History of Computers and Computing, Birth of the modern computer, Electronic computer, Manchester Small Scale Experimental Machine SSEM computer of Frederic Williams and Tom Kilburn The world's first stored-program electronic digital computer, the English Small Scale Experimental Machine (SSEM, nicknamed the Baby) successfully executed its first program on 21st June 1948. That program was written by Tom Kilburn, who actually built the machine, designed by his mentor—Frederic (Freddie) Williams. Frederic Calland Williams (1911-1977) gained a BSc (1932) and MSc (1933) degrees in Engineering at University of Manchester, and a Doctor degree at Oxford University. Then he took up the post of Assistant Lecturer in his old department at Manchester. During the next few years he made many outstanding contributions to research in electronics, publishing some 20 papers. Two of these were with Prof. Blackett on an automatic curve follower for the Hartree Differential Analyser, a famous mechanical calculator constructed at the University of Manchester in the early thirties.

During the WWII Williams made outstanding contributions to the electronics of radar and other military equipment, producing, amongst other things, the first operational amplifier. In June 1946 he started investigation into the storage of both analog and digital information on a Cathode Ray Tube. Storage of analog information could help solve the problem of static objects cluttering the dynamic picture on a radar screen. Storage of digital information could solve the problem holding up the development of computers worldwide, i.e. lack of a storage mechanism that would work at electronic speeds. Williams demonstrated the successful operation of a single bit memory using the anticipation pulse method in October, and provisionally patented this system in December 1946. The bit was stored in the form of a charge on the CRT screen's phosphor, which could be controlled by the electron beam to write a 0 or a 1. Although the phosphor was an electrical insulator, the charge would leak away in the order of a second. Williams arranged to read the charge and then rewrite it continuously at electronic speeds so that information could be kept permanently; this process was called regeneration and the principle is still used today to replenish charge on modern integrated circuit RAMs.

In December 1946 Freddie Williams moved to the University of Manchester to take up a chair in Electro-Technics. He continued to work on the system, and some of his group members followed him, between them was Tom Kilburn (1921-2001), a mathematician, who had worked in his group since 1942. In the end of 1947, 2048 bits were being stored on a standard single 6 inch diameter CRT, and an internal report had been written by Tom Kilburn introducing the "dot-dash" and the "defocus-focus" methods of operation of the CRT and the design of a hypothetical computer. This report aroused considerable interest and was widely circulated in the UK and USA. The CRT storage system became known as the Williams Tube. Though the store could remember 2048 bits, an individual bit could only be reset by hand, and it was necessary to test its capability of setting and reading any required bit at electronic speeds and remembering its value indefinitely between settings. So the next step was to build a small computer around a CRT memory, to subject it to the "most effective and searching tests possible".

Williams and Kilburn knew all for electronics, but a little for computers, so they headed for consultations to their colleagues, the famous mathematician Alan Turing and Max Newman, the creator of Colossus . Using the advises of the computer geniuses, Williams designed the computer, which was built mainly by Kilburn and his colleagues. This computer was built in half an year—the Small Scale Experimental Machine (SSEM) included the stored-program concept, so that the Random Access Memory was used not only to hold numbers involved in calculations, but to hold the program instructions. This meant that instructions could be read successively at electronic speed, and that running a different program only involved resetting part of the memory using a simple keyboard rather than reconfiguring the electronic circuitry (this could take days on ENIAC). SSEM in 1948 Work on building the SSEM took place in the first half of 1948, and was mainly carried out by Tom Kilburn with the assistance of Geoff Tootill. The arithmetical device was built by vacuum tubes, while the memory, registers and the display was based on Williams Tubes. The input was a keyboard.

The Baby machine had the following properties: • 32-bit word length manchester small scale experimental machine : definition of manchester small scale experimental machine and synonyms of manchester small scale experimental machine (English) Replica of the Small-Scale Experimental Machine (SSEM) at the Museum of Science and Industry in Castlefield , Manchester The Manchester Small-Scale Experimental Machine (SSEM), nicknamed Baby, was the world's first stored-program computer . It was built at the Victoria University of Manchester by Frederic C. Williams , Tom Kilburn and Geoff Tootill, and ran its first program on 21 June 1948. [1] The machine was not intended to be a practical computer but was instead designed as a testbed for the Williams tube , an early form of computer memory. Although considered "small and primitive" by the standards of its time, it was the first working machine to contain all of the elements essential to a modern electronic computer. [2] As soon as the SSEM had demonstrated the feasibility of its design, a project was initiated at the university to develop it into a more usable computer, the Manchester Mark 1 .

