1931: At the Massachusetts Institute of Technology (MIT), Vannevar Bush invents and builds the Differential Analyzer, the first large-scale automatic general-purpose mechanical analog computer, according to Stanford University(opens in new tab). 


1936: Alan Turing, a British scientist and mathematician, presents the principle of a universal machine, later called the Turing machine, in a paper called "On Computable Numbers…" according to Chris Bernhardt's book "Turing's Vision(opens in new tab)" (The MIT Press, 2017). Turing machines are capable of computing anything that is computable. The central concept of the modern computer is based on his ideas. Turing is later involved in the development of the Turing-Welchman Bombe, an electro-mechanical device designed to decipher Nazi codes during World War II, according to the UK's National Museum of Computing(opens in new tab). 


1937: John Vincent Atanasoff, a professor of physics and mathematics at Iowa State University, submits a grant proposal to build the first electric-only computer, without using gears, cams, belts or shafts.


1939: David Packard and Bill Hewlett found the Hewlett Packard Company in Palo Alto, California. The pair decide the name of their new company by the toss of a coin, and Hewlett-Packard's first headquarters are in Packard's garage, according to MIT. 



1941: German inventor and engineer Konrad Zuse completes his Z3 machine, the world's earliest digital computer, according to Gerard O'Regan's book "A Brief History of Computing(opens in new tab)" (Springer, 2021). The machine was destroyed during a bombing raid on Berlin during World War II. Zuse fled the German capital after the defeat of Nazi Germany and later released the world's first commercial digital computer, the Z4, in 1950, according to O'Regan. 


1941: Atanasoff and his graduate student, Clifford Berry, design the first digital electronic computer in the U.S., called the Atanasoff-Berry Computer (ABC). This marks the first time a computer is able to store information on its main memory, and is capable of performing one operation every 15 seconds, according to the book "Birthing the Computer(opens in new tab)" (Cambridge Scholars Publishing, 2016)


1945: Two professors at the University of Pennsylvania, John Mauchly and J. Presper Eckert, design and build the Electronic Numerical Integrator and Calculator (ENIAC). The machine is the first "automatic, general-purpose, electronic, decimal, digital computer," according to Edwin D. Reilly's book "Milestones in Computer Science and Information Technology" (Greenwood Press, 2003). 



1946: Mauchly and Presper leave the University of Pennsylvania and receive funding from the Census Bureau to build the UNIVAC, the first commercial computer for business and government applications.


1947: William Shockley, John Bardeen and Walter Brattain of Bell Laboratories invent the transistor. They discover how to make an electric switch with solid materials and without the need for a vacuum.


1949: A team at the University of Cambridge develops the Electronic Delay Storage Automatic Calculator (EDSAC), "the first practical stored-program computer," according to O'Regan. "EDSAC ran its first program in May 1949 when it calculated a table of squares and a list of prime numbers," O'Regan wrote. In November 1949, scientists with the Council of Scientific and Industrial Research (CSIR), now called CSIRO, build Australia's first digital computer called the Council for Scientific and Industrial Research Automatic Computer (CSIRAC). CSIRAC is the first digital computer in the world to play music, according to O'Regan.