Engineering Research Associates of Minneapolis built the ERA 1101, the first commercially produced computer; the company´s first customer was the U.S. Navy. It held 1 million bits on its magnetic drum, the earliest magnetic storage devices. Drums registered information as magnetic pulses in tracks around a metal cylinder. Read/write heads both recorded and recovered the data. Drums eventually stored as many as 4,000 words and retrieved any one of them in as little as five-thousandths of a second.

CSIRAC (Council for Scientific and Industrial Research Automatic Computer)  originally known as CSIR Mk 1, was Australia's first digital computer, and the fourth stored program computer in the world. It was first to play digital music and is the only intact first-generation computer. The CSIRAC was constructed by a team led by Trevor Pearcey and Maston Beard, working in large part independently of similar efforts across Europe and the United States, and ran its first test program some time in November 1949.

The Manchester Mark I was one of the earliest electronic computers, developed at the University of Manchester from the Small-Scale Experimental Machine (SSEM) or "Baby", the world's first electronic stored-program computer. Work began in August 1948, and the first version was operational in April 1949. It was also called Manchester Automatic Digital Machine, or MADM. It is especially historically significant due to its pioneering inclusion of a kind of index register in its architecture, as well as being the platform on which Autocode was developed, one of the first "high-level" computer languages.

Development of the Mark I started after the SSEM demonstrated the utility of the stored-program approach, which dramatically improved a machine's flexibility. This approach was being looked at by other researchers, notably Alan Turing's efforts on the Pilot ACE, Cambridge University's EDSAC, and EDVAC in the US. The SSEM differed primarily in the choice of memory system, using the much faster Williams tubes instead of mercury delay lines

Maurice Wilkes assembled the EDSAC, the first practical stored-program computer, at Cambridge University. His ideas grew out of the Moore School lectures he had attended three years earlier.

For programming the EDSAC, Wilkes established a library of short programs called subroutines stored on punched paper tapes.  Specfication: Technology (vacuum tubes), Memory (1K words, 17 bits, mercury delay line), Speed (714 operations per second)

IBM´s Selective Sequence Electronic Calculator computed scientific data in public display near the company´s Manhattan headquarters. Before its decommissioning in 1952, the SSEC produced the moon-position tables used for plotting the course of the 1969 Apollo flight to the moon. Specification: Tehcnology (20,000 relays, 12,500 vacuum tube), Speed (multiplications per second), I/O (cards, punched tape), Floor space (40fts x 30fts)

ENIAC, short for Electronic Numerical Integrator And Computer,^[1][2] was the first general-purpose electronic computer. It was the first Turing-complete, digital computer capable of being reprogrammed to solve a full range of computing problems,^[3] although earlier machines had been built with some of these properties. ENIAC was designed and built to calculate artillery firing tables for the U.S. Army's Ballistic Research Laboratory.

The ENIAC held immediate importance. When it was announced in 1946 it was heralded in the press as a "Giant Brain." It boasted speeds one thousand times faster than electro-mechanical machines, a leap in computing power that since then has typically taken fifteen years rather than just three. This mathematical power, coupled with general-purpose programmability, excited scientists and industrialists. The inventors promoted the spread of these new ideas by teaching a series of lectures on computer architecture.

lThe ENIAC's design and construction were financed by the United States Army during World War II. The construction contract was signed on June 5, 1943, and work on computer was begun in secret by the University of Pennsylvania's Moore School of Electrical Engineering starting the following month under the code name "Project PX". The completed machine was unveiled on February 14, 1946 at the University of Pennsylvania, having cost almost $500,000. ENIAC was shut down on November 9, 1946 for a refurbishment and a memory upgrade, and was transferred to Aberdeen Proving Ground, Maryland in 1947. There, on July 29, 1947, it was turned on and would be in continuous operation until 11:45 p.m. on October 2, 1955.

The Colossus machines were electronic computing devices used by British codebreakers to read encrypted German messages during World War II. These were the world's first programmable, digital, electronic, computing devices. They used vacuum tubes (thermionic valves) to perform the calculations.

Colossus was designed by engineer Tommy Flowers with input from Allen Coombs, Sid Broadhurst and Bill Chandler at the Post Office Research Station, Dollis Hill to solve a problem posed by mathematician Max Newman at Bletchley Park. The prototype, Colossus Mark 1, was shown to be working in December 1943 and was operational at Bletchley Park by February 1944. An improved Colossus Mark 2 first worked on 1 June 1944, just in time for the Normandy Landings. Ten Colossi were in use by the end of the war.

