
 ==See also==
@@ Line 29: / Line 29: @@
 * E. G. Andrews, [https://archive.org/details/bstj42-2-341/mode/1up?view=theater ''Telephone Switching and the Early Bell Laboratories Computers''], [[Bell System Technical Journal|BSTJ]] Vol. 42(2), 341, 1963 - the author was present at Bell Labs from the 1920's on
 * O. Cesareo, ''The Relay Interpolator'', in Brian Randell (editor), ''The Origins of Digital Computers: Selected Papers''
-* Paul E. Ceruzzi, [https://ed-thelen.org/comp-hist/CBC-Ch-06.pdf ''Chapter Six: Relay Calculators''], in William Aspray (editor), [https://ed-thelen.org/comp-hist/CBC.html ''Computing Before Computers''], Iowa State University Press, Ames, 1990
+* [https://ed-thelen.org/comp-hist/Reckoners-ch-4.html ''Chapter 4: Number, Please - Computers at Bell Labs''], in Paul E. Ceruzzi, ''Reckoners: The Prehistory of The Digital Computer, From Relays to the Stored Program Concept, 1935-1945'', Greenwood, Westport, 1983
 [[Category: Early Computing Devices]]