The Mark 1 in turn quickly became the prototype for the Ferranti Mark 1 , the world's first commercially available general-purpose computer. [3] The SSEM had a 32- bit word length and a memory of 32 words. As it was designed to be the simplest possible stored-program computer, the only arithmetic operations implemented in hardware were subtraction and negation ; other arithmetic operations were implemented in software. The first of three programs written for the machine found the highest proper divisor of 218 (262,144), a calculation that was known would take a long time to run—and so prove the computer's reliability—by testing every integer from 218 − 1 downwards, as division was implemented by repeated subtraction of the divisor. The program consisted of 17 instructions and ran for 52 minutes before reaching the correct answer of 131,072, after the SSEM had performed 3.5 million operations (for an effective CPU speed of 1.1 kIPS ). Contents Artistic representation of a Turing machine The first design for a program-controlled computer was Charles Babbage 's Analytical Engine in the 1830s.

A century later, in 1936, mathematician Alan Turing published his description of what became known as a Turing machine , a theoretical concept intended to explore the limits of mechanical computation. Turing was not imagining a physical machine, but a person he called a "computer", who acted according to the instructions provided by a tape on which symbols could be read and written sequentially as the tape moved under a tape head. Turing proved that if an algorithm can be written to solve a mathematical problem, then a Turing machine can execute that algorithm. [4] Konrad Zuse 's Z3 was the world's first working programmable , fully automatic computer, with binary digital arithmetic logic, but it lacked the conditional branching of a Turing machine. On 12 May 1941, it was successfully presented to an audience of scientists of the Deutsche Versuchsanstalt für Luftfahrt ("German Laboratory for Aviation") in Berlin . [5] The Z3 stored its program on an external tape, but it was electromechanical rather than electronic.

The Colossus of 1943 was the first electronic computing device, but was not a general-purpose machine.[ citation needed ] The ENIAC (1946) was the first machine that was both electronic and general purpose. It was Turing complete , with conditional branching, and programmable to solve a wide range of problems, but its program was held in the state of switches in patchcords, not in memory, and it could take several days to reprogram. [2] Researchers such as Turing and Konrad Zuse investigated the idea of using the computer's memory to hold the program as well as the data it was working on, [6] but it was mathematician John von Neumann who became widely credited with defining that computer architecture, still used in almost all computers. [7] Design of the von Neumann architecture (1947) The construction of a von Neumann computer depended on the availability of a suitable memory device on which to store the program. During the Second World War researchers working on the problem of removing the clutter from radar signals had developed a form of delay line memory , the first practical application of which was the mercury delay line, [8] developed by J. Presper Eckert .

Radar transmitters send out regular brief pulses of radio energy, the reflections from which are displayed on a CRT screen. As operators are usually interested only in moving targets, it was desirable to filter out any distracting reflections from stationary objects. The filtering was achieved by comparing each received pulse with the previous pulse, and rejecting both if they were identical, leaving a signal containing only the images of any moving objects. To store each received pulse for later comparison it was passed through a transmission line, delaying it by exactly the time between transmitted pulses. [9] Turing joined the National Physical Laboratory (NPL) in October 1945, [10] by which time scientists within the Ministry of Supply had concluded that Britain needed a National Mathematical Laboratory to coordinate machine-aided computation. [11] A Mathematics Division was set up at the NPL, and on 19 February 1946 Alan Turing presented a paper outlining his design for an electronic stored-program computer to be known as the Automatic Computing Engine (ACE). [11] This was one of several projects set up in the years following the Second World War with the aim of constructing a stored-program computer.

At about the same time, EDVAC was under development at the University of Pennsylvania 's Moore School of Electrical Engineering , and the University of Cambridge Mathematical Laboratory was working on EDSAC . [11] [12] The NPL did not have the expertise to build a machine like ACE, so they contacted Tommy Flowers at the General Post Office 's (GPO) Dollis Hill Research Laboratory . Flowers, the designer of Colossus, the world's first programmable electronic computer, was committed elsewhere and was unable to take part in the project, although his team did build some mercury delay lines for ACE. [11] The Telecommunications Research Establishment (TRE) was also approached for assistance, as was Maurice Wilkes at the University of Cambridge Mathematical Laboratory . [11] The government department responsible for the NPL decided that, of all the work being carried out by the TRE on its behalf, ACE was to be given the top priority. [11] NPL's decision led to a visit by the superintendent of the TRE's Physics Division on 22 November 1946, accompanied by Frederic C. Williams and A. M. Uttley, also from the TRE.

[11] Williams led a TRE development group working on CRT stores for radar applications, as an alternative to delay lines. [13] He had already accepted a professorship at the University of Manchester , and most of his circuit technicians were in the process of being transferred to the Department of Atomic Energy. [11] The TRE agreed to second a small number of technicians to work under Williams' direction at the university, and to support another small group working with Uttley at the TRE. [11] Williams tube Main article: Williams tube Although early computers such as CSIRAC made successful use of mercury delay line memory, [14] the technology had several drawbacks; it was heavy, it was expensive, and it did not allow data to be accessed randomly. In addition, because data was stored as a sequence of acoustic waves propagated through a mercury column, the device's temperature had to be very carefully controlled, as the velocity of sound through a medium varies with its temperature. Williams had seen an experiment at Bell Labs demonstrating the effectiveness of cathode ray tubes (CRT) as an alternative to the delay line for removing ground echoes from radar signals.

