Manchester Mark 1 - AbsoluteAstronomy.com

The Manchester Mark 1 was one of the earliest stored-program computer

Stored-program computer

A stored-program computer is one which stores program instructions in electronic memory. Often the definition is extended with the requirement that the treatment of programs and data in memory be interchangeable or uniform....

s, developed at the Victoria University of Manchester

Victoria University of Manchester

The Victoria University of Manchester was a university in Manchester, England. On 1 October 2004 it merged with the University of Manchester Institute of Science and Technology to form a new entity, "The University of Manchester".-1851 - 1951:The University was founded in 1851 as Owens College,...

from the Small-Scale Experimental Machine (SSEM) or "Baby" (operational in June 1948). It was also called the Manchester Automatic Digital Machine, or MADM. Work began in August 1948, and the first version was operational by April 1949; a program written to search for Mersenne primes ran error-free for nine hours on the night of 16/17 June 1949.

The machine's successful operation was widely reported in the British press, which used the phrase "electronic brain" in describing it to their readers. That description provoked a reaction from the head of the University of Manchester's Department of Neurosurgery, the start of a long-running debate as to whether an electronic computer could ever be truly creative.

The Mark 1 was initially developed to provide a computing resource within the university, to allow researchers to gain experience in the practical use of computers, but it very quickly also became a prototype on which the design of Ferranti

Ferranti

Ferranti or Ferranti International plc was a UK electrical engineering and equipment firm that operated for over a century from 1885 until it went bankrupt in 1993. Known primarily for defence electronics, the Company was once a constituent of the FTSE 100 Index but ceased trading in 1993.The...

's commercial version could be based. Development ceased at the end of 1949, and the machine was scrapped towards the end of 1950, replaced in February 1951 by a Ferranti Mark 1, the world's first commercially available general-purpose electronic computer.

The computer is especially historically significant because of its pioneering inclusion of index register

Index register

An index registerCommonly known as a B-line in early British computers. in a computer's CPU is a processor register used for modifying operand addresses during the run of a program, typically for doing vector/array operations...

s, an innovation which made it easier for a program to read sequentially through an array of words in memory. Thirty-four patents resulted from the machine's development, and many of the ideas behind its design were incorporated in subsequent commercial products such as the and 702

IBM 702

The IBM 702 was IBM's response to the UNIVAC—the first mainframe computer using magnetic tapes. Because these machines had less computational power than the IBM 701 and ERA 1103, which were favored for scientific computing, the 702 was aimed at business computing.The system used electrostatic...

as well as the Ferranti Mark 1. The chief designers, Frederic C. Williams

Frederic Calland Williams

Sir Frederic Calland Williams CBE, FRS , known as 'Freddie Williams', was an English engineer....

and Tom Kilburn

Tom Kilburn

Tom Kilburn CBE, FRS was an English engineer. With Freddie Williams he worked on the Williams Tube and the world's first stored-program computer, the Small-Scale Experimental Machine , while working at the University of Manchester.-Computer engineering:Kilburn was born in Dewsbury, Yorkshire and...

, concluded from their experiences with the Mark 1 that computers would be used more in scientific roles than in pure mathematics. In 1951 they started development work on Meg, the Mark 1's successor, which would include a floating point unit

Floating point unit

A floating-point unit is a part of a computer system specially designed to carry out operations on floating point numbers. Typical operations are addition, subtraction, multiplication, division, and square root...

