Electronic Delay Storage Automatic Calculator
Electronic Delay Storage Automatic Calculator (EDSAC)
The Electronic Delay Storage Automatic Calculator (EDSAC) was a pioneering computer built in the late 1940s at the University of Cambridge under the direction of Maurice Wilkes. EDSAC holds the distinction of being one of the first computers to implement the concept of a stored-program, a revolutionary step in the evolution of computing.
Background and Development
The development of EDSAC was heavily influenced by the First Draft of a Report on the EDVAC by John von Neumann, a document that expounded the architecture for storing program instructions within a computer's memory. This concept, known today as the von Neumann architecture, became foundational in computer design.
Construction of EDSAC began in 1947, with its first successful run on May 6, 1949, when it executed programs to calculate a table of square numbers and a list of prime numbers. EDSAC used mercury delay lines for memory, a technology that allowed data to be stored temporarily by converting it into sound waves traveling through a column of mercury.
Technical Specifications
EDSAC was designed as a serial computer, which means it processed one bit at a time. It had approximately 3,000 vacuum tubes and used a mercury delay line for memory storage, which was able to store up to 512 words. The machine also featured an early form of an assembler known as "initial orders," which simplified the task of programming.
The machine was built using thermionic valves (vacuum tubes), and its operations were controlled by several registers, including an accumulator, a multiplier register, and other control registers. The machine operated at a clock speed of approximately 650 cycles per second.
Influence and Legacy
EDSAC was not only a significant technological achievement but also laid the groundwork for subsequent commercial and scientific computing developments. The LEO I computer, developed by the British catering company J. Lyons & Co., was directly based on the EDSAC design, marking the first use of a computer for commercial business applications.
Moreover, EDSAC inspired the creation of EDSAC 2, which became operational in 1958. EDSAC 2 introduced the concept of microprogramming, a technique later used extensively in computer design.
Its influence also extended to programming, as Wilkes, David Wheeler, and Stanley Gill published a seminal book, "The Preparation of Programs for an Electronic Digital Computer," in 1951. This work laid the foundation for programming practices and was an early guide to programming EDSAC.