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Encyclopedia > EDSAC

EDSAC (Electronic Delay Storage Automatic Calculator) was an early British computer (one of the first computers to be created). The machine, having been inspired by John von Neumann's seminal EDVAC report, was constructed by Maurice Wilkes and his team at the University of Cambridge Mathematical Laboratory in England. Image File history File links EDSAC_(10). ... Image File history File links EDSAC_(10). ... A drawing of a desktop computer. ... John von Neumann in the 1940s. ... The EDVAC as installed in Building 328 at the Ballistics Research Laboratory. ... Maurice V. Wilkes Maurice Vincent Wilkes (born June 26, 1913 in Dudley, Staffordshire, England) is a British computer scientist, credited with several important developments in computing. ... The University of Cambridge is the second-oldest university in the English-speaking world, with one of the most selective sets of entry requirements in the United Kingdom. ... The Computer Laboratory is Cambridge Universitys computer science department. ... Royal motto (French): Dieu et mon droit (Translated: God and my right) Englands location within the UK Official language English de facto Capital London de facto Largest city London Area – Total Ranked 1st UK 130,395 km² Population – Total (mid-2004) – Total (2001 Census) – Density Ranked 1st UK 50. ...

EDSAC was the world's first practical stored program electronic computer, although not the first stored program computer (that honor goes to the Small-Scale Experimental Machine). The so-called von Neumann architecture is a model for a computing machine that uses a single storage structure to hold both the set of instructions on how to perform the computation and the data required or generated by the computation. ... Replica of the SSEM The Manchester Small-Scale Experimental Machine (SSEM), nicknamed Baby, was the first stored-program computer to run a program, on June 21, 1948. ...

The project was supported by J. Lyons & Co. Ltd., a British firm, who were rewarded with the first commercially applied computer, LEO I, based on the EDSAC design. EDSAC ran its first programs on May 6, 1949, calculating a table of squares[1] and a list of prime numbers. Pope Leo I Emperor Leo I LEO I, a computer Leo I (dwarf galaxy) which is a galaxy that orbits the Milky Way Galaxy. ... May 6 is the 126th day of the year in the Gregorian Calendar (127th in leap years). ... 1949 (MCMXLIX) is a common year starting on Saturday. ...


Technical overview

Physical components

As soon as EDSAC was constructed, it immediately began serving the University's research needs. None of its components were experimental. It used mercury delay lines for memory, and derated vacuum tubes for logic. Input was via 5-hole punched tape and output was via a teleprinter. Delay line memory was a form of computer memory used on some of the earliest digital computers, such as the EDSAC and UNIVAC I. The first such systems consisted of a column of mercury with piezo crystal transducers (a combination of speaker and microphone) at either end. ... In electronics, a vacuum tube (U.S. and Canadian English) or (thermionic) valve (outside North America) is a device generally used to amplify, or otherwise modify, a signal by controlling the movement of electrons in an evacuated space. ... A roll of punched tape Punched tape is an old-fashioned form of data storage, consisting of a long strip of paper in which holes are punched to store data. ... Teletype machines in World War II A teleprinter (teletypewriter, teletype or TTY) is a now largely obsolete electro-mechanical typewriter which can be used to communicate typed messages from point to point through a simple electrical communications channel, often just a pair of wires. ...

Initially registers were limited to an accumulator and a multiplier register. In 1953, David Wheeler, returning from a stay at the University of Illinois, designed an index register as an extension to the original EDSAC hardware. In a CPU, an accumulator is a register in which intermediate results are stored. ... David John Wheeler (9 February 1927–13 December 2004) was a computer scientist. ... The University of Illinois is the set of three public universities in Illinois. ... An index register in a computer CPU is a processor register used for modifying operand addresses during the run of a program, typically for doing vector/array operations. ...

