Punched card and fuel cell: what they have in common

1. Step 1. Punched card — is used in — Harvard Mark I. The program was read from punched tape and the data from punched cards.
2. Step 2. Harvard Mark I — has part — Relay. The Mark I was electromechanical, built from relays.
3. Step 3. Relay — evolved into — Programmable logic controller. It replaced relay cabinets.
4. Step 4. Programmable logic controller — is part of — Chemical plant. Process control automation.
5. Step 5. Chemical plant — uses — Catalysis. Catalysts.
6. Step 6. Catalysis — is used in — Fuel cell. A platinum catalyst.

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