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Harvard Mark I

Harvard Mark I

Overview


The IBM Automatic Sequence Controlled Calculator (ASCC), called the Mark I by Harvard University
Harvard University
Harvard University is a private Ivy League university located in Cambridge, Massachusetts, United States, established in 1636 by the Massachusetts legislature. Harvard is the oldest institution of higher learning in the United States and the first corporation chartered in the country...

, was an electro
Electronics
Electronics is the branch of science, engineering and technology that deals with electrical circuits involving active electrical components such as vacuum tubes, transistors, diodes and integrated circuits, and associated passive interconnection technologies...

-mechanical
Machine
A machine manages power to accomplish a task, examples include, a mechanical system, a computing system, an electronic system, and a molecular machine. In common usage, the meaning is that of a device having parts that perform or assist in performing any type of work...

 computer
Computer
A computer is a programmable machine designed to sequentially and automatically carry out a sequence of arithmetic or logical operations. The particular sequence of operations can be changed readily, allowing the computer to solve more than one kind of problem...

.

The electromechanical ASCC was devised by Howard H. Aiken, built at 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...

 and shipped to Harvard in February 1944. It began computations for the U.S. Navy Bureau of Ships in May and was officially presented to the university on August 7, 1944. It was very reliable, much more so than early electronic computers.
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Encyclopedia


The IBM Automatic Sequence Controlled Calculator (ASCC), called the Mark I by Harvard University
Harvard University
Harvard University is a private Ivy League university located in Cambridge, Massachusetts, United States, established in 1636 by the Massachusetts legislature. Harvard is the oldest institution of higher learning in the United States and the first corporation chartered in the country...

, was an electro
Electronics
Electronics is the branch of science, engineering and technology that deals with electrical circuits involving active electrical components such as vacuum tubes, transistors, diodes and integrated circuits, and associated passive interconnection technologies...

-mechanical
Machine
A machine manages power to accomplish a task, examples include, a mechanical system, a computing system, an electronic system, and a molecular machine. In common usage, the meaning is that of a device having parts that perform or assist in performing any type of work...

 computer
Computer
A computer is a programmable machine designed to sequentially and automatically carry out a sequence of arithmetic or logical operations. The particular sequence of operations can be changed readily, allowing the computer to solve more than one kind of problem...

.

The electromechanical ASCC was devised by Howard H. Aiken, built at 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...

 and shipped to Harvard in February 1944. It began computations for the U.S. Navy Bureau of Ships in May and was officially presented to the university on August 7, 1944. It was very reliable, much more so than early electronic computers. It has been described as "the beginning of the era of the modern computer" and "the real dawn of the computer age".

Design and construction


The ASCC was built from switch
Switch
In electronics, a switch is an electrical component that can break an electrical circuit, interrupting the current or diverting it from one conductor to another....

es, relay
Relay
A relay is an electrically operated switch. Many relays use an electromagnet to operate a switching mechanism mechanically, but other operating principles are also used. Relays are used where it is necessary to control a circuit by a low-power signal , or where several circuits must be controlled...

s, rotating shaft
Pinwheel calculator
A Pinwheel calculator was a class of mechanical calculator popular in the 19th and 20th century using, for its calculating engine, a set of wheels that had an adjustable number of teeth...

s, and clutch
Clutch
A clutch is a mechanical device which provides for the transmission of power from one component to another...

es. It used 765,000 component
Electronic component
An electronic component is a basic electronic element and may be available in a discrete form having two or more electrical terminals . These are intended to be connected together, usually by soldering to a printed circuit board, in order to create an electronic circuit with a particular function...

s and hundreds of miles of wire, comprising a volume of 51 feet (16 m) in length, eight feet (2.4 m) in height, and two feet (~61 cm) deep. It had a weight of about 10,000 pounds (4500 kg). The basic calculating units had to be synchronized mechanically, so they were run by a 50-foot (~15.5 m) shaft driven by a five-horsepower (4 kW) electric motor. From the IBM Archives:
The Automatic Sequence Controlled Calculator (Harvard Mark I) was the first operating machine that could execute long computations automatically. A project conceived by Harvard University's Dr. Howard Aiken, the Mark I was built by IBM engineers in Endicott, N.Y. A steel frame 51 feet (15.5 m) long and eight feet high held the calculator, which consisted of an interlocking panel of small gears, counters, switches and control circuits, all only a few inches in depth. The ASCC used 500 miles (804.7 km) of wire with three million connections, 3,500 multipole relays with 35,000 contacts, 2,225 counters, 1,464 tenpole switches and tiers of 72 adding machines, each with 23 significant numbers. It was the industry's largest electromechanical calculator.


The enclosure for the Mark I was designed by futuristic American industrial designer Norman Bel Geddes
Norman Bel Geddes
Norman Melancton Bel Geddes was an American theatrical and industrial designer who focused on aerodynamics....

. Aiken considered the elaborate case to be a waste of resources, since computing power was in high demand during the war and the funds ($50,000 or more according to Grace Hopper
Grace Hopper
Rear Admiral Grace Murray Hopper was an American computer scientist and United States Navy officer. A pioneer in the field, she was one of the first programmers of the Harvard Mark I computer, and developed the first compiler for a computer programming language...

