EDSAC

The EDSAC replica built by the Computer Conservation Society, photographed in 2018 while still under construction, its tall racks of tubes mirroring the Cambridge original. The Baby proved a stored program could run; EDSAC, completed at the University of Cambridge in 1949, put the idea to daily use. It was the first practical stored-program computer to offer a regular computing service to other researchers, and its users built up a library of reusable subroutines, an early form of the software libraries programmers lean on now.