Hard disk drive (IBM RAMAC)

What it is

Fifty 24-inch platters storing 5 MB with random access in under a second. It inaugurated mass direct-access storage.

What it led to

• Online transactions (SABRE airline booking, banking) and databases
• The birth of Silicon Valley as a hub for storage and semiconductors
• The accumulation of data that today feeds surveillance and machine learning

Built on

• Magnetic drum memory1932
• Magnetic tape data storage (UNISERVO)1951

Made possible

• Time-sharing operating system (CTSS, Multics)1961
• Relational database model1970
• Floppy disk1971
• Solid-state drive (flash SSD)1991

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