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Computer dictionary definition for what ENIAC (Electronic Numerical Integrator and Calculator) means including related links, information, and terms. By , the end of its operation, the ENIAC occupied about 1, square feet and Computer acronyms, CSIRAC, EDVAC, Hardware terms, UNIVAC. The First Draft of a Report on the EDVAC is an incomplete page . Eckert, a co-inventor of the ENIAC, discusses its development at the University of Pennsylvania's Moore School of Electrical Engineering;. ENIAC, short for Electronic Numerical Integrator And Computer,was the first EDVAC (Electronic Discrete Variable Automatic Computer) was one of the earliest.
This was used to see if a number was converging, for example. A loudspeaker was connected to the accumulator's sign bit; experienced users knew healthy and unhealthy sounds of programs, particularly programs 'hung' in a loop. After office hours certain "Authorised Users" were allowed to run the machine for themselves, which went on late into the night until a valve blew — which usually happened according to one such user.
EDVAC - Wikipedia
As there was no index register until much later, the only way of accessing an array was to alter which memory location a particular instruction was referencing. David Wheelerwho earned the world's first Computer Science PhD working on the project, is credited with inventing the concept of a subroutine.
Users wrote programs that called a routine by jumping to the start of the subroutine with the return address i. By convention the subroutine expected this and the first thing it did was to modify its concluding jump instruction to that return address. Multiple and nested subroutines could be called so long as the user knew the length of each one in order to calculate the location to jump to; recursive calls were forbidden. The user then copied the code for the subroutine from a master tape onto their own tape following the end of their own program.
In order to achieve its high speed, the panels had to send and receive numbers, compute, save the answer and trigger the next operation, all without any moving parts. Key to its versatility was the ability to branch; it could trigger different operations, depending on the sign of a computed result.
This section needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. July Learn how and when to remove this template message By the end of its operation inENIAC contained 20, vacuum tubescrystal diodesrelays70, resistors10, capacitors and approximately 5, hand- soldered joints.
While ENIAC had no system to store memory in its inception, these punch cards could be used for external memory storage.
Arithmetic was performed by "counting" pulses with the ring counters and generating carry pulses if the counter "wrapped around", the idea being to electronically emulate the operation of the digit wheels of a mechanical adding machine.
ENIAC had 20 ten-digit signed accumulatorswhich used ten's complement representation and could perform simple addition or subtraction operations between any of them and a source e. It was possible to connect several accumulators to run simultaneously, so the peak speed of operation was potentially much higher, due to parallel operation. Army photo  It was possible to wire the carry of one accumulator into another accumulator to perform double precision arithmetic, but the accumulator carry circuit timing prevented the wiring of three or more for even higher precision.
The other nine units in ENIAC were the initiating unit started and stopped the machinethe cycling unit used for synchronizing the other unitsthe master programmer controlled loop sequencingthe reader controlled an IBM punch-card readerthe printer controlled an IBM card punchthe constant transmitter, and three function tables.
If one of the numbers had fewer than 10 digits, the operation was faster. So a division or square root took up to cycles, or 28, microseconds—a rate of 35 per second.ENIAC: The First Computer
If the result had fewer than ten digits, it was obtained faster. Special high-reliability tubes were not available until Most of these failures, however, occurred during the warm-up and cool-down periods, when the tube heaters and cathodes were under the most thermal stress. According to an interview in with Eckert, "We had a tube fail about every two days and we could locate the problem within 15 minutes. Programming[ edit ] ENIAC could be programmed to perform complex sequences of operations, including loops, branches, and subroutines.
However, instead of the stored program computers that exist today, ENIAC was just a large collection of arithmetic machines, which originally had programs hard coded into the machines  by a combination of plugboard wiring and three portable function tables containing ten-way switches each.
Due to the complexity of mapping programs onto the machine, programs were only changed after huge numbers of tests of the current program. This was followed by a period of verification and debugging, aided by the ability to execute the program step by step. He estimates a few hundred minor cycles will suffice for storing the program. He proposes two kinds of fast memory, delay line and Iconoscope tube.
Each minor cycle is to be addressed as a unit word addressing, Sec. Instructions are to be executed sequentially, with a special instruction to switch to a different point in memory i. Binary digits in a delay line memory pass through the line and are fed back to the beginning. Accessing data in a delay line imposes a time penalty while waiting for the desired data to come around again. After analyzing these timing issues, he proposes organizing the delay line memory into delay line "organs" DLAs each storing bits, or 32 minor cycles, called a major cycle.
A memory access first selects the DLA 8 bits and then the minor cycle within the DLA 5 bitsfor a total of 13 address bits. For the Iconoscope memory, he recognizes that each scan point on the tube face is a capacitor and that a capacitor can store one bit.
Very high precision scanning will be needed and the memory will only last a short time, perhaps as little as a second, and therefore will need to be periodically recopied refreshed.
J. Presper Eckert
Orders instructions [ edit ] In Sec Order types include the basic arithmetic operations, moving minor cycles between CA and M word load and store in modern termsan order s that selects one of two numbers based on the sign of the previous operation, input and output and transferring CC to a memory location elsewhere a jump.
He determines the number of bits needed for the different order types, suggests immediate orders where the following word is the operand and discusses the desirability of leaving spare bits in the order format to allow for more addressable memory in the future, as well as other unspecified purposes. The possibility of storing more than one order in a minor cycle is discussed, with little enthusiasm for that approach.
A table of orders is provided, but no discussion of input and output instructions was included in the First Draft.