) could have been used to build additional computer equipment.

Operation


The Mark I had 60 sets of 24 switches for manual data entry and could store 72 numbers, each 23 decimal digits long. It could do three additions or subtractions in a second. A multiplication took six seconds, a division took 15.3 seconds, and a logarithm or a trigonometric function took over one minute.

The Mark I read its instruction
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...

s from a 24 channel punched paper tape
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...

 and executed the current instruction and then read in the next one. It had no conditional branch instruction. This meant that complex programs had to be physically long. A loop was accomplished by joining the end of the paper tape containing the program back to the beginning of the tape (literally creating a loop). This separation of data and instructions is known as the Harvard architecture
Harvard architecture
The Harvard architecture is a computer architecture with physically separate storage and signal pathways for instructions and data. The term originated from the Harvard Mark I relay-based computer, which stored instructions on punched tape and data in electro-mechanical counters...

 (although the exact nature of this separation that makes a machine Harvard, rather than Von Neumann, has been obscured with the passage of time, see Modified Harvard architecture
Modified Harvard architecture
The Modified Harvard Architecture is a variation of the Harvard computer architecture that allows the contents of the instruction memory to be accessed as if it were data...

). The first programmers of the Mark I were computing pioneers Richard Milton Block, Robert Campbell, and Grace Hopper
Grace Hopper
Rear Admiral Grace Murray Hopper was an American computer scientist and United States Navy officer. A pioneer in the field, she was one of the first programmers of the Harvard Mark I computer, and developed the first compiler for a computer programming language...

.

Instruction format


The 24 channels of the input tape were divided into 3 fields of 8 channels. Each 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...

, each set of switches, and the registers
Hardware register
In digital electronics, especially computing, a hardware register stores bits of information, in a way that all the bits can be written to or read out simultaneously.The hardware registers inside a central processing unit are called processor registers....

 associated with the input, output
Input/output
In computing, input/output, or I/O, refers to the communication between an information processing system , and the outside world, possibly a human, or another information processing system. Inputs are the signals or data received by the system, and outputs are the signals or data sent from it...

, and arithmetic units
Arithmetic logic unit
In computing, an arithmetic logic unit is a digital circuit that performs arithmetic and logical operations.The ALU is a fundamental building block of the central processing unit of a computer, and even the simplest microprocessors contain one for purposes such as maintaining timers...

 were assigned a unique identifying index number. These numbers were represented in binary
Binary numeral system
The binary numeral system, or base-2 number system, represents numeric values using two symbols, 0 and 1. More specifically, the usual base-2 system is a positional notation with a radix of 2...

 on the control tape. The first field was the binary index of the result of the operation and the second, the source datum for the operation. The third field was a code
Opcode
In computer science engineering, an opcode is the portion of a machine language instruction that specifies the operation to be performed. Their specification and format are laid out in the instruction set architecture of the processor in question...

 for the operation to be performed.

Aiken and IBM


Aiken published a press release announcing the Mark I listing himself as the sole "inventor".
James W. Bryce
James W. Bryce
James Wares Bryce was an American engineer and inventor. In 1936, on the centenary of the United States Patent Office, he was honored as one of the country’s 10 greatest living inventors....

 was the only IBM person mentioned, even though several IBM engineers including Clair Lake and Frank Hamilton had helped to build various elements. Thomas J. Watson
Thomas J. Watson
Thomas John Watson, Sr. was president of International Business Machines , who oversaw that company's growth into an international force from 1914 to 1956...

 was enraged, and only reluctantly attended the dedication ceremony on August 7, 1944. Aiken, in turn, decided to build further machines without IBM's help, and the ASCC came to be generally known as the Harvard Mark I.
IBM went on to build the Selective Sequence Electronic Calculator (SSEC) to both test new technology and provide more publicity for the company.

Successors


The Mark I was followed by the Harvard Mark II
Harvard Mark II
The Harvard Mark II was an electromechanical computer built at Harvard University under the direction of Howard Aiken and was finished in 1947. It was financed by the United States Navy....

 (1947 or 1948), Mark III/ADEC
Harvard Mark III
The Harvard Mark III, also known as ADEC was an early computer that was partially electronic and partially electromechanical. It was built at Harvard University under the supervision of Howard Aiken for the US Navy.The Mark III's word consisted of 16 bits. It used 5,000 vacuum tubes and 1,500...

 (September 1949), and Harvard Mark IV
Harvard Mark IV
The Harvard Mark IV was an electronic stored-program computer built by Harvard University under the supervision of Howard Aiken for the United States Air Force. The computer was finished being built in 1952. It stayed at Harvard, where the Air Force used it extensively.The Mark IV was all electronic...

