It all started with this, now you can hold it on your lap.

ENIAC, short for Electronic Numerical Integrator and Computer, was the first large-scale, electronic, digital computer capable of being reprogrammed to solve a full range of computing problems[
Physically, ENIAC was a monster. It contained 17,468 vacuum tubes, 7,200 crystal diodes 1,500 relays 70,000 resistors 10,000 capacitors and around 5 million hand-soldered joints. It weighed 30 short tons (27 t), was roughly 8 feet (2.4 m) by 3 feet (0.9 m) by 100 feet (30 m), took up 1800 square feet (167 m2), and consumed 150 kW of power. Input was possible from an IBM card reader, while an IBM card punch was used for output. These cards could be used to produce printed output offline using an IBM accounting machine, probably the IBM 405 The computer was commissioned on May 17 1943 as Project PX and constructed at Penn's Moore School of Electrical Engineering It 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 the Aberdeen Proving Ground in 1947 There, on July 29 of that year, it was turned on and would be in continuous operation until 11:45 p.m. on October 2 1955