The JOHNNIAC was an early computer built by the RAND Corporation (not

Remington Rand Remington Rand was an early American business machine manufacturer, originally a typewriter manufacturer and in a later incarnation the manufacturer of the UNIVAC line of mainframe computers. Formed in 1927 following a merger, Remington Rand w ...

, maker of the contemporaneous

UNIVAC I The UNIVAC I (Universal Automatic Computer I) was the first general-purpose electronic digital computer design for business application produced in the United States. It was designed principally by J. Presper Eckert and John Mauchly, the inven ...

computer) and based on the

von Neumann architecture The von Neumann architecture — also known as the von Neumann model or Princeton architecture — is a computer architecture based on a 1945 description by John von Neumann, and by others, in the '' First Draft of a Report on the EDVAC''. T ...

that had been pioneered on the

IAS machine The IAS machine was the first electronic computer built at the Institute for Advanced Study (IAS) in Princeton, New Jersey. It is sometimes called the von Neumann machine, since the paper describing its design was edited by John von Neumann, a ...

. It was named in honor of von Neumann, short for '' John von Neumann Numerical Integrator and Automatic Computer''. JOHNNIAC is arguably the longest operational early computer, being used almost continuously from 1953 for over 13 years before finally being shut down on February 11, 1966, logging over 50,000 operating hours. After two "rescues" from the scrap heap, the machine currently resides at the Computer History Museum in

Mountain View, California Mountain View is a city in Santa Clara County, California, United States. Named for its views of the Santa Cruz Mountains, it has a population of 82,376. Mountain View was integral to the early history and growth of Silicon Valley, and is the ...

. Like the IAS machine, JOHNNIAC used 40-bit words, and included 1024 words of

Selectron tube The Selectron was an early form of digital computer memory developed by Jan A. Rajchman and his group at the Radio Corporation of America (RCA) under the direction of Vladimir K. Zworykin. It was a vacuum tube that stored digital data as elect ...

main memory, each holding 256 bits of data. Two instructions were stored in every word in 20-bit subwords consisting of an 8-bit instruction and a 12-bit address, the instructions being operated in series with the left subword running first. The initial machine had 83 instructions. A single register named ''A'' supplied an accumulator, and the machine also featured a register named ''Q'', for quotient, as well. There was only one test condition, whether or not the high bit of the A register was set. There were no

index register An index register in a computer's CPU is a processor register (or an assigned memory location) used for pointing to operand addresses during the run of a program. It is useful for stepping through strings and arrays. It can also be used for hol ...

s, and as addresses were stored in the instructions, loops had to be implemented by modifying the instructions as the program ran. Since the machine only had 10 bits of address space, two of the address bits were unused and were sometimes used for data storage by interleaving data through the instructions. JOHNNIAC weighed . Numerous modifications were made to the system over its lifetime. In March 1955, 4096 words of

magnetic-core memory Magnetic-core memory was the predominant form of random-access computer memory for 20 years between about 1955 and 1975. Such memory is often just called core memory, or, informally, core. Core memory uses toroids (rings) of a hard magneti ...

were added to the system, replacing the earlier Selectrons. This required all 12 bits of addressing, and caused programs that stored data in the "spare bits" to fail. Later in 1955 a 12k-word

drum memory Drum memory was a magnetic data storage device invented by Gustav Tauschek in 1932 in Austria. Drums were widely used in the 1950s and into the 1960s as computer memory. For many early computers, drum memory formed the main working memory of ...

secondary storage system was added as well. A

transistor upright=1.4, gate (G), body (B), source (S) and drain (D) terminals. The gate is separated from the body by an insulating layer (pink). A transistor is a semiconductor device used to Electronic amplifier, amplify or electronic switch, switch ...

-based adder replaced the original tube-based adder in 1956. Numerous changes were made to the

input/output In computing, input/output (I/O, or informally io or IO) is the communication between an information processing system, such as a computer, and the outside world, possibly a human or another information processing system. Inputs are the signals ...

peripherals as well, and in 1964, a real-time clock was added to support

time-sharing In computing, time-sharing is the sharing of a computing resource among many users at the same time by means of multiprogramming and multi-tasking.DEC Timesharing (1965), by Peter Clark, The DEC Professional, Volume 1, Number 1 Its emergence ...

. One JOHNNIAC legacy was the

JOSS Joss may refer to: * Joss (name), including a list of people with the name * JOSS, a time-sharing programming language * Joss (Chinese statue), a religious object * Joss JP1, an Australian-built supercar * Joss paper, a type of burnt offering * ...

programming language A programming language is a system of notation for writing computer programs. Most programming languages are text-based formal languages, but they may also be graphical. They are a kind of computer language. The description of a programming ...

(the ''JOHNNIAC Open Shop System''), an easy-to-use language which catered to novices. JOSS was an ancestor of DEC's FOCAL and of MUMPS. The CYCLONE at

Iowa State University Iowa State University of Science and Technology (Iowa State University, Iowa State, or ISU) is a public land-grant research university in Ames, Iowa. Founded in 1858 as the Iowa Agricultural College and Model Farm, Iowa State became one of the ...

was a direct clone of JOHNNIAC, and was instruction compatible with it (the

ILLIAC I The ILLIAC I (Illinois Automatic Computer), a pioneering computer in the ILLIAC series of computers built in 1952 by the University of Illinois, was the first computer built and owned entirely by a United States educational institution. Compute ...

may have been as well). Cyclone was later updated to include a hardware for floating-point arithmetic. File:JOHNNIAC badge.JPG, Johniac name badge on computer frame File:JOHNNIAC.JPG, Alternate Johnniac view File:JOHNNIAC buttons.JPG, Johnniac keyboard

References

External links

Johnniac
entry on ''Antique Computers'' site.
The History of the JOHNNIAC
(RAND monograph)
Oral history interview with Keith W. Uncapher

Charles Babbage Institute The IT History Society (ITHS) is an organization that supports the history and scholarship of information technology by encouraging, fostering, and facilitating archival and historical research. Formerly known as the Charles Babbage Foundation, ...

, University of Minnesota. Review of projects at RAND Corporation when

Keith Uncapher Keith Uncapher (1922–2002) was an American computer engineer and manager. At the RAND Corporation Uncapher worked on several pioneering computer projects. He founded the Information Sciences Institute (ISI) at the University of Southern Califo ...

was hired in 1950 through the early 1970s, such as JOHNNIAC,

, a survivable national network, and work related to the

ARPANET The Advanced Research Projects Agency Network (ARPANET) was the first wide-area packet-switched network with distributed control and one of the first networks to implement the TCP/IP protocol suite. Both technologies became the technical fou ...

. {{DEFAULTSORT:Johnniac IAS architecture computers Vacuum tube computers

See also

References

External links