 The UNIVAC II was an improvement to the UNIVAC I that UNIVAC first delivered in 1958.The improvements included magnetic (non-mercury) core memory of 2000 to 10000 words, UNISERVO II tape drives which could use either the old UNIVAC I metal tapes or the new PET film tapes, and some circuits that were transistorized (although it was still a vacuum tube computer).It was fully compatible with existing UNIVAC I programs for both code and data.