The Colossus computers were used to help decipher teleprinter messages which had been encrypted using the Lorenz SZ40/42 machine — British codebreakers referred to encrypted German teleprinter traffic as "Fish" and called the SZ40/42 machine and its traffic "Tunny". Colossus compared two data streams, counting each match based on a programmable Boolean function. The encrypted message was read at high speed from a paper tape. The other stream was generated internally, and was an electronic simulation of the Lorenz machine at various trial settings. If the match count for a setting was above a certain threshold, it would be sent as output to an electric typewriter.

In spite of the destruction of the Colossus hardware and blueprints as part of the effort to maintain a project secrecy that was kept up into the 1970s—a secrecy that deprived some of the Colossus creators of credit for their pioneering advancements in electronic digital computing during their lifetimes—a functional replica of a Colossus computer was completed in 2007.

Harvard Mark-1 is completed. Conceived by Harvard professor Howard Aiken, and designed and built by IBM, the Harvard Mark-1 was a room-sized, relay-based calculator. The machine had a fifty-foot long camshaft that synchronized the machine’s thousands of component parts. The Mark-1 was used to produce mathematical tables but was soon superseded by stored program computers.

Project Whirlwind begins. During World War II, the U.S. Navy approached the Massachusetts Institute of Technology (MIT) about building a flight simulator to train bomber crews. The team first built a large analog computer, but found it inaccurate and inflexible. After designers saw a demonstration of the ENIAC computer, they decided on building a digital computer. By the time the Whirlwind was completed in 1951, the Navy had lost interest in the project, though the U.S. Air Force would eventually support the project which would influence the design of the SAGE program.

The Atanasoff-Berry Computer is completed. Built at Iowa State College (now University), the Atanasoff-Berry Computer (ABC) was designed and built by Professor John Vincent Atanasoff and graduate student Cliff Berry between 1939 and 1942. While the ABC was never fully-functional, it won a patent dispute relating to the invention of the computer when Atanasoff proved that ENIAC co-designer John Mauchly had come to see the ABC shortly after it was completed

Konrad Zuse finishes the Z3 computer. The Z3 was an early computer built by German engineer Konrad Zuse working in complete isolation from developments elsewhere. Using 2,300 relays, the Z3 used floating point binary arithmetic and had a 22-bit word length. The original Z3 was destroyed in a bombing raid of Berlin in late 1943. However, Zuse later supervised a reconstruction of the Z3 in the 1960s which is currently on display at the Deutsches Museum in Berlin.

The first Bombe is completed. Based partly on the design of the Polish “Bomba,” a mechanical means of decrypting Nazi military communications during WWII, the British Bombe design was greatly influenced by the work of computer pioneer Alan Turing and others.  Many bombes were built.  Together they dramatically improved the intelligence gathering and processing capabilities of Allied forces. [Computers]

The Complex Number Calculator (CNC) is completed. In 1939, Bell Telephone Laboratories completed this calculator, designed by researcher George Stibitz.  In 1940, Stibitz demonstrated the CNC at an American Mathematical Society conference held at Dartmouth College.  Stibitz stunned the group by performing calculations remotely on the CNC (located in New York City) using a Teletype connected via special telephone lines. This is considered to be the first demonstration of remote access computing.

Hewlett-Packard is Founded. David Packard and Bill Hewlett found Hewlett-Packard in a Palo Alto, California garage. Their first product was the HP 200A Audio Oscillator, which rapidly becomes a popular piece of test equipment for engineers. Walt Disney Pictures ordered eight of the 200B model to use as sound effects generators for the 1940 movie “Fantasia.”

The Atanasoff–Berry Computer (ABC) was the first electronic digital computing device. Conceived in 1937, the machine was not programmable, being designed only to solve systems of linear equations. It was successfully tested in 1942. However, its intermediate result storage mechanism, a paper card writer/reader, was unreliable, and when Atanasoff left Iowa State University for World War II assignments, work on the machine was discontinued. The ABC pioneered important elements of modern computing, including binary arithmetic and electronic switching elements, but its special-purpose nature and lack of a changeable, stored program distinguish it from modern computers.

John Vincent Atanasoff's and Clifford Berry's computer work was not widely known until it was rediscovered in the 1960s, amidst conflicting claims about the first instance of an electronic computer. The ENIAC computer was considered to be the first computer in the modern sense, but in 1973 a U.S. District Court invalidated the ENIAC patent and concluded that the ABC was the first "computer"