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BINAC

The BINAC (Binary Automatic Computer) was the first electronic stored-program computer constructed in the United States, developed as a general-purpose machine by engineers J. Presper Eckert and John W. Mauchly through their newly founded Eckert-Mauchly Computer Corporation.^[1]^[2] Completed in August 1949 after a contract awarded in October 1947 by Northrop Aircraft to explore airborne navigation for guided missiles, it represented a pivotal advancement in computing following their earlier ENIAC project at the University of Pennsylvania's Moore School.^[1]^[3] BINAC's design incorporated vacuum tube technology typical of first-generation computers (1946–1954) and drew from stored-program principles outlined in the EDVAC report, enabling flexible programming without rewiring.^[3] The system featured two independent serial processors, each approximately 5 feet tall, 4 feet long, and 1 foot wide, with around 700 vacuum tubes per unit for a total of about 1,400 tubes.^[1] Its memory consisted of mercury delay lines storing 512 31-bit words per processor, and it achieved computational speeds of up to 3,500 additions and 1,000 multiplications per second.^[1]^[2] Despite its innovative architecture, BINAC faced significant development hurdles, including a 15-month delay beyond schedule and an overrun of $178,000 on the budget, compounded by reliability issues such as a 25% vacuum tube failure rate and erratic performance influenced by environmental factors like humidity.^[1] Northrop ultimately deemed the project economically unfeasible and declined delivery, leading Eckert and Mauchly to repurpose its components for their subsequent UNIVAC system, which became the first commercially successful computer in 1951 under Sperry Rand.^[1]^[3] BINAC's legacy endures as a bridge between experimental academic machines like ENIAC and practical commercial computing, underscoring the challenges of transitioning stored-program concepts into reliable hardware.^[2]^[3]

Development History

Origins and Founding

The Eckert–Mauchly Computer Corporation (EMCC) was founded in 1946 by J. Presper Eckert and John Mauchly, who had previously led the ENIAC project at the University of Pennsylvania's Moore School of Electrical Engineering.^[4] After completing ENIAC in 1945, the duo left academia amid disputes over patent rights and a desire to commercialize electronic computing technology.^[5] Initially named the Electronic Control Company upon its incorporation in March 1946, it was renamed EMCC in 1947 to reflect its focus on computer development.^[6]^[7] Eckert and Mauchly were driven to create BINAC by the shortcomings of ENIAC, which relied on decimal arithmetic and lacked a stored-program architecture, requiring manual rewiring for different tasks.^[8]^[9] ENIAC's design, while groundbreaking, was inefficient for versatile applications, prompting the shift to a binary system that enabled high-speed arithmetic and internal program storage.^[10] This conceptual evolution built on ideas from the contemporaneous EDVAC report but emphasized practical implementation for real-world use.^[11] In October 1947, the Electronic Control Company secured its first major contract with Northrop Aircraft Company for $100,000 to develop BINAC specifically for guided missile trajectory calculations.^[12]^[7] The agreement provided crucial upfront funding of $80,000 but highlighted the company's precarious finances, as development costs quickly outpaced resources.^[7] Facing delays in government contracts and limited initial capital from personal investments, the Electronic Control Company pivoted toward commercial clients like Northrop to stabilize operations and fund broader ambitions, including the UNIVAC project.^[13]^[14]

Project Planning and Design

The BINAC project commenced in October 1947, when the Electronic Control Company signed a contract with Northrop Aircraft Company to design and build the computer.^[7] Development proceeded over the subsequent two years, with initial modules completed by August-September 1948, culminating in the system's operational status on August 22, 1949, prior to shipment to the customer.^[7] The contract stipulated a total value of $100,000 for the company, comprising $80,000 paid upfront and $20,000 upon delivery, though the company's actual development costs reached approximately $278,000, resulting in a financial loss.^[7] The effort engaged a dedicated team of engineers, including key figures like Albert A. Auerbach, under the leadership of J. Presper Eckert and John W. Mauchly.^[7]^[15] Central to the high-level design goals was the adoption of a fully binary architecture, chosen for its computational efficiency in electronic operations—requiring only two-state decisions (0 or 1) at each step, unlike the more complex decimal system of their prior ENIAC project—drawing directly from Eckert and Mauchly's experience with that machine. The BINAC incorporated stored-program capability, enabling instructions and data to reside in the same memory, positioning it as the first such electronic stored-program computer in the United States. Additionally, a dual-processor configuration was planned, with two independent central processing units operating in parallel to provide redundancy, facilitate self-verification of computations, and enhance overall processing speed.^[7]^[10]^[16] Among the pivotal planning decisions was the use of mercury delay-line memory, selected for its cost-effectiveness by leveraging acoustic wave propagation in mercury tubes to store data—replacing thousands of vacuum tubes otherwise needed for equivalent capacity—while maintaining reliability for the era's technology. The project targeted applications in aerospace engineering, specifically complex calculations for guided missile design and aerodynamic simulations required by Northrop.^[7]^[17]