Background

In 1936, mathematician Alan Turing

Alan Turing

Alan Mathison Turing, OBE, FRS , was an English mathematician, logician, cryptanalyst, and computer scientist. He was highly influential in the development of computer science, providing a formalisation of the concepts of "algorithm" and "computation" with the Turing machine, which played a...

published a definition of a theoretical "universal computing machine", a computer which held its program on tape, along with the data being worked on. Turing proved that such a machine was capable of solving any conceivable mathematical problem for which an algorithm

Algorithm

In mathematics and computer science, an algorithm is an effective method expressed as a finite list of well-defined instructions for calculating a function. Algorithms are used for calculation, data processing, and automated reasoning...

could be written. During the 1940s, Turing and others such as Konrad Zuse

Konrad Zuse

Konrad Zuse was a German civil engineer and computer pioneer. His greatest achievement was the world's first functional program-controlled Turing-complete computer, the Z3, which became operational in May 1941....

developed the idea of using the computer's own memory to hold both the program and data, instead of tape, but it was mathematician John von Neumann

John von Neumann

John von Neumann was a Hungarian-American mathematician and polymath who made major contributions to a vast number of fields, including set theory, functional analysis, quantum mechanics, ergodic theory, geometry, fluid dynamics, economics and game theory, computer science, numerical analysis,...

who became widely credited with defining that stored-program computer architecture

Stored-program computer

, on which the Manchester Mark 1 was based.

The practical construction of a von Neumann computer depended on the availability of a suitable memory device. The University of Manchester

University of Manchester

The University of Manchester is a public research university located in Manchester, United Kingdom. It is a "red brick" university and a member of the Russell Group of research-intensive British universities and the N8 Group...

's Small-Scale Experimental Machine

Small-Scale Experimental Machine

The Manchester Small-Scale Experimental Machine , nicknamed Baby, was the world's first stored-program computer. It was built at the Victoria University of Manchester by Frederic C...

(SSEM), the world's first stored-program computer, had successfully demonstrated the practicality of the stored-program approach and of the Williams tube

Williams tube

The Williams tube or the Williams-Kilburn tube , developed in about 1946 or 1947, was a cathode ray tube used to electronically store binary data....

, an early form of computer memory based on a standard cathode ray tube

Cathode ray tube

The cathode ray tube is a vacuum tube containing an electron gun and a fluorescent screen used to view images. It has a means to accelerate and deflect the electron beam onto the fluorescent screen to create the images. The image may represent electrical waveforms , pictures , radar targets and...

(CRT), by running its first program in June 1948. Early electronic computers were generally programmed by being rewired, or via plugs and patch panels

Patch panel

A patch panel or patch bay is a panel, typically rackmounted, that houses cable connections. One typically shorter patch cable will plug into the front side, whereas the back holds the connection of a much longer and more permanent cable...

; there was no separate program stored in memory, as in a modern computer. It could take several days to reprogram ENIAC

ENIAC

ENIAC was the first general-purpose electronic computer. It was a Turing-complete digital computer capable of being reprogrammed to solve a full range of computing problems....

, for instance. Stored-program computers were also being developed by other researchers, notably the National Physical Laboratory's Pilot ACE

Pilot ACE

The Pilot ACE was one of the first computers built in the United Kingdom, at the National Physical Laboratory in the early 1950s.It was a preliminary version of the full ACE, which had been designed by Alan Turing. After Turing left NPL , James H...

, Cambridge University

University of Cambridge

The University of Cambridge is a public research university located in Cambridge, United Kingdom. It is the second-oldest university in both the United Kingdom and the English-speaking world , and the seventh-oldest globally...

's EDSAC

EDSAC

Electronic Delay Storage Automatic Calculator was an early British computer. The machine, having been inspired by John von Neumann's seminal First Draft of a Report on the EDVAC, was constructed by Maurice Wilkes and his team at the University of Cambridge Mathematical Laboratory in England...

, and US Army's EDVAC

EDVAC

EDVAC was one of the earliest electronic computers. Unlike its predecessor the ENIAC, it was binary rather than decimal, and was a stored program computer....

. The SSEM and the Mark 1 differed primarily in their use of Williams tube

Williams tube

The Williams tube or the Williams-Kilburn tube , developed in about 1946 or 1947, was a cathode ray tube used to electronically store binary data....

s as memory devices, instead of mercury delay line

Delay line memory

Delay line memory was a form of computer memory used on some of the earliest digital computers. Like many modern forms of electronic computer memory, delay line memory was a refreshable memory, but as opposed to modern random-access memory, delay line memory was serial-access...

s.

