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On the left, the NEC TK 80 kit, based on Intel 8080 chip, on the centre, Busicom calculator motherboard, based on Intel 4004 chip, and on the right, the Busicom calculator, fully assembled in Ueno, Tokyo

Busicom was a Japanese calculator company. It owned the rights to the first commercial microprocessor, the Intel 4004, which began as the "Busicom Project" in 1968, before being developed as a single-chip microprocessor in partnership with Intel from 1969 to 1970.

Busicom asked Intel to design a set of integrated circuits for a new line of programmable electronic calculators in 1969.[1][2] In doing this, they spurred the invention of the first microprocessor to be commercialized,[3] the Intel 4004. Busicom owned the exclusive rights to the design and its components in 1970 but shared them with Intel in 1971.[4]

Two companies have done business as "Busicom" over the years; the Nippon Calculating Machine Corp, Ltd and subsequently Broughtons & Co.(Bristol) Ltd of the UK.

Nippon Calculating Machine Corporation, Ltd[]

The Unicom 141P and the NCR 18-36 were OEM versions of the Busicom 141-PF


The Nippon Calculating Machine Corp was incorporated in 1945 and changed its name in 1967 to Business Computer Corporation, Busicom. Due to a recession in Japan in 1974, Busicom became the first major Japanese company in the calculator industry to fail. Originally, they made Odhner type mechanical calculators and then moved on to electronic calculators always using state of the art designs. They made the first calculator with a microprocessor for their top of the line machines[5] and they were the first to make calculators with an all-in-one calculator chip, the Mostek MK6010, for their line of inexpensive machines.

One of their last mechanical calculators is the HL-21, an Odhner type machine.[6] Their first calculator with a microprocessor is the Busicom 141-PF. Their entry based calculators, the Busicom LE-120A (Handy-LE) and LE-120S (Handy),[7] were the first to fit in a pocket and also the first calculators to use an LED display.


In order to limit production cost, Busicom wanted to design a calculator engine that would be based on a few integrated circuits (ICs), containing some ROMs and shift registers and that could be adapted to a broad range of calculators by just changing the ROM IC chips. Busicom's engineers came up with a design that required 12 ICs.[8] In April 1968, engineer Masatoshi Shima was tasked with designing a special-purpose LSI chipset, along with his supervisor Tadashi Tanba, for use in the Busicom 141-PF desktop calculator.[9][10] This later became known as the "Busicom Project".[11] His initial design consisted of seven LSI chips, including a three-chip CPU.[11] His design included arithmetic units (adders), multiplier units, registers, read-only memory, and a macro-instruction set to control a decimal computer system.[9] Busicom then wanted a general-purpose LSI chipset, for not only desktop calculators, but also other equipment such as a teller machine, cash register and billing machine. Shima thus began work on a general-purpose LSI chipset in late 1968.[10]

People who were influential in the development of the microprocessor were Sharp engineer Tadashi Sasaki and Intel founder Robert Noyce. Sasaki conceived of a single-chip CPU in 1968, when he discussed the concept at a brainstorming meeting that was held in Japan. Sasaki attributes the basic invention to break the calculator chipset into four parts with ROM (4001), RAM (4002), shift registers (4003) and CPU (4004) to an unnamed woman, a software engineering researcher from Nara Women's College, who was present at the meeting. Sasaki then had his first meeting with Noyce in 1968, and presented the woman's four-division chipset concept to Intel and Busicom.[12]

In 1969, Busicom asked Intel, a company founded one year earlier in 1968 for the purpose of making solid state random-access memory (RAM), to finalize and manufacture their calculator engine. Intel, which was more of a memory company back then, had facilities to manufacture the high density silicon gate MOS chip Busicom required.[10] Shima went to Intel in June 1969 to present his design proposal. Due to Intel lacking logic engineers to understand the logic schematics or circuit engineers to convert them, Intel asked Shima to simplify the logic.[10] Intel wanted a single-chip CPU design,[10] influenced by Sharp's Tadashi Sasaki who presented the concept to Busicom and Intel in 1968.[12] The single-chip microprocessor design was then formulated by Intel's Ted Hoff in 1969,[11] simplifying Shima's initial design down to four chips, including a single-chip CPU.[11] Hoff was assigned to studying Busicom's design, and formulated a simpler, 4 ICs architecture centered on what was to become the 4004 microprocessor surrounded by a mixture of 3 different ICs containing ROM, shift registers, input/output ports and RAM—Intel's first product (1969) was the 3101 Schottky TTL bipolar 64-bit SRAM.[13]