While working at the TRE, shortly before he joined the University of Manchester in December 1946, he had developed a form of electronic memory known as the Williams tube based on a standard CRT, the first random-access digital storage device. [15] The Manchester Small-Scale Experimental Machine (SSEM) was designed to prove that the Williams tube was a practical storage device, by testing that data held within it could be continuously updated at the speed necessary for use in a computer. [16] For use in a binary digital computer, the tube had to be capable of storing either one of two states at each of its memory locations, corresponding to the binary digits (bits) 0 and 1. It exploited the positive or negative electrostatic charge generated by displaying either a dash or a dot at any position on the CRT screen, a phenomenon known as secondary emission . A dash generated a positive charge, and a dot a negative charge, either of which could be picked up by a detector plate in front of the screen; a negative charge represented 0, and a positive charge 1. The charge dissipated in about 0.2 seconds, but it could be automatically refreshed from the data picked up by the detector.

[17] The Williams tube was initially based on the CV1131, a commercially available 12-inch (300 mm) diameter CRT, but a smaller 6-inch (150 mm) tube, the CV1097, was used in the SSEM. [18] Development and design Architectural schematic showing how the four cathode ray tubes (shown in green) were deployed Following his appointment to the Chair of Electrical Engineering at Manchester University, Williams recruited his TRE colleague Tom Kilburn on secondment. By the autumn of 1947 the pair had increased the storage capacity of the Williams tube from one bit to 2,048, arranged in a 64 by 32-bit array, [19] and demonstrated that it was able to store those bits for four hours. [20] Engineer Geoff Tootill joined the team on loan from TRE in September 1947, and remained on secondment until April 1949. [21] Max Newman had been appointed to the Chair of Pure Mathematics at Manchester University in 1945.

During the Second World War he had worked as a cryptanalyst at Bletchley Park , and had led the team which in 1943 produced the first of the Colossus code-breaking computers. Although Newman played no active role in the development of the SSEM, or any of the subsequent Manchester computers , he was generally supportive and enthusiastic about the project, and arranged for the acquisition of war-surplus supplies for its construction, including GPO metal racks from Bletchley. [22] By June 1948 the SSEM had been built and was working. [19] It was 17 feet (5.2 m) in length, 7 feet 4 inches (2.24 m) tall, and weighed almost 1 long ton (1.0 t). The machine contained 550 valves —300 diodes and 250 pentodes —and had a power consumption of 3500 watts . [23] The arithmetic unit was built using EF50 pentode valves, which had been widely used during wartime.

[20] The SSEM used one Williams tube to provide 32 by 32-bit words of random-access memory (RAM), a second to hold a 32-bit accumulator in which the intermediate results of a calculation could be stored temporarily, and a third to hold the current program instruction along with its address in memory. A fourth CRT, without the storage electronics of the other three, was used as the output device, able to display the bit pattern of any selected storage tube. [24] The output CRT is immediately above the input device, flanked by the monitor and control electronics. Each 32-bit word of RAM could contain either a program instruction or data. In a program instruction, bits 0–12 represented the memory address of the operand to be used, and bits 13–15 specified the operation to be executed, such as storing a number in memory; the remaining 16 bits were unused. [24] The SSEM's single operand architecture meant that the second operand of any operation was implicit: the accumulator or the program counter (instruction address); program instructions specified only the address of the data in memory.

A word in the computer's memory could be read, written, or refreshed, in 360 microseconds. An instruction took four times as long to execute as accessing a word from memory, giving an instruction execution rate of about 700 per second. The main store was refreshed continuously, a process which took 20 milliseconds to complete, as each of the SSEM's 32 words had to be read and then refreshed in sequence. [19] The SSEM represented negative numbers using two's complement , [25] as most computers still do. In that representation, the value of the most significant bit denotes the sign of a number; positive numbers have a zero in that position and negative numbers a one. Thus the range of numbers that could be held in each 32-bit word was −231 to +231 − 1 (decimal: −2,147,483,648 to +2,147,483,647). Programming The SSEM's three bit instruction set allowed a maximum of eight (23) different instructions.

In contrast to the modern convention, the machine's storage was arranged with the least significant digits to the left; thus a one was represented in three bits as "100", rather than the more conventional "001". [25] SSEM's instruction set [26] STP Stop ^ a b As the program counter was incremented at the end of the decoding process, the stored address had to be the target address -1. ^ The function bits were only partially decoded, to save on logic elements. [26] The awkward negative operations were a consequence of the SSEM's lack of hardware to perform any arithmetic operations except subtraction and negation . It was considered unnecessary to build an adder before testing could begin as addition can easily be implemented by subtraction, [24] i.e., x+y can be computed as −(−x−y).

