Later UNIVACs such as the 9000 series used plated wire memory (as described in http://www.technikum29.de/en/devices/plated-wire-storage http://www.technikum29.d

Later UNIVACs such as the 9000 series used plated wire memory (as described in http://www.technikum29.de/en/devices/plated-wire-storage http://www.technikum29.de/en/devices/plated-wire-storage). However, while plated wire memory uses magnetization (already similar to the hard disks we still use today), delay line memory exploits the finiteness of signal traveling times which is a totally different concept. Back in these days, storing data was really a challenge. We are talking about working memory here, by the way. For persistent storage, all kind of punched cards and tapes were ubiquitous and magnetic tapes were in fashion. Still today, for cheap long term archival, magnetic tapes are unbeaten!