 A second generation of computers, through the late 1950s and 1960s featured circuit boards filled with individual transistors and magnetic core memory.These machines remained the mainstream design into the late 1960s, when integrated circuits started appearing and led to the third generation computer.The University of Manchester's experimental Transistor Computer was first operational in November 1953 and it is widely believed to be the first transistor computer to come into operation anywhere in the world.