Therefore adding two numbers together, X and Y, required four instructions: [26] LDN X // load negative X into the accumulator SUB Y // subtract Y from the value in the accumulator STO S // store the result at S LDN S // load negative value at S into the accumulator Programs were entered in binary form by stepping through each word of memory in turn, and using a set of 32 switches known as the input device to set the value of each bit of each word to either 0 or 1. The SSEM had no paper-tape reader or punch . [19] First programs The output CRT Three programs were written for the computer. The first, consisting of 17 instructions, was written by Kilburn, and so far as can be ascertained first ran on 21 June 1948. [27] It was designed to find the highest proper factor of 218 (262,144) by trying every integer from 218 − 1 downwards. The divisions were implemented by repeated subtractions of the divisor.

The SSEM took 3.5 million operations and 52 minutes to produce the answer (131,072). The program used eight words of working storage in addition to its 17 words of instructions, giving a program size of 25 words. [28] Geoff Tootill wrote an amended version of the program the following month, and in mid-July Alan Turing—who had been appointed as a reader in the mathematics department at Manchester University in September 1948—submitted the third program, to carry out long division. Turing had by then been appointed to the nominal post of Deputy Director of the Computing Machine Laboratory at the University, [27] although the laboratory did not become a physical reality until 1951. [29] Later developments A plaque in honour of Williams and Kilburn at the University of Manchester Williams and Kilburn reported on the SSEM in a letter to the Journal Nature , published in September 1948. [30] The machine's successful demonstration quickly led to the construction of a more practical computer, the Manchester Mark 1 , work on which began in August 1948.

The first version was operational by April 1949, [29] and it in turn led directly to the development of the Ferranti Mark 1 , the world's first commercially available general-purpose computer. [3] In 1998, a working replica of the SSEM, now on display at the Museum of Science and Industry in Manchester , was built to celebrate the 50th anniversary of the running of its first program. Demonstrations of the machine in operation are held regularly at the museum. [31] In 2008 an original panoramic photograph of the entire machine was discovered at the University of Manchester. The photograph, taken on 15 December 1948 by a research student, Alec Robinson, had been reproduced in The Illustrated London News in June 1949.

[32] [33] See also ^ Panoramic image of SSEM and other audiovisual records (Digital 60, University of Manchester) Bibliography Brown, Louis (1999), A Radar History of World War II: Technical and Military Imperatives, CRC Press, ISBN 978-0-7503-0659-1 Lavington, Simon (1980), Early British Computers: The Story of Vintage Computers and the People who built them (1st ed.), Manchester: Manchester University Press Society, ISBN 0-7190-0803-4 Lavington, Simon (1998), A History of Manchester Computers (2 ed.), Swindon: The British Computer Society, ISBN [[Special:BookSources/0-902505-01-8|0-902505-01-8]] Napper, R. B. E. (2000), "The Manchester Mark 1 Computers" , in Rojas, Raúl; Hashagen, Ulf, The First Computers: History and Architectures, MIT Press, pp.

356–377, ISBN 0-262-68137-4 , Turing, A. M. (1936), "On Computable Numbers, with an Application to the Entscheidungsproblem", Proceedings of the London Mathematical Society, 2 42: 230–265, 1937, DOI : 10.1112/plms/s2-42.1.230 . Further reading Anderson, David (4 June 2004), "Was the Manchester Baby conceived at Bletchley Park?" (PDF), Alan Mathison Turing 2004: A celebration of his life and achievements, British Computer Society , , retrieved 16 November 2008 External links 50th Anniversary of the Manchester Baby computer Computer 50 The University of Manchester Celebrates the Birth of the Modern Computer Update of 26 July 2010: Dr Brian Napper, the author of these pages, sadly passed away in March 2009. The Computer50 pages are now maintained by Toby Howard at the School of Computer Science, The University of Manchester.

For any queries about these pages, please email Toby . The Small-Scale Experimental Machine, known as SSEM, or the "Baby" , was designed and built at The University of Manchester , and made its first successful run of a program on June 21st 1948. It was the first machine that had all the components now classically regarded as characteristic of the basic computer. Most importantly it was the first computer that could store not only data but any (short!) user program in electronic memory and process it at electronic speed. From this Small-Scale Experimental Machine a full-sized machine was designed and built, the Manchester Mark 1 , which by April 1949 was generally available for computation in scientific research in the University. With the integration of a high speed magnetic drum by the Autumn (the ancestor of today's disc) this was the first machine with a fast electronic and magnetic two-level store. It in turn was the basis of the first commercially available computer, the Ferranti Mark 1 , the first machine off the production line being delivered in February 1951.