Memory and instructions

The EDSAC's memory consisted of 1024 locations, though only 512 locations were initially implemented. Each contained 18 bits, but the first bit was unavailable due to timing restrictions, so only 17 bits were used. An instruction consisted of a five-bit instruction code (designed to be represented by a mnemonic letter, so that the Add instruction, for example, used the bit pattern for the letter A), eleven bits for a memory address (although with 1024 words, only 10 bits were needed), and one bit (for certain instruction) to control whether the instruction operated on a number contained in one word or two.

Internally, the EDSAC used twos complement, binary numbers. These were either 17-bit (one word) or 35-bit (two words) long. Unusually, the multiplier was designed to treat numbers as fixed-point fractions in the range -1 ≤ x < 1, ie the binary point was immediately to the right of the sign. The accumulator could hold 71-bits, including the sign, allowing two long (35-bit) numbers to be multiplied without losing any precision. Twos complement is a method of signifying negative numbers in binary. ... Look up binary in Wiktionary, the free dictionary. ... In digital design, a multiplier or multiplication ALU is a hardware circuit dedicated to multiplying two binary values. ... In mathematics, a fixed point of a function f is an argument x such that f(x) = x; see fixed point (mathematics). ... In a CPU, an accumulator is a register in which intermediate results are stored. ...

The instructions available were: add, subtract, multiply, collate[2], shift left, shift right, load multiplier register, store (and optionally clear) accumulator, conditional skip, read input tape, print character, round accumulator, no-op and stop. There was no division instruction (though a number of division subroutines were available) and no way to directly load a number into the accumulator (a "store and zero accumulator" instruction followed by an "add" instruction were necessary for this).

System software

The initial orders were hard-wired on a set of uniselector switches and loaded into the low words of memory at startup. By September 1949, the initial orders had reached their final form and provided a primitive relocating assembler taking advantage of the mnemonic design described above, all in 41 words. In electrical controls, a stepping switch (also called a uniselector) is an electromechanical device which allows an input connection to be connected to one of a number of possible output connections, under the control of a series of electrical pulses. ... 1949 (MCMXLIX) is a common year starting on Saturday. ... An assembler is a computer program for translating assembly language — essentially, a mnemonic representation of machine language — into object code. ...

Application software

An unusual feature of EDSAC was the availability of a substantial subroutine library. By 1951, 87 subroutines in the following categories were available for general use: floating point arithmetic; arithmetic operations on complex numbers; checking; division; exponentiation; routines relating to functions; differential equations; special functions; power series; logarithms; miscellaneous; print and layout; quadrature; read (input); nth root; Trigonometric functions; counting operations (simulating "repeat", "while" and "for" loops); vectors and matrices. :-* 1951 (MCMLI) was a common year starting on Monday; see its calendar. ... A floating-point number is a digital representation for a number in a certain subset of the rational numbers, and is often used to approximate an arbitrary real number on a computer. ... The complex numbers are an extension of the real numbers, in which all non-constant polynomials have roots. ... In mathematics, exponentiation is a process generalized from repeated (or iterated) multiplication, in much the same way that multiplication is a process generalized from repeated addition. ... In mathematics, a differential equation is an equation in which the derivatives of a function appear as variables. ... In mathematics, a power series (in one variable) is an infinite series of the form where the coefficients an, the center c, and the argument x are usually real or complex numbers. ... In mathematics, if two variables of bn = x are known, the third can be found. ... In numerical analysis, the term numerical integration is used to describe a broad family of algorithms for calculating the numerical value of a definite integral, and by extension, the term is also sometimes used to describe numerical algorithms for solving differential equations. ... In mathematics, the trigonometric functions are functions of an angle, important when studying triangles and modeling periodic phenomena. ... The word vector means carrier in Latin; it is derived from the Latin verb vehere, which means to carry. ... The word matrix (plural matrices) has several meanings. ...

Applications of EDSAC

  • In 1951, Miller and Wheeler used the machine to discover a 79-digit prime—the largest known at the time.
  • In 1952 A.S. Douglas developed OXO, a version of noughts and crosses (tic-tac-toe) for the EDSAC, with graphical output to a cathode ray tube. This may well have been the world's first computer/video game.
  • In the 1960s EDSAC was used to gather numerical evidence about solutions to elliptic curves, which led to the Birch and Swinnerton-Dyer conjecture.