Technical Architecture

Hardware Components

The BINAC was a bit-serial binary computer built primarily with approximately 1,400 vacuum tubes (700 per processor unit), a significant reduction from the 18,000 tubes used in its predecessor, the ENIAC.^[18] This vacuum-tube-based architecture enabled electronic switching and amplification essential for its operations. The machine incorporated a dual-processor design, featuring two independent serial processing units that operated in tandem for redundancy and error-checking, a concept carried over from the project's initial planning.^[10] It also pioneered the use of germanium diodes in logic circuits, an early step toward semiconductor-based computing.^[10] Input to the BINAC was facilitated through two primary methods: an eight-key octal keypad for manual entry of data and instructions in octal code (digits 0-7), and an 8-channel magnetic tape reader for loading larger volumes of pre-prepared data.^[19] The keypad allowed direct interaction by translating key presses into binary pulses, while the magnetic tape system supported bulk input from oxide-coated plastic tapes, marking an early adoption of this medium for computer I/O.^[10] The BINAC's internal clock rate was 4 MHz, governing the timing of its bit-serial operations.^[19] In terms of physical characteristics, the machine consumed approximately 8 kVA of power, consistent with the high energy demands of vacuum-tube technology in the late 1940s.^[20] Its design was notably compact for the era, with each processor unit measuring about 5 feet in height, 4 feet in length, and 1 foot in width, occupying two cabinets that together weighed far less than earlier computers, though it remained stationary and non-portable.^[10]

Memory and Processing

BINAC utilized two independent mercury delay-line memory stores, one associated with each central processing unit (CPU), providing a total high-speed storage capacity of 1,024 words across the system.^[19] Each store held 512 words organized into 16 channels, with each channel accommodating 32 words consisting of 31 bits; an additional 11-bit interval separated words to account for propagation delays in the acoustic medium.^[10] This mercury-based design, leveraging acoustic waves in tubes of mercury for data recirculation, enabled reliable short-term storage but required continuous refresh to maintain data integrity, with a word access time of approximately 10 microseconds determined by the delay-line circulation rate.^[21] The system's processing was handled by two identical bit-serial CPUs that operated in complete synchrony, duplicating all arithmetic, control, and memory operations to facilitate real-time fault detection and tolerance through cross-verification of results.^[19] Arithmetic computations employed a binary two's complement representation—a deliberate evolution from the decimal system used in the earlier ENIAC—processed serially bit by bit at a clock rate of 4 MHz.^[19] Basic operations included addition at 3,500 per second and multiplication at 1,000 per second, including memory access, reflecting the dominance of operand fetch times in overall instruction latency.^[19] BINAC supported stored-program execution, where both instructions and data were represented uniformly in 31-bit words, allowing flexible program storage within the same memory space as operands.^[21] The instruction set comprised binary-encoded commands, typically fitting two instructions per 31-bit word with a 5-bit operation code and a 9-bit (3-octal-digit) address field, enabling operations such as load, store, add, subtract, multiply, divide, and conditional jumps while emphasizing numeric computation over logical functions.^[21] This architecture prioritized reliability and simplicity, with the dual-processor redundancy ensuring that discrepancies between the units could trigger halts for maintenance, thereby enhancing operational dependability in early computing environments.^[19]

Testing and Deployment

Early Test Programs

The early test programs for the BINAC were conducted at the Eckert-Mauchly Computer Corporation (EMCC) laboratories in Philadelphia, prior to the system's disassembly and shipment to its customer. These internal validation efforts focused on verifying the machine's core functionality using short, targeted routines stored in its mercury delay-line memory, which consisted of 16 channels each holding 32 31-bit words (512 words total per processor).^[22]^[20] The first successful run occurred on March 7, 1949, when the BINAC executed 217 iterations of a 23-instruction program to compute squares, confirming basic arithmetic operations without error. Subsequent tests in early 1949 included programs for calculating square roots, evaluating trigonometric functions such as sine and cosine, performing multiply and divide operations, and running simple simulations. By August 1949, EMCC engineers had developed at least ten such short routines, with additional variations enabling demonstrations of floating-point decimals, reciprocals, and double-precision computations.^[7]^[22] Testing faced notable challenges, particularly in stabilizing the mercury delay-line memory against latency and signal degradation, which required adjustments to tank sizes and exploratory work on alternative electrostatic storage. Synchronization between the two central processing units also proved difficult, addressed through refinements in input-output mechanisms and block data transfers to match processing speeds. These issues were iteratively debugged during the Philadelphia trials to ensure reliable operation before public demonstrations in August 1949.^[7]^[22]