The highlight of the 1998 Celebrations was the construction of a working replica of the Baby now on display at the Museum of Science and Industry in Manchester (see Galleries > 1830 Warehouse > Baby Computer ). You can see the latest major changes in the pages in the log -- latest entry 30th March 2005 . November 16th 1953 saw the first execution of a program by the "Transistor Computer" -- see the note by its builder, Dick Grimsdale. Manchester Small-Scale Experimental Machine : Map (The Full Wiki) The ENIAC (1946) was the first machine that was both electronic and general purpose. It was Turing complete, with conditional branching, and programmable to solve a wide range of problems. However its program was held in the state of switches in patchcords and not in memory, so it could take several days to reprogram. Researchers such as Turing and Konrad Zuse investigated the idea of using the computer's memory to hold the program as well as the data it was working on, but it was mathematician John von Neumann who became widely credited with defining that computer architecture, still used in almost all computers.

The construction of a von Neumann computer depended on the availability of a suitable memory device on which to store the program. During the Second World War , researchers working on the problem of removing the clutter from radar signals had developed a form of delay line memory , the first practical application of which was the mercury delay line developed by J. Presper Eckert . Radar transmitters send out regular brief pulses of radio energy, the reflections from which are displayed on a CRT screen. As operators are usually interested only in moving targets, it was desirable to filter out any distracting reflections from stationary objects. The filtering was achieved by comparing each received pulse with the previous pulse, and rejecting both if they were identical, leaving a signal containing only the images of any moving objects. To store each received pulse for later comparison it was passed through a transmission line, delaying it by exactly the time between transmitted pulses. Turing joined the National Physical Laboratory (NPL) in October 1945, by which time scientists within the Ministry of Supply had concluded that Britain needed a National Mathematical Laboratory to coordinate machine-aided computation.Lavington (1980), Chapter 5: "ACE, the 'British National Computer'".

A Mathematics Division was set up at the NPL, and on 19 February 1946 Alan Turing presented a paper outlining his design for an electronic stored-program computer to be known as the Automatic Computing Engine (ACE). This was one of several projects set up in the years following the Second World War with the aim of constructing a stored-program computer. At about the same time, EDVAC was under development at the University of Pennsylvania 's Moore School of Electrical Engineering , and the University of Cambridge Mathematical Laboratory was working on EDSAC . The NPL did not have the expertise to build a machine like ACE, so they contacted Tommy Flowers at the General Post Office 's (GPO) Dollis Hill Research Laboratory . Flowers, the designer of Colossus, the world's first programmable electronic computer, was committed elsewhere and was unable to take part in the project, although his team did build some mercury delay lines for ACE. The Telecommunications Research Establishment (TRE) was also approached for assistance, as was Maurice Wilkes at the University of Cambridge Mathematical Laboratory . The government department responsible for the NPL decided that, of all the work being carried out by the TRE on its behalf, ACE was to be given the top priority.

NPL's decision led to a visit by the superintendent of the TRE's Physics Division on 22 November 1946, accompanied by Frederic C. Williams and A. M. Uttley, also from the TRE. Williams led a TRE development group working on CRT stores for radar applications, as an alternative to delay lines. He had already accepted a professorship at the University of Manchester , and most of his circuit technicians were in the process of being transferred to the Department of Atomic Energy. The TRE agreed to second a small number of technicians to work under Williams' direction at the university, and to support another small group working with Uttley at the TRE. Williams tube Although early computers such as CSIRAC made successful use of mercury delay line memory, the technology had several drawbacks; it was heavy, it was expensive, and it did not allow data to be accessed randomly. In addition, because data was stored as a sequence of acoustic waves propagated through a mercury column, the device's temperature had to be very carefully controlled, as the velocity of sound through a medium varies with its temperature.

Williams had seen an experiment at Bell Labs which demonstrated the effectiveness of cathode ray tubes (CRT) as an alternative to the delay line for removing ground echoes from radar signals. While working at the TRE, shortly before he joined the University of Manchester in December 1946, he had developed a form of electronic memory known as the Williams tube based on a standard CRT, the first random-access digital storage device. The Manchester Small-Scale Experimental Machine (SSEM) was designed to prove that the Williams tube was a practical storage device, by testing that data held within it could be continuously updated at the speed necessary for use in a computer. For use in a binary digital computer, the tube had to be capable of storing either one of two states at each of its memory locations, corresponding to the binary digits (bits) 0 and 1. It exploited the positive or negative electrostatic charge generated by displaying either a dash or a dot at any position on the CRT screen, a phenomenon known as secondary emission . A dash generated a positive charge, and a dot a negative charge, either of which could be picked up by a detector plate in front of the screen; a negative charge represented 0, and a positive charge 1.