From about August 1948, the SSEM was intensively developed as a prototype for the Manchester Mark 1, initially with the aim of providing the university with a more realistic computing facility. In October 1948, UK Government Chief Scientist Ben Lockspeiser

Ben Lockspeiser

Sir Benjamin Lockspeiser KCB, FRS, MIMechE, FRAeS, was a British scientific administrator and the first President of CERN....

was given a demonstration of the prototype Mark 1 while on a visit to the University of Manchester. Lockspeiser was so impressed by what he saw that he immediately initiated a government contract with the local firm of Ferranti

Ferranti

to make a commercial version of the machine, the Ferranti Mark 1. In his letter to the company, dated 26 October 1948, Lockspeiser authorised the company to "proceed on the lines we discussed, namely, to construct an electronic calculating machine to the instructions of Professor F. C. Williams". From that point on, development of the Mark 1 had the additional purpose of supplying Ferranti with a design on which to base their commercial machine. The government's contract with Ferranti ran for five years from November 1948, and involved an estimated £35,000 per year (£ as of ).

Development and design

The SSEM had been designed by the team of Frederic C. Williams

Frederic Calland Williams

Sir Frederic Calland Williams CBE, FRS , known as 'Freddie Williams', was an English engineer....

, Tom Kilburn

Tom Kilburn

and Geoff Tootill. To develop the Mark 1 they were joined by two research students, D. B. G. Edwards and G. E. Thomas; work began in earnest in August 1948. The project soon had the dual purpose of supplying Ferranti with a working design on which they could base a commercial machine, the Ferranti Mark 1, and of building a computer that would allow researchers to gain experience of how such a machine could be used in practice. The first of the two versions of the Manchester Mark 1 – known as the Intermediary Version – was operational by April 1949. However, this first version lacked features such as the instructions necessary to programmatically transfer data between the main store and its newly developed magnetic backing store, which had to be done by halting the machine and manually initiating the transfer. These missing features were incorporated in the Final Specification version, which was fully working by October 1949. The machine contained 4,050 valve

Vacuum tube

In electronics, a vacuum tube, electron tube , or thermionic valve , reduced to simply "tube" or "valve" in everyday parlance, is a device that relies on the flow of electric current through a vacuum...

s and had a power consumption of 25 kilowatts

Watt

The watt is a derived unit of power in the International System of Units , named after the Scottish engineer James Watt . The unit, defined as one joule per second, measures the rate of energy conversion.-Definition:...

. To increase reliability, purpose-built CRTs made by GEC were used in the machine instead of the standard devices used in the SSEM.

The SSEM's 32-bit word length was increased to 40 bit

Bit

A bit is the basic unit of information in computing and telecommunications; it is the amount of information stored by a digital device or other physical system that exists in one of two possible distinct states...

s. Each word could hold either one 40-bit number or two 20-bit program instructions. The main store consisted of two Williams tubes each holding an array of 32 x 40-bit words – known as a page

Page (computing)

A page, memory page, or virtual page is a fixed-length contiguous block of virtual memory that is the smallest unit of data for the following:* memory allocation performed by the operating system for a program; and...

– backed up by a magnetic drum capable of storing an additional 32 pages; the capacity was increased to 128 pages in the Final Specification version. The 12 inches (30.5 cm) diameter drum, initially known as a magnetic wheel, contained a series of parallel magnetic tracks around its surface, each with its own read/write head. Each track held 2,560 bits, corresponding to 2 pages (2 x 32 x 40 bits). One revolution of the drum took 30 milliseconds, during which time both pages could be transferred to the CRT

Cathode ray tube

main memory, although the actual data transfer time depended on the latency, the time it took for a page to arrive under the read/write head. Writing pages to the drum took about twice as long as reading. The drum's rotational speed was synchronised to the main central processor clock

Clock rate

The clock rate typically refers to the frequency that a CPU is running at.For example, a crystal oscillator frequency reference typically is synonymous with a fixed sinusoidal waveform, a clock rate is that frequency reference translated by electronic circuitry into a corresponding square wave...