Customer Delivery and Acceptance

The BINAC was delivered to the Northrop Aircraft Company in Hawthorne, California, in September 1949, approximately 15 months behind schedule and at a cost overrun of $178,000 that Eckert-Mauchly Computer Corporation (EMCC) absorbed.^[1] The machine was disassembled in Philadelphia and shipped in crates to facilitate transport, arriving after a cross-country journey that exposed its fragile components to potential damage.^[23] Upon arrival, the crates sat under a tarp in a parking lot for six months before re-assembly began, further delaying integration into Northrop's operations.^[24] Acceptance tests focused on demonstrations of missile guidance and aerodynamic calculations, such as trajectory modeling for projects like the Snark missile, to verify the machine's utility for airborne navigation feasibility.^[1] Post-delivery, despite challenges, the BINAC demonstrated partial success by solving complex problems such as 26 iterations of Poisson's equation in 2 hours and a wind pressure computation on a rubber diaphragm in 7 minutes—a task that would have taken a mathematician a year—though full functionality was never achieved due to re-assembly challenges handled by inexperienced Northrop staff—a recent college graduate without EMCC oversight, restricted by security protocols.^[10]^[23] Post-delivery issues included widespread vacuum tube failures, with approximately 25% of the tubes deemed unsatisfactory and 75% rejected for emission problems, likely worsened by transport stresses and environmental factors like weather affecting reliability.^[1]^[24] Inadequate on-site support from EMCC exacerbated these, as technicians were denied access; the dual-processor design intended for redundancy failed to synchronize via the high-speed bus, limiting operation to one unit at a time for short bursts of about 15 minutes.^[23] The machine ran intermittently for research tasks but proved unreliable overall, operating sporadically rather than continuously.^[24] Ultimately, Northrop cannibalized parts from the two modules—such as memory from one and arithmetic units from the other—to cobble together a single functional unit, which was used until at least April 1953 but never met the contract's full expectations for missile applications.^[24] The project's operational failures highlighted early challenges in commercial computer deployment, leading EMCC to prioritize UNIVAC development over further BINAC support.^[1]

Documentation and Legacy

First User Manual

The first user manual for the BINAC was produced by the Eckert-Mauchly Computer Corporation (EMCC) in 1949, with primary authorship by Joseph D. Chapline, a technical writer who had previously assisted on the ENIAC project at the University of Pennsylvania.^[10] This document marked one of the earliest attempts to create accessible computer documentation targeted at non-expert end-users, such as engineers and operators at client organizations who lacked specialized knowledge of electronic computing systems.^[25] Chapline, often regarded as a pioneer in technical writing, composed the manual longhand over several days, drawing on his experience to produce a clear and methodical guide.^[25] Inspired by the user manuals of the automobile industry, the BINAC manual prioritized practical usability over abstract theory, presenting information in a straightforward, step-by-step format to enable effective machine operation.^[26] The approximately 38-page document covered key areas including initial setup procedures, routine operational instructions, programming methods using octal codes for input and addressing, and basic troubleshooting techniques.^[27] It provided an overview of the system's components, such as the dual central processing units and mercury delay-line memory, to help users understand and interact with the hardware without delving into design intricacies.^[10] Among its innovations, the manual featured illustrated wiring diagrams to aid in physical inspections and connections, detailed listings of error codes accompanied by diagnostic steps, and comprehensive guides for common tasks like loading programs from magnetic tape.^[10] These elements emphasized hands-on application, allowing operators to resolve issues and perform daily functions efficiently.^[25] The manual was distributed to Northrop Aircraft Corporation alongside the BINAC delivery in September 1949, serving as essential preparatory material for the client's integration and use of the system.^[26] It later influenced documentation practices at EMCC, providing a template for user guides in follow-on projects like the UNIVAC I.^[25]

