Image:EDSAC_(10).jpg '''EDSAC''' ''('''E'''lectronic '''D'''elay '''S'''torage '''A'''utomatic '''C'''alculator)'' 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 Professor Sir Maurice_Wilkes and his team at the University_of_Cambridge Mathematical Laboratory in England. 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 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 squaresTo be precise, EDSAC's first program printed a list of the squares of the integers from 0 to 99 inclusive. and a list of prime numbers. ==Technical overview== ===Physical components=== As soon as EDSAC was constructed, it 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. 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. ===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. The instructions available were: add, subtract, multiply, collateThis instruction added the Bitwise_AND of the specified memory word and the multiplier register to the accumulator., 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. ===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); ''n''th root; Trigonometric_functions; counting operations (simulating "repeat", "while" and "for" loops); vectors and matrices. ==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. ==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. 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. ==Notes== ==External links== {{commonscat|EDSAC}} *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 ==References== * ''The Preparation of Programs for an Electronic Digital Computer'' by Professor Sir Maurice_Wilkes, David_Wheeler and Stanley_Gill, Addison-Wesley, Edition 1, 1951 Category:Early_computers Category:One-of-a-kind_computers De:Electronic_Delay_Storage_Automatic_Calculator Es:EDSAC Fr:EDSAC He:EDSAC Ja:EDSAC Pl:EDSAC Ru:EDSAC Sv:EDSAC