Memory was the largest technical problem facing the early computer industry and the first computer manufacturers tried many different approaches before solving the problem. Initial systems would store bits as sound pulses in tubes filled with mercury; as electron charges on the face of cathode ray tubes; or as magnetized regions on rotating magnetic drums.
It was the perfection of magnetic core memory in 1953 by MIT professor Jay Forrester that provided a technologically satisfactory solution to the memory problem.
Even so, computer memories remained expensive, and thus small, until the creation of integrated circuit memory devices. ICs were first used for computer memory in the mid-1970s but had to wait until large scale production problems were solved a few years later before the era of inexpensive memory systems were common.