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zk/Magnetic_tape.md

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+---
+title: Magnetic_tape
+tags: [computer-history, storage]
+created: Monday, September 23, 2024
+---
+
+# Magnetic tape
+
+Used for data storage in early digital computers (broadly from the
+[UNIVAC](./The_History_of_Computing_Swade.md)) 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](../img/magnetic-tape-ibm.jpeg)
+
+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](../img/magnetic-tape-disk.jpeg)
+
+It developed from open-reel tapes to cartridges and cassettes. It was superseded
+by hard disk drives and solid state drives.