Historical Significance

The BINAC, delivered in 1949, was marketed by the Eckert-Mauchly Computer Corporation as the first commercial stored-program computer in the United States, representing a pivotal step from the ENIAC's wired-program architecture toward more flexible electronic computing systems.^[10] As the only machine produced by the company before its acquisition by Remington Rand, it bridged the gap to the UNIVAC I, which debuted in 1951 and became the first widely deployed commercial computer.^[18] This transition underscored BINAC's role in validating the practical engineering of stored-program designs for non-military applications, particularly through its binary architecture that enabled instructions and data to reside interchangeably in memory.^[28] Despite its innovations, BINAC faced significant limitations that curtailed its adoption and legacy. Only a single unit was constructed, primarily for Northrop Aircraft's guided missile research, at a total development cost of approximately $278,000—far exceeding the initial $100,000 contract price—and it remained underutilized due to persistent operational failures and reliability issues reported as early as 1950.^[18]^[10] These challenges, including synchronization problems between its dual processors and the complexities of manual octal data entry, highlighted the risks of scaling early electronic computing for commercial viability without robust error-checking mechanisms.^[10] BINAC's influence extended beyond its immediate use, as its core components, including mercury delay-line memory units, were repurposed in the development and testing of the UNIVAC I, accelerating the transition to production-scale systems.^[5] It demonstrated the feasibility of binary stored-program computing in a compact form—using just 1,400 vacuum tubes compared to ENIAC's approximately 18,000—paving the way for standardized designs in subsequent machines.^[18] Additionally, BINAC advanced mercury delay-line technology, refining acoustic memory propagation techniques originally explored by J. Presper Eckert during World War II radar work, which informed storage solutions in UNIVAC and other 1950s computers.^[29] In modern historical assessments, BINAC is recognized as a symbolic milestone in the shift from experimental to commercial computing, though no complete surviving examples exist today.^[18] The Computer History Museum preserves related artifacts, such as promotional brochures and manuals, emphasizing its contributions to the Eckert-Mauchly legacy despite financial strains that nearly bankrupted the firm.^[30] Scholarly analyses, including Nancy Stern's 1979 case study, portray it as a critical, if flawed, experiment that informed the business and technical strategies leading to UNIVAC's success.^[31]