 (1952) – all the work of Aiken. The Mark II was an improvement over the Mark I, but it also used electromechanical relays. The Mark III used mostly electronic components, using vacuum tubes and crystal diodes, and the Mark IV was all-electronic, using solid state
Solid state (electronics)
Solid-state electronics are those circuits or devices built entirely from solid materials and in which the electrons, or other charge carriers, are confined entirely within the solid material...

 components. The Mark III and Mark IV used magnetic drum
Drum memory
Drum memory is a magnetic data storage device and was an early form of computer memory widely used in the 1950s and into the 1960s, invented by Gustav Tauschek in 1932 in Austria....

 memory and the Mark IV also had magnetic core memory
Magnetic core memory
Magnetic-core memory was the predominant form of random-access computer memory for 20 years . It uses tiny magnetic toroids , the cores, through which wires are threaded to write and read information. Each core represents one bit of information...

. The Mark II and Mark III went to the US Navy
United States Navy
The United States Navy is the naval warfare service branch of the United States Armed Forces and one of the seven uniformed services of the United States. The U.S. Navy is the largest in the world; its battle fleet tonnage is greater than that of the next 13 largest navies combined. The U.S...

 base at Dahlgren, Virginia
Dahlgren, Virginia
Dahlgren is a census-designated place in King George County, Virginia, United States. The population was 997 at the 2000 census. The community is located within the Northern Neck George Washington Birthplace American Viticultural Area winemaking appellation established by the United States...

. The Mark IV was built for the US Air Force
United States Air Force
The United States Air Force is the aerial warfare service branch of the United States Armed Forces and one of the American uniformed services. Initially part of the United States Army, the USAF was formed as a separate branch of the military on September 18, 1947 under the National Security Act of...

, but it stayed at Harvard.

The Mark I was eventually disassembled, although portions of it remain at Harvard in the Science Center. It is part of the Harvard Collection of Historical Scientific Instruments.

See also

  • History of computing hardware
    History of computing hardware
    The history of computing hardware is the record of the ongoing effort to make computer hardware faster, cheaper, and capable of storing more data....

  • Harvard Mark II
    Harvard Mark II
    The Harvard Mark II was an electromechanical computer built at Harvard University under the direction of Howard Aiken and was finished in 1947. It was financed by the United States Navy....

  • Harvard Mark III
    Harvard Mark III
    The Harvard Mark III, also known as ADEC was an early computer that was partially electronic and partially electromechanical. It was built at Harvard University under the supervision of Howard Aiken for the US Navy.The Mark III's word consisted of 16 bits. It used 5,000 vacuum tubes and 1,500...

  • Harvard Mark IV
    Harvard Mark IV
    The Harvard Mark IV was an electronic stored-program computer built by Harvard University under the supervision of Howard Aiken for the United States Air Force. The computer was finished being built in 1952. It stayed at Harvard, where the Air Force used it extensively.The Mark IV was all electronic...

  • Howard Aiken
    Howard Aiken
    Howard Hathaway Aiken was a pioneer in computing, being the original conceptual designer behind IBM's Harvard Mark I computer....

  • Other early computers:
    • Zuse Z3 (Germany)
    • Manchester Mark 1
      Manchester Mark 1
      The Manchester Mark 1 was one of the earliest stored-program computers, developed at the Victoria University of Manchester from the Small-Scale Experimental Machine or "Baby" . It was also called the Manchester Automatic Digital Machine, or MADM...

       (UK)
    • Atanasoff–Berry Computer (USA)
    • 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....

       (USA)
    • Colossus
      Colossus computer
      Not to be confused with the fictional computer of the same name in the movie Colossus: The Forbin Project.Colossus was the world's first electronic, digital, programmable computer. Colossus and its successors were used by British codebreakers to help read encrypted German messages during World War II...

       (UK)
    • IBM Selective Sequence Electronic Calculator (USA)

External links


  • Oral history interview with Robert Hawkins at Charles Babbage Institute
    Charles Babbage Institute
    The Charles Babbage Institute is a research center at the University of Minnesota specializing in the history of information technology, particularly the history since 1935 of digital computing, programming/software, and computer networking....

    , University of Minnesota, Minneapolis. Hawkins discusses the Harvard-IBM Mark I project that he worked on at Harvard University as a technician as well as Howard Aiken
    Howard Aiken
    Howard Hathaway Aiken was a pioneer in computing, being the original conceptual designer behind IBM's Harvard Mark I computer....

    's leadership of the project.
  • Oral history interview with Richard M. Bloch at Charles Babbage Institute
    Charles Babbage Institute
    The Charles Babbage Institute is a research center at the University of Minnesota specializing in the history of information technology, particularly the history since 1935 of digital computing, programming/software, and computer networking....

    , University of Minnesota, Minneapolis. Bloch describes his work at the Harvard Computation Laboratory for Howard Aiken
    Howard Aiken
    Howard Hathaway Aiken was a pioneer in computing, being the original conceptual designer behind IBM's Harvard Mark I computer....

     on the Mark I.
  • Oral history interview with Robert V. D. Campbell at Charles Babbage Institute
    Charles Babbage Institute
    The Charles Babbage Institute is a research center at the University of Minnesota specializing in the history of information technology, particularly the history since 1935 of digital computing, programming/software, and computer networking....

    , University of Minnesota, Minneapolis. Campbell discusses the contributions of Harvard and IBM to the Mark I project.
  • IBM Archive: IBM ASCC Reference Room
  • ASCC operational manual (PDF)