Due to Hoff's formulation lacking key details, Shima came up with his own ideas to find solutions for its implementation. Shima was responsible for adding a 10-bit static shift register to make it useful as a printer's buffer and keyboard interface, many improvements in the instruction set, making the RAM organization suitable for a calculator, the memory address information transfer, the key program in an area of performance and program capacity, the functional specification, decimal computer idea, software, desktop calculator logic, real-time I/O control, and data exchange instruction between the accumulator and general purpose register. Hoff and Shima eventually realized the 4-bit microprocessor concept together, with the help of Intel's Stanley Mazor to interpret the ideas of Shima and Hoff.[10] The specifications of the four chips were developed over a period of a few months in 1969, between an Intel team led by Hoff and a Busicom team led by Shima.[11]

Busicom's management agreed to the new proposal,[14] and the chips' implementation was then led by Federico Faggin who had previously developed the Silicon Gate Technology at Fairchild Semiconductor. It was this technology that made the design of the microprocessor and the dynamic RAMs a reality. The 4 ICs were delivered to Busicom in January 1971.[15]

In mid-1971, Busicom, which had exclusive right to the design and its components, asked Intel to lower their prices.[4] Intel renegotiated their contract and Busicom gave up its exclusive rights to the chips.[4] A few months later, on November 15, 1971, Intel announced the immediate availability of the first microprocessor chipset family, the MCS-4 micro computer set (all from the Busicom design) with an advertisement in Electronic News.

Broughtons of Bristol[]

Broughtons of Bristol is a company selling and maintaining a broad line of business machines. They used to buy most of their equipment from Busicom and bought their trade name when they went bankrupt in 1974.

See also[]


  1. Augarten S.: Bit by Bit, page 261, Ticknor & Fields, 1984
  2. Stine, G.H., The Untold Story of the Computer Revolution, page 163, Arbor House, 1985
  3. Augarten S.: Bit by Bit, page 262-263, Ticknor & Fields, 1984
  4. 4.0 4.1 4.2 Reid, T.R.: The Chip, page 141-142, Simon and Schuster, 1984
  5. Busicom 141-FP
  6. Calculateur Busicom HL-21
  7. Pocket-size calculator Busicom LE-120A "HANDY-LE"
  8. Augarten S.: Bit by Bit, page 263-265, Ticknor & Fields, 1984
  9. 9.0 9.1 Nigel Tout. The Busicom 141-PF calculator and the Intel 4004 microprocessor. Retrieved on November 15, 2009.
  10. 10.0 10.1 10.2 10.3 10.4 10.5 Masatoshi Shima, IEEE
  11. 11.0 11.1 11.2 11.3 11.4 Federico Faggin, The Making of the First Microprocessor, IEEE Solid-State Circuits Magazine, Winter 2009, IEEE Xplore
  12. 12.0 12.1 Aspray, William (1994-05-25). Oral-History: Tadashi Sasaki. Interview #211 for the Center for the History of Electrical Engineering. The Institute of Electrical and Electronics Engineers, Inc.. Retrieved on 2013-01-02.
  13. 1969 - Schottky-Barrier Diode Doubles the Speed of TTL Memory & Logic Computer History Museum. Retrieved September 23, 2011.
  14. Agreement between Intel & NCM
  15. Faggin, Federico; Hoff, Marcian E.; Mazor, Stanley; Shima, Masatoshi (December 1996), "The History of the 4004", IEEE Micro (Los Alamitos: IEEE Computer Society) 16 (6): 10–19, Error: Bad DOI specified, ISSN 0272-1732 

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