, which allowed for additional drums to be added. Data was recorded onto the drum using a phase modulation

Phase modulation

Phase modulation is a form of modulation that represents information as variations in the instantaneous phase of a carrier wave.Unlike its more popular counterpart, frequency modulation , PM is not very widely used for radio transmissions...

technique still known today as Manchester coding

Manchester code

In telecommunication and data storage, Manchester code is a line code in which the encoding of each data bit has at least one transition and occupies the same time...

.

The machine's instruction set

Instruction set

An instruction set, or instruction set architecture , is the part of the computer architecture related to programming, including the native data types, instructions, registers, addressing modes, memory architecture, interrupt and exception handling, and external I/O...

was increased from the 7 of the SSEM to 26 initially, including multiplication done in hardware. This increased to 30 instructions in the Final Specification version. Ten bits of each word were allocated to hold the instruction code

Instruction set

. The standard instruction time was 1.8 milliseconds, but multiplication was much slower, depending on the size of the operand

Operand

In mathematics, an operand is the object of a mathematical operation, a quantity on which an operation is performed.-Example :The following arithmetic expression shows an example of operators and operands:3 + 6 = 9\;...

.

The machine's most significant innovation is generally considered to be its incorporation of index registers, commonplace on modern computers. The SSEM had included two registers, implemented as Williams tubes; the accumulator

Accumulator (computing)

In a computer's central processing unit , an accumulator is a register in which intermediate arithmetic and logic results are stored. Without a register like an accumulator, it would be necessary to write the result of each calculation to main memory, perhaps only to be read right back again for...

(A) and the program counter

Program counter

The program counter , commonly called the instruction pointer in Intel x86 microprocessors, and sometimes called the instruction address register, or just part of the instruction sequencer in some computers, is a processor register that indicates where the computer is in its instruction sequence...

(C). As A and C had already been assigned, the tube holding the two index registers, originally known as B-lines, was given the name B. The contents of the registers could be used to modify program instructions, allowing convenient iteration through an array of numbers stored in memory. The Mark 1 also had a fourth tube, (M), to hold the multiplicand

Multiplication

Multiplication is the mathematical operation of scaling one number by another. It is one of the four basic operations in elementary arithmetic ....

and multiplier for a multiplication operation.

Programming

Of the 20 bits allocated for each program instruction, 10 were used to hold the instruction code

Instruction set

, which allowed for 1,024 (2¹⁰) different instructions. The machine had 26 initially, increasing to 30 when the function codes to programmatically control the data transfer between the magnetic drum and the cathode ray tube (CRT) main store were added. On the Intermediary Version programs were input by key switches, and the output was displayed as a series of dots and dashes on a cathode ray tube known as the output device, just as on the SSEM from which the Mark 1 had been developed. However, the Final Specification machine, completed in October 1949, benefitted from the addition of a teleprinter

Teleprinter

A teleprinter is a electromechanical typewriter that can be used to communicate typed messages from point to point and point to multipoint over a variety of communication channels that range from a simple electrical connection, such as a pair of wires, to the use of radio and microwave as the...

with a 5-hole paper-tape reader and punch

Punched tape

Punched tape or paper tape is an obsolete form of data storage, consisting of a long strip of paper in which holes are punched to store data...

.

Mathematician Alan Turing

Alan Turing

, who had been appointed to the nominal post of Deputy Director of the Computing Machine Laboratory at the University of Manchester in September 1948, devised a base 32 encoding scheme based on the standard ITA2 5-bit teleprinter code, which allowed programs and data to be written to and read from paper tape. The ITA2 system maps each of the possible 32 binary values that can be represented in 5 bits (2⁵) to a single character. Thus "10010" represents "D", "10001" represents "Z", and so forth. Turing changed only a few of the standard encodings; for instance, 00000 and 01000, which mean "no effect" and "linefeed" in the teleprinter code, were represented by the characters "/" and "@" respectively. Binary zero, represented by the forward slash, was the most common character in programs and data, leading to sequences written as "///////////////". One early user suggested that Turing's choice of a forward slash was a subconscious choice on his part, a representation of rain seen through a dirty window, reflecting Manchester's "famously dismal" weather.