The charge dissipated in about 0.2 seconds, but it could be automatically refreshed from the data picked up by the detector. The Williams tube was initially based on the CV1131, a commercially available diameter CRT, but a smaller tube, the CV1097, was used in the SSEM. Development and design Following his appointment to the Chair of Electrical Engineering at Manchester University, Williams recruited his TRE colleague Tom Kilburn on secondment. By the autumn of 1947 the pair had increased the storage capacity of the Williams tube from one bit to 2,048, arranged in a 64 by 32-bit array, and demonstrated that it was able to store those bits for four hours. Engineer Geoff Tootill joined the team on loan from TRE in September 1947, and remained on secondment until April 1949. Max Newman had been appointed to the Chair of Pure Mathematics at Manchester University in 1945. During the Second World War he had worked as a cryptanalyst at Bletchley Park , and had led the team which in 1943 produced the first of the Colossus code-breaking computers.

Although Newman played no active role in the development of the SSEM, or any of the subsequent Manchester computers , he was generally supportive and enthusiastic about the project, and arranged for the acquisition of war-surplus supplies for its construction, including GPO metal racks from Bletchley. By June 1948 the SSEM had been built and was working. It was in length, tall, and weighed almost . The machine contained 550 valves —300 diodes and 250 pentodes —and had a power consumption of 3,500 watts . The arithmetic unit was built using EF50 pentode valves, which had been widely used during wartime. The SSEM used one Williams tube to provide 32 by 32-bit words of random-access memory (RAM), a second to hold a 32-bit accumulator in which the intermediate results of a calculation could be stored temporarily, and a third to hold the current program instruction along with its address in memory. A fourth CRT, without the storage electronics of the other three, was used as the output device, able to display the bit pattern of any selected storage tube.

The output CRT is immediately above the input device, flanked by the monitor and control electronics. Each 32-bit word of RAM could contain either a program instruction or data. In a program instruction, bits 0–12 represented the memory address of the operand to be used, and bits 13–15 specified the operation to be executed, such as storing a number in memory; the remaining 16 bits were unused. The SSEM's single operand architecture meant that the implicit second operand of any operation was the accumulator; program instructions specified only the address of the data in memory. A word in the computer's memory could be read, written, or refreshed, in 360 microseconds. An instruction took four times as long to execute as accessing a word from memory, giving an instruction execution rate of about 700 per second. The main store was refreshed continuously, a process which took 20 milliseconds to complete, as each of the SSEM's 32 words had to be read and then refreshed in sequence. The SSEM represented negative numbers using two's complement , as most computers still do.

In that representation, the value of the most significant bit denotes the sign of a number; positive numbers have a zero in that position and negative numbers a one. Thus the range of numbers that could be held in each 32-bit word was −231 to +231 − 1 (decimal: −2,147,483,648 to +2,147,483,647). Programming The SSEM's three bit instruction set allowed a maximum of eight (23) different instructions. In contrast to the modern convention, the machine's storage was arranged with the least significant digits to the left; thus a one was represented in three bits as "100", rather than the more conventional "001". SSEM's instruction set STP Stop The awkward negative operations were a consequence of the SSEM's lack of hardware to perform any arithmetic operations except subtraction and negation . It was considered unnecessary to build an adder before testing could begin since addition can easily be implemented by subtraction, i.e., x+y can be computed as −(−x−y).

Therefore adding two numbers together, X and Y, required four instructions: Programs were entered in binary form by stepping through each word of memory in turn, and using a set of 32 switches known as the input device to set the value of each bit of each word to either 0 or 1. The SSEM had no paper-tape reader or punch . First programs The output CRT Three programs were written for the computer. The first, consisting of 17 instructions, was written by Kilburn, and so far as can be ascertained first ran on 21 June 1948. It was designed to find the highest proper factor of 218 (262,144) by trying every integer from 218 − 1 downwards. The divisions were implemented by repeated subtractions of the divisor. The SSEM took 3.5 million operations and 52 minutes to produce the answer (131,072). The program used eight words of working storage in addition to its 17 words of instructions, giving a program size of 25 words.

Geoff Tootill wrote an amended version of the program the following month, and in mid-July Alan Turing—who had been appointed as a reader in the mathematics department at Manchester University in September 1948—submitted the third program, to carry out long division. Turing had by then been appointed to the nominal post of Deputy Director of the Computing Machine Laboratory at the university, although the laboratory did not become a physical reality until 1951. Later developments A plaque in honour of Williams and Kilburn at the University of Manchester Williams and Kilburn reported on the SSEM in a letter to the Journal Nature , published in September 1948. The machine's successful demonstration quickly led to the construction of a more practical computer, the Manchester Mark 1 , work on which began in August 1948. The first version was operational by April 1949, and it in turn led directly to the development of the Ferranti Mark 1 , the world's first commercially available general-purpose computer.

