Magnetic tape

Used for data storage in early digital computers (broadly from the UNIVAC) era until the mini-computer era.

While the UNIVAC was not the first to use magnetic tape, it popularised the method due to its success and high profile.

Magnetic tape reader in IBM computer

It worked as follows. The tape was a long, narrow strip of plastic coated with a magnetic material. Data is recorded on the the tape by magnetising tiny particles on its surface. It was first used in the 1920s for audio recording.

Data is accessed in a linear, sequential manner. To reach a specific piece of data, you often need to wind through all the preceding data

It was used for long term storage rather than RAM memory due to its sequential nature. It stored data and program instructions that would be read into the machine’s memory. Data was also written out to magenetic tape, in order to store and further process results.

It could store more data than punched cards and its sequential nature accommodated batch processing well. However its sequential nature meant it was slow at retreiving specific pieces of data as it would have to cycle through all the values stored on the tape.

Magnetic tape stored as casette

It developed from open-reel tapes to cartridges and cassettes. It was superseded by hard disk drives and solid state drives.