References

[1]
5.9 UNIVAC, Part I: Development | Bit by Bit
Once again, Mauchly and Eckert underestimated their costs and development schedule. Completed in August 1949, BINAC was fifteen months behind schedule and ...
[2]
A Short History of the Second American Revolution
Eckert and Mauchly also used mercury delay lines in the BINAC (1949) and UNIVAC (1951), two computers they designed and built after leaving the Moore School to ...
[3]
[PDF] History of Electronic Computers
BINAC (1950). UNIVAC (1951). (taken over by Sperry. Rand Co; for several years was undisputed leader of U.S. computer market). EDSAC (1949). M.V. Wilkes.
[4]
J. Presper Eckert | Memorial Tributes: Volume 10
The computer, which was to operate until 1955, was more than 1,000 times faster than its electromechanical contemporaries and could execute up to 5,000 ...
[5]
Making UNIVAC a Business - CHM Revolution
Having led the project that created ENIAC, they left academia in 1946, forming the Eckert-Mauchly Computer Corporation to develop UNIVAC.Missing: origins | Show results with:origins
[6]
Collection: Sperry Rand Corporation, Univac Division. Honeywell vs ...
In 1946, Eckert and Mauchly left the Moore School and formed their own commercial computer enterprise, the Electronic Control Company, which was later ...
[7]
[PDF] CHAPTER 3 - Electronics Technology - Princeton University
Eniac. No stored program capability; vacuum tube. Preparation of ballistics tables. processor. One. Early 1950's. Univac I. Stored program, but in binary ...
[8]
[PPT] Template - Carnegie Mellon University in Qatar
No Stored Program. Mechanical Dram based Regenerative. capacitor memory ... Eckert & ENIAC 1945 Decimal Electronic Plug Board Mauchly; John von IAS 1946 ...
[9]
Innovative Aspects of the BINAC, the First Electronic Computer Ever ...
Eckert and Mauchly's BINAC was the first stored-program computer ever fully operational, since the Moore School's EDVAC, which was designed to be the first ...Missing: origins | Show results with:origins
[10]
The BINAC: A Case Study in the History of Technology
The BINAC, short for Binary Automatic Computer, was developed by John Presper Eckert, Jr. and John William Mauchly during the years 1947-1949 under a contract ...
[11]
BINAC gets under way, October 9, 1947 - EDN
Oct 9, 2012 · A contract to build BINAC, the Binary Automatic Computer, was signed on October 9, 1947. The early electronic computer was designed for Northrop Aircraft ...
[12]
[PDF] The Albert A. Auerbach Collection
October 1947. Eckert & Mauchly agree to build the BINAC for Northrop. Aircraft Company. It will be the first stored-program electronic computer. 1947. Auerbach ...
[13]
The Eckert-Mauchly Computers: Conceptual Triumphs, Commercial
By the summer of 1948 Eckert and Mauchly had several substantial contracts, but their financial problems did not diminish; in fact, they became more severe ...
[14]
[PDF] The Eckert-Mauchly Company, 1945–1951 - Hal-Inria
Jul 19, 2017 · Eckert and Mauchly's uncertain financial position was a serious obstacle. Prudential was unwilling to sign a large contract with a small ...
[15]
http://www.abortretry.fail/p/the-eckert-mauchly-computer-corporation
[16]
http://palosverdes.com/lasthurrah/binac-description.html
[17]
First American computer company run by Eckert and Mauchley
Oct 26, 2024 · John W. Mauchley inventors of the ENIAC³, BINAC was their first product, UNIVAC⁴ was their second. It was the first stored-program computer in ...BINAC Computer and its Role in UNIVAC I Development - FacebookBINAC World's First Commercial Digital Computer (1949) - FacebookMore results from www.facebook.com
[18]
October 9: BINAC Computer to Be Built | This Day in History
Oct 9, 2025 · Presper Eckert and John Mauchly. The company became a division of Remington Rand Corp. before completing its next project, the UNIVAC. The first ...
[19]
[PDF] The Binac, 1949
1, This is used to read intelligence into the computer from a previously prepared magnet ie tape; such data will usually represent instruct ions to the computer.Missing: methods | Show results with:methods
[20]
[PDF] Operating and Maintenance Manual for the BINAC
The binary point shall not be shown explicitly, but arithmetic operations shall treat all numbers as though they were in the range -1 to +1. 2.2 Input and ...
[21]
binac
The idea behind BINAC was to have all operations checked by running two sections of the computer independently and comparing each step on a high speed bus.Missing: processor | Show results with:processor
[22]
None
Below is a merged summary of the BINAC development at EMCC Labs in Philadelphia in 1949, consolidating all information from the provided segments into a comprehensive response. To maximize detail and clarity, I will use a table in CSV format for key data points (e.g., development, testing, programs, challenges, etc.), followed by a narrative summary that integrates additional context, dates, and notes. This approach ensures all information is retained while maintaining readability.
[23]
Pioneer Programmer: Jean Jennings Bartik and the computer that ...
... crates, and shipped them from Philadelphia to California. Once the crates got to California, Northrop allowed the BINAC to sit in pieces for months before ...
[24]
[PDF] Computer Oral History Collection, 1969-1973, 1977
Northrop was setting up a BINAC programming group. BINAC was the first ... We would use different parts like one memory from one machine, and the ...
[25]
[PDF] Joseph D. Chapline: Technical Communication's Mozart - MST.edu
John Brockmann describes the BINAC manual as "the first computer user manual" [5, p. 40] and refers to Chapline as. "Technical Communication's Odysseus ...
[26]
The Eckert-Mauchly Computer Corporation - Abort, Retry, Fail
Feb 25, 2024 · Eckert and Mauchly's new computer company, Electronic Control Company, was founded on the 15th of March in 1946 at 1215 Walnut St. in ...Missing: origins | Show results with:origins
[27]
[BINAC] Operating and Maintenance Manual for the ... - Sotheby's
Jul 17, 2025 · Employee Joseph D. Chapline, now considered the “Father of Technical Writing,” was tasked with writing the BINAC's manual, thereby becoming the ...
[28]
First Electronic Stored-Program Computer Is Completed - EBSCO
The BINAC featured a dual-processor design that minimized errors through continual checks between the two processing units, and it utilized a novel mercury ...
[29]
Mercury delay line | computer technology - Britannica
Eckert had already built and experimented in 1943 with such a delay line (using mercury) in conjunction with radar research, and sometime in 1944 he hit upon ...Missing: BINAC advancement
[30]
The Binac: A Product of the Eckert-Mauchley Computer Corp.
The brochure is printed on plain white paper in the form of a scholarly paper discussing the Binac computer and was staped together in 3 places down the ...Missing: modern | Show results with:modern
[31]
https://ieeexplore.ieee.org/document/4392879