Because the Mark 1 had a 40-bit word length, eight 5-bit teleprinter characters were required to encode each word. Thus for example the binary word:
10001 10010 10100 01001 10001 11001 01010 10110 would be represented on paper tape as ZDSLZWRF. The contents of any word in store could also be set via the teleprinter's keyboard, and output onto its printer. The machine worked internally in binary, but it was able to carry out the necessary decimal to binary and binary to decimal conversions for its input and output respectively.

There was no assembly language

Assembly language

An assembly language is a low-level programming language for computers, microprocessors, microcontrollers, and other programmable devices. It implements a symbolic representation of the machine codes and other constants needed to program a given CPU architecture...

defined for the Mark 1. Programs had to be written and submitted in binary form, encoded as eight 5-bit characters for each 40-bit word; programmers were encouraged to memorize the modified ITA2 coding scheme to make their job easier. Data was read and written from the papertape punch under program control. The Mark 1 had no system of hardware interrupt

Interrupt

In computing, an interrupt is an asynchronous signal indicating the need for attention or a synchronous event in software indicating the need for a change in execution....

s; the program continued after a read or write operation had been initiated until another input/output instruction was encountered, at which point the machine waited for the first to complete.

The Mark 1 had no operating system

Operating system

An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...

; its only system software was a few basic routines for input and output. As in the SSEM from which it was developed, and in contrast to the established mathematical convention, the machine's storage was arranged with the least significant digits to the left; thus a one was represented in five bits as "10000", rather than the more conventional "00001". Negative numbers were represented using two's complement

Two's complement

The two's complement of a binary number is defined as the value obtained by subtracting the number from a large power of two...

, as most computers still do today. 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 40-bit word was −2³⁹ to +2³⁹ − 1 (decimal: -549,755,813,888 to +549,755,813,887).

First programs

The first realistic program to be run on the Mark 1 was a search for Mersenne primes, in early April 1949, which ran error free for nine hours on the night of 16/17 June 1949. The algorithm was specified by Max Newman

Max Newman

Maxwell Herman Alexander "Max" Newman, FRS was a British mathematician and codebreaker.-Pre–World War II:Max Newman was born Maxwell Neumann in Chelsea, London, England, on 7 February 1897...

, head of the Mathematics Department at the University of Manchester, and the program was written by Kilburn and Tootill. Turing later wrote an optimised version of the program, dubbed the Mersenne Express.

The Manchester Mark 1 continued to do useful mathematical work between 1949 and 1950, including an investigation of the Riemann hypothesis

Riemann hypothesis

In mathematics, the Riemann hypothesis, proposed by , is a conjecture about the location of the zeros of the Riemann zeta function which states that all non-trivial zeros have real part 1/2...

and calculations in optics.

Later developments

Tootill was temporarily transferred from the University of Manchester to Ferranti in August 1949 to continue work on the Ferranti Mark 1's design, and spent four months working with the company. The Manchester Mark 1 was dismantled and scrapped towards the end of 1950, replaced a few months later by the first Ferranti Mark 1, the world's first commercially available general-purpose computer.

Between 1946 and 1949 the average size of the design team working on the Mark 1 and its predecessor, the SSEM, was about four people. During that time 34 patents were taken out based on the team's work, either by the Ministry of Supply

Ministry of Supply

The Ministry of Supply was a department of the UK Government formed in 1939 to co-ordinate the supply of equipment to all three British armed forces, headed by the Minister of Supply. There was, however, a separate ministry responsible for aircraft production and the Admiralty retained...

or by its successor, the National Research Development Corporation

National Research Development Corporation

The National Research Development Corporation was a non-departmental government body established by the British Government to transfer technology from the public sector to the private sector.-History:...

