What things have been used for storing computer data?

Answer 1

In the early days of computers efficient, fast, and reliable mechanisms for storing data were basically unknown and mostly had to be invented from scratch.

Ideally the memory should involve a minimum of electronics, permit random access anywhere in the same period of time, and require little maintenance to prevent data corruption in operation at a relatively low cost per memory location. However given the state of electronics at the time, there were many aspects of these requirements that conflicted.

Sequentially accessed memories are much simpler, reliable, and lower cost than randomly accessed memories but access time is variable and usually longer than randomly accessed memories. Therefore many early computers used various types of sequentially accessed memory: rotating capacitor drum dynamic memory, Mercury tank acoustic wave delay line dynamic memory, rotating multiple fixed head magnetic drum memory, rotating multiple fixed head single platter magnetic disk memory, magnetostrictive delay line dynamic memory, etc.

The early randomly accessed memories were all based on vacuum tubes: Williams-Kilburn tube (CRT) dynamic memory, various type of "flood gun" CRT static memories, Selectron tube static memory, etc. However these systems either had high maintenance costs or manufacturing the special vacuum tubes (e.g. Selectron tubes) proved impractical.

The first truly practical randomly accessed memory system developed used ferrite magnetic cores. This was not only static but also nonvolatile memory, thus offering significant advantages over earlier memories. Ferrite magnetic core memories rapidly replaced all earlier computer memory systems (except in the very lowest cost systems where very low cost sequentially accessed memories continued in use), and dominated the computer main memory and buffer memory markets for over 20 years.

Intel developed the semiconductor DRAM (i.e. the 1103) in 1970, a randomly accessed solid state dynamic memory chip. By about 1975 various semiconductor DRAM chips had replaced all earlier computer main memory types. The cost per bit was very low and has continued to drop, while memory sizes have essentially grown exponentially over time.

In terms of bulk storage (often offline, requiring operator action to make it available to the computer), many early computers used decks of punchcards or rolls of punched paper tape, but these were slow and the paper could wear out over time becoming unreadable.

Magnetic tape was introduced on the UNIVAC i (i.e. nickel plated bronze strip) in 1951 and IBM 701 (i.e. iron oxide coated cellulose acetate strip) in 1952 which was much faster, higher data capacity, and more reliable than the punchcard or paper tape storage.

IBM introduced the first movable head magnetic hard disk (i.e. the IBM 350) in 1956, this has gone through many improvements since then and in various forms now dominates most of bulk data storage market.

Photostore optical memory was the first bulk storage with a capacity exceeding one billion bits, however it involved large complex high maintenance mechanical systems to write and read the small film cards the data was recorded on.

Digital CDs and DVDs have been used for ROM for several years, but writable ones are also available.

Semiconductor Flash memories were introduced in the 1990s and although originally only used as electronically reprogrammable ROM, improved versions are now beginning to replace magnetic hard disks.

There are also many other things that have been tried as memories over time, with varying degrees of success (and frequently failure), but listing all of these would be far beyond the scope of this site and would involve writing several books. Many of them are "minor" variants on systems mentioned above.