OXO (or Noughts and Crosses) is a tic-tac-toe computer game made for the EDSAC computer in 1952. ... In chemistry, oxo is the formal IUPAC nomenclature for a ketone functional group. ... Tic-tac-toe, also called noughts and crosses and many other names, is a paper and pencil game between two players, O and X, who alternate in marking the spaces in a 3×3 board. ... Cathode ray tube employing electromagnetic focus and deflection Cutaway rendering of a color CRT The cathode ray tube or CRT, invented by Karl Ferdinand Braun, is the display device that was traditionally used in most computer displays, video monitors, televisions and oscilloscopes. ... For the list, see list of computer and video games. ... In mathematics, an elliptic curve is a plane curve defined by an equation of the form y2 = x3 + a x + b, which is non-singular; that is, its graph has no cusps or self-intersections. ... In mathematics, the Birch and Swinnerton-Dyer conjecture relates the rank of the abelian group of points over a number field of an elliptic curve E to the order of zero of the associated L-function L(E, s) at s = 1. ...

Further developments

EDSAC's successor, EDSAC 2, was commissioned in 1958. In 1961 an EDSAC 2 version of Autocode, an Algol-like high-level programming language for scientists and engineers, was developed by D. F. Hartley. Autocode is a class of simple high-level programming languages devised for a series of machines at the Universities of Manchester and Cambridge. ... ALGOL (short for ALGOrithmic Language) is a family of imperative computer programming languages originally developed in the mid 1950s which became the de facto standard way to report algorithms in print for almost the next 30 years. ...

In the mid-60s, a successor to the EDSAC 2 was planned, but the move was instead made to the Titan, a prototype Atlas 2—the latter having been developed from the Atlas Computer of the University of Manchester, Ferranti, and Plessey. The Titan computer was the name given to the Atlas 2 developed by Ferranti and the University of Cambridge Mathematical Laboratory. ... The Atlas Computer of the University of Manchester became operational in 1962, having been a joint development between the University, Ferranti and Plessey. ... The Victoria University of Manchester (almost always referred to as simply the University of Manchester) was a university in Manchester in England. ... Ferranti or Ferranti International Signal plc by the time of its collapse, was a major UK electrical engineering and equipment firm, known primarily for their defense electronics and power grid systems. ... The Plessey Company plc was a British-based international electronics, defence and telecommunications company. ...


  1. ^  To be precise, EDSAC's first program printed a list of the squares of the integers from 0 to 99 inclusive.
  2. ^  This instruction added the bitwise AND of the specified memory word and the multiplier register to the accumulator.

In square numbers, a square number, sometimes also called a perfect square, is an integer that can be written as the square of some other integer. ... In computer science, the term integer is used to refer to any data type which can represent some subset of the mathematical integers. ... In computer programming, a bitwise operation operates on one or two bit patterns or binary numerals at the level of their individual bits. ...

External links

Wikimedia Commons has media related to:
  • An EDSAC simulator – Developed by Martin Campbell-Kelly, Department of Computer Science, University of Warwick , England
  • 50th Anniversary of EDSAC – Dedicated website at the University of Cambridge Computer Laboratory

Image File history File links Commons-logo. ... The Wikimedia Commons (also called Commons or Wikicommons) is a repository of free content images, sound and other multimedia files. ...


  Results from FactBites:
EDSAC - Wikipedia, the free encyclopedia (700 words)
EDSAC was the world's first practical stored program electronic computer, although not the first stored program computer (that honor goes to the Small-Scale Experimental Machine).
In the 1960s EDSAC was used to gather numerical evidence about solutions to elliptic curves, which led to the Birch and Swinnerton-Dyer conjecture.
In the mid-60s, a successor to the EDSAC 2 was planned, but the move was instead made to the Titan, a prototype Atlas 2—the latter having been developed from the Atlas Computer of the University of Manchester, Ferranti, and Plessey.
  More results at FactBites »



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