. In July 1949 IBM

IBM

International Business Machines Corporation or IBM is an American multinational technology and consulting corporation headquartered in Armonk, New York, United States. IBM manufactures and sells computer hardware and software, and it offers infrastructure, hosting and consulting services in areas...

invited Williams to the United States on an all-expenses-paid trip to discuss the Mark 1's design. The company subsequently licensed several of the patented ideas developed for the machine, including the Williams tube, in the design of its own 701

IBM 701

The IBM 701, known as the Defense Calculator while in development, was announced to the public on April 29, 1952, and was IBM’s first commercial scientific computer...

and 702

IBM 702

computers. The most significant design legacy of the Manchester Mark 1 was perhaps its incorporation of index registers, the patent for which was taken out in the names of Williams, Kilburn, Tootill, and Newman.

Kilburn and Williams concluded that computers would be used more in scientific roles than pure maths, and decided to develop a new machine which would include a floating point unit

Floating point unit

. Work began in 1951. The resulting machine, which ran its first program in May 1954, was known as Meg, or the megacycle machine. It was smaller and simpler than the Mark 1, as well as much faster for maths problems. Ferranti

Ferranti

produced a version of Meg with the Williams tubes replaced by the more reliable core memory. The resulting design was sold as the Ferranti Mercury

Ferranti Mercury

The Mercury was an early 1950s commercial computer built by Ferranti. It was the successor to the Ferranti Mark 1, adding a floating point unit for improved performance, and increased reliability by replacing the Williams tube memory with core memory and using more solid state components...

Cultural impact

The successful operation of the Manchester Mark 1 and its predecessor, the SSEM, was widely reported in the British press, which used the phrase "electronic brain" to describe the machines. Lord Louis Mountbatten

Louis Mountbatten, 1st Earl Mountbatten of Burma

Admiral of the Fleet Louis Francis Albert Victor Nicholas George Mountbatten, 1st Earl Mountbatten of Burma, KG, GCB, OM, GCSI, GCIE, GCVO, DSO, PC, FRS , was a British statesman and naval officer, and an uncle of Prince Philip, Duke of Edinburgh...

had earlier introduced that term in a speech delivered to the British Institution of Radio Engineers on 31 October 1946, in which he speculated about how the primitive computers then available might evolve. The excitement surrounding the reporting in 1949 of what was the first recognisably modern computer provoked a reaction unexpected by its developers; Sir Geoffrey Jefferson

Geoffrey Jefferson

Sir Geoffrey Jefferson FRS was a British neurologist and pioneering neurosurgeon. He was educated in Manchester, England, obtaining his medical degree in 1909. He became a fellow of the Royal College of Surgeons two years later. He married in 1914, and moved to Canada...

, professor of neurosurgery at the University of Manchester, on being asked to deliver the Lister Oration on 9 June 1949 chose "The Mind of Mechanical Man" as his subject. His purpose was to "debunk" the Manchester project. In his address he said:

The Times
The Times
The Times is a British daily national newspaper, first published in London in 1785 under the title The Daily Universal Register . The Times and its sister paper The Sunday Times are published by Times Newspapers Limited, a subsidiary since 1981 of News International...

reported on Jefferson's speech the following day, adding that Jefferson forecast that "the day would never dawn when the gracious rooms of the Royal Society would be converted into garages to house these new fellows". This was interpreted as a deliberate slight to Newman, who had secured a grant from the society to continue the work of the Manchester team. In response he wrote a follow-up article for The Times, in which he claimed that there was a close analogy between the structure of the Mark 1 and the human brain. Newman's article included an interview with Turing, who added:

External links

The Manchester Mark 1
Early computers at Manchester University in Resurrection (The Bulletin of the Computer Conservation Society) 1 (4), Summer 1992, ISSN 0958-7403

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