In 1998, a working replica of the SSEM, now on display at the Museum of Science and Industry in Manchester , was built to celebrate the 50th anniversary of the running of its first program. Demonstrations of the machine in operation are held regularly at the museum. In 2008 an original panoramic photograph of the entire machine was discovered at the University of Manchester. The photograph, taken on 15 December 1948 by a research student, Alec Robinson, had been reproduced in The Illustrated London News in June 1949. References The Williams Tube and the "Manchester Baby," the First Operational Stored-Program Computer Runs its First Program (June 21, 1948) : HistoryofInformation.com Visit HistoryofScience.com » The Williams Tube and the "Manchester Baby," the First Operational Stored-Program Computer Runs its First Program (June 21, 1948) In July 1946 mathematician Max Newman founded the computer laboratory at Manchester University via a grant from the Royal Society. Early on engineers in the department recognized that building an electronic memory would be the most difficult task in building a stored-program computer.

In June 1946, English engineer F.C. (Freddie) Williams had begun research on the storage of both analog and digital information on a cathode ray tube at the Telecommunications Research Establishment . By November 1946 he was able to store a single bit (with the "anticipation" method), based around a standard radar CRT, and filed a provisional patent for the mechanism in December 1946. "In December 1946 Freddie Williams was appointed to a chair at the University of Manchester, and left TRE. However both he and TRE wanted the research to continue, so Tom Kilburn , who was in his group at TRE, was seconded to the University of Manchester to continue the work with Freddie Williams on digital CRT storage. A Scientific Officer from TRE was also seconded full time to help him, initially Arthur Marsh, who left after a few months, and was replaced in the summer of 1947 by Geoff Tootill . "By March 1947 Tom Kilburn had discovered a different and better method of storing information, more suited to storing a large number of bits on the same tube.

By November 1947 they had succeeded in storing 2048 bits for a period of hours, having investigated a number of variations on storing a set of bits (dot-dash, dash-dot, defocus-focus, focus-defocus)" ( #tootill , accessed 10-09-2011). "The Williams tube tended to become unreliable with age, and most working installations had to be "tuned" by hand. By contrast, mercury delay line memory was slower and also needed hand tuning, but it did not age as badly and enjoyed some success in early digital electronic computing despite its data rate, weight, cost, thermal and toxicity problems. However, the Manchester Mark 1 was successfully commercialised as the Ferranti Mark 1. Some early computers in the USA also used the Williams tube, including the IAS machine, originally designed for Selectron tube memory, the UNIVAC 1103, IBM 701, IBM 702 and the Standards Western Automatic Computer (SWAC). Williams tubes were also used in the Soviet computer, Strela-1" (Wikipedia article on Williams Tube, accessed 10-09-2011).

After two years of research and development, on June 21, 1948 the Manchester Small Scale Experimental Machine ,or Manchester "Baby" prototype computer (Manchester Baby), ran its first program, written by Tom Kilburn . This small pilot version of a larger computer was the first stored-program electronic digital computer. It operated for only a short time. The machine was built at the Victoria University of Manchester in England by Frederic C. Williams , Tom Kilburn and Geoff Tootill to test the Williams-Kilburn cathode ray tube (CRT) memory (Williams tube). "The machine was not intended to be a practical computer but was instead designed as a testbed for the Williams tube, an early form of computer memory. Although considered 'small and primitive' by the standards of its time, it was the first working machine to contain all of the elements essential to a modern electronic computer. As soon as the SSEM had demonstrated the feasibility of its design, a project was initiated at the university to develop it into a more usable computer, the Manchester Mark 1. The Mark 1 in turn quickly became the prototype for the Ferranti Mark 1, the world's first commercially available general-purpose computer.

"The SSEM had a 32-bit word length and a memory of 32 words. As it was designed to be the simplest possible stored-program computer, the only arithmetic operations implemented in hardware were subtraction and negation; other arithmetic operations were implemented in software. The first of three programs written for the machine found the highest proper divisor of 218 (262,144), a calculation it was known would take a long time to run—and so prove the computer's reliability—by testing every integer from 218 − 1 downwards, as divisions had to be implemented by repeated subtractions of the divisor. The program consisted of 17 instructions and ran for 52 minutes before reaching the correct answer of 131,072, after the SSEM had performed 3.5 million operations (for an effective CPU speed of 1.1 kIPS)" (Wikipedia article Manchester Small Scale Experimental Machine, accessed 10-09-2011). You can watch a streaming video of a 1948 BBC newsreel about the Manchester "Baby" at this link .

[You will need to scroll down the web page.] None of the original Manchester Baby exists; however, a working replica 5.2 meters long and 1 ton in weight is on display at the Manchester Museum of Science and Industry (MOSI). In June 2013 its operation was demonstrated every Tuesday, Wednesday and Thursday from 11AM to 3PM. Happy Birthday, Baby—The 65th anniversary of computer software | Ars Technica Happy Birthday, Baby—The 65th anniversary of computer software A look back at the first decade of technology that led to the software revolution. Sean Gallagher - Jun 21, 2013 6:20 pm UTC A replica of the Manchester SSEM, aka "Baby"—now at the Museum of Science and Industry in Manchester, England. reader comments Share this story On June 21, 1948, at what was then known as the Victoria University of Manchester, software was born.

