John Vincent Atanasoff, a professor of Physics at Iowa State University conceived the first digital all-electronic computing device during his researches to solve linear equations, which comprises simultaneously an electronic circuit including a scanning mechanical memory using capacitors. Originally the memory of the computing device consists of a set of drums provided with electrical contacts displayed as

Fig 355 - The ABC computer. Replica of the first computing device invented by Dr. Astanasoff, displayin the rack provided with valves responsible by the machine operation. Courtesy: Iowa State University - USA	Fig. 355A - The computing device side view. Courtesy: Iowa State University - USA
Fig. 355B - Dr. Astnasoff’s associate, Cliff Berry operating the first all-electronic computing device. Courtesy: Iowa State University - USA Fig. 355C - Exploit view of the first all-electronic device developed by the physicist John Vincent Atanasoff working at Iowa State University – USA. Courtesy: Iowa State University - USA

small brass pins, which were connected with paper capacitors whose loading operation was monitored and adjusted by an electrical circuit. The arithmetic and logic functions were fully electronic operated by using 255 double triode valves. Fig 355
In the beginning of WWII the electromechanical computers availables were the ones such as the ASCC – Automatic Sequence Controlled Calculator – developed by IBM in the USA. They were not so fast to solve the complex ballistic calculus required by the new weapons used in the air warefare.
In this way considering the computing device developed by Atanasoff was an all-electronic concept, no longer depending of the former flip flop circuit it can be considered as the forerunner machine to use the thermionic valve in the inceptive computing science.
Thus in June 5, 1943, the American government signed a contract with the University of Pennsylvania to develop the ENIAC project, or Electronic Numerical Integrator and Computer. Three years later, the era of digital computer was ushered in with the dedication of ENIAC. Accounts of the day are reminders of how awesome the new computer was. It uses circa 18.000 thermionics valves and its U-shaped framework weighted 30 tons, occupying a 250-m2 room, and consumes around 150 kW of power.
Operating with a basic clocl rate of 100 kHz, it oculd perform additons in 0,2 us, while multiplication took about 2.8 us respectively.

Fig. 355.d – Dr. John Vincent Atanasoff inventor of the first all-electronic computing device originally developed for processing complex linear equations. Courtesy: Iowa State University - USA

Instead of binary notation, ENIAC used decimal notation and could handle up to 10 decimal digits with decade counters functioning as accumulators, which stored the numbers in the machine.
ENIAC’s first practical chore was to perform calculation problems for the famous and top-secret Manhatan project, responsible to develop the first atomic bomb in 1945.
But in spite of its advanced technology, the ENIAC had drawbacks. Since a patch board of wiring controlled it, the changing of a program was a cumbersome too slow operation.
In this way in order to improve the processing speed it would be mandatory it could store the program electronically in the same way the machine stored the data. Fig. 356
In the early days of the computer engineering,

Fig 357 – Close up of the valve 7AK7. This medial transconductance sharp-cutoff pentode provided with two control grids to be used with locktal socket was the first valve developed for digital application. It was designed in the research laboratories of Sylvania Company in the USA, circa 1948, to meet the requirements of the computing system as know as “Whirlwind Project”. Ludwell Sibley collection, KB2EVN, USA.

memory controlled the architecture design in such way the only electronic memory element available for data being processed was the expensive technique known as the flip-flop valve circuit.
By a continously improvement in the computing sciences, in 1946, the University of Pennsilvania”Moore School of Electrical Engineering, started the development for a new type of computer as known as “EDVAC” – Electronic Discrete Variable Computer -. It used a new data storage system technology now available as the mercury delay line, as a result of radar research associated with the war.
In the reality de designer noted that if the signals propagated or delayed, through the mercury were amplified and recirculated, the information could be held in the line indefinitely and could be accessed each time it came around.
Furthermore Europe was already involved in electronic digital calculator. In 1943, pressed by the war effort the Bristish developed the “Colossus”, a 1.500-valve cryptanalysis machine. The specialized “Colossus” was the British beachhead moving to coordinating its developments by establishing the National Mathematical Laboratory in 1945 where it were developed The “Williams Tube” considered as the first all-electronic memory as well as the new computing sytem – EDSAC – Electronic Delay Storage Automatic Computer – In the later forties it was launched in the market the first valve operational DC amplifier. This high-gain, low drift circuit ushered in the era of the fully electronic analog computer.
Therefore in spite of the great innovation in the thermionic science as the time being the available valves were originally devoted for radio receivers manufacturing only, and in this way they did not match the performance required to operate in the logical circuit of the first computers.
New researches led companies like Sylvania in the USA to develop the first family of pentode valves specifically to behave as an element of digital logic, as for instance the type 7AK7. Fig 357
As aforementioned from 1940 to 1950 it was a period of feverish activity in computer research and development, which certainly contributed so much to the improvements in the new generation of computers. Fig. 358

Fig. 356 – The computing device as known as ENIAC.	Fig 358 – The computing system developed by General Electric Company circa 1950. Unlike some other types of computers, the OMIBAC –Ordinal Memory Inspecting Binary Automatic Calculator – uses the binary system of counting. It is a simplified system, which employs two digits only, 1 and 0, rather than the more familiar 10- characters of the decimal one. Radio Electronics.