On that day 65 years ago, a proof-of-concept computer called "Baby"—officially designated as the Manchester Small Scale Experimental Machine—ran the first "program" retrieved not from paper tape or hard-set switches, but from random-access memory. Designed by Frederic C. Williams, Tom Kilburn, and Geoff Tootil, Baby wasn't the first programmable computer. But the technology proven in Baby, with its 1,024 bits of cathode-tube based RAM, would become the basis of the first commercial computers. In celebration of Baby's birthday, here's a look back at the first decade of computing and the computers that led to the birth of software and the computing revolution that would follow. The Z3, designed and built in 1941 by Konrad Zuse, was the first programmable computer. But it used 2,000 relays for all its functions, like those used in the phone switches of the time. It stored its programs on external tape. Used in statistical studies for aircraft engineering, the original Z3 was destroyed in 1943 during an Allied bombing raid on Berlin.

Designed by British engineer Tommy Flowers of the Post Office Research Station as a codebreaking machine, its first version, the Mark 1, was completed in 1943 using 1,500 tubes for processing rather than relays. An improved Mark 2, with 2,400 tubes (or "thermionic valves") was completed a year later. A total of 10 Colossus computers were built for use during World War II, but they were destroyed, along with the blueprints, to preserve the secrecy of the codebreaking program. This is a photo of one of the operations at Britain's cryptographic center at Bletchley Park. Enough details were left for the construction of a replica at Bletchley Park, now the home of the National Computing Museum. The first electronic "general purpose" computer, ENIAC was used to calculate ballistic tables for use in aiming US Army artillery. Designed by J. Presper Eckert and John Mauchly of the University of Pennsylvania'a Moore School of Electrical Engineering, the "Giant Brain" was unveiled in Philadelphia in February of 1946—too late to play a role in the war.

In 1947, ENIAC was moved to the Army's Aberdeen Proving Grounds, where it remained in operation until 1955. It used 17,468 vacuum tubes and was programmed through the use of switches and cables. Paul W Shaffer, curator of the University of Pennsylvania ENIAC Museum. "Baby," the Manchester Small-Scale Experimental Machine (SSEM), was the first "stored program" computer. Built at the Victoria University of Manchester, the SSEM was designed by Frederic C. Williams, Tom Kilburn, and Geoff Tootil as a proof-of-concept machine for a new type of computer memory developed by Williams and Kilburn—an early form of dynamic RAM based on a cathode ray tube. Parrot of Doom Programs run on Baby were set with a series of red input switches. Since it was just intended to be a test-bed, it could only perform subtraction and negation—if you wanted to add numbers, you needed to subtract their negative values. The results of programs run on Baby were output as a binary matrix of dots on a cathode ray tube. The success of Baby led to the Manchester Mark 1, completed in 1949.

The Mark 1 was programmed using code punched into paper tape and generated output using a "printer"—an International Telegraph Alphabet No. 2 (ITA2) teleprinter that encoded text as holes punched in paper tape. ITA2 is the predecessor of ASCII. Alan Turing developed a way to use ITA2's five-bit code to encode programs and output in base 32 and for the computer to convert base 32 to binary to run the program. The Mark 1 was the basis for the Ferranti Mark 1, the world's first commercial computer, which was released in 1951. The Ferranti also holds the distinction of being the first computer to generate music—it was programmed to play "Baa Baa Black Sheep" and "God Save the King" for a visit to Manchester by the BBC in 1951. 65 Years Ago, Manchester's 'Baby' Ran Electronically Stored Program - Slashdot Slashdot Check out the new SourceForge HTML5 internet speed test! No Flash necessary and runs on all devices.

× 47692131 story on Saturday June 22, 2013 @05:30AM from the blue-sapphire-anniversary-if-you're-wondering dept. hypnosec writes that the first ever practical implementation of the stored program concept took place 65 years ago, "as the Manchester Small Scale Experimental Machine aka 'Baby' became the world's first computer to run an electronically stored program on June 21, 1948. The 'Baby' was developed by Frederic C. Williams, Tom Kilburn and Geoff Tootill at the University of Manchester. 'Baby' served as a testbed for the experimental Williams-Kilburn tube – a cathode ray tube that was used to store binary digits, aka bits. The reason this became a milestone in computing history was that up until 'Baby' ran the first electronically stored program, there was no means of storing and accessing this information in a cost-effective and flexible way."

Question: The Manchester Small-Scale Experimental Machine, built by Frederic C. Williams, Tom Kilburn & Geoff Tootill that first ran on 21 June 1948, was an early form of what?
Answer: Computer