Chemical plant and gutenberg printing press: what they have in common

1. Step 1. Chemical plant — has part — Programmable logic controller. Process control automation.
2. Step 2. Programmable logic controller — evolved from — Relay. It replaced relay cabinets.
3. Step 3. Relay — is part of — Harvard Mark I. The Mark I was electromechanical, built from relays.
4. Step 4. Harvard Mark I — was inspired by — Babbage’s Analytical Engine. Howard Aiken named Babbage’s work as the source of his idea.
5. Step 5. Babbage’s Analytical Engine — was inspired by — Jacquard loom. Babbage borrowed Jacquard’s punched cards directly for entering operations and data; Ada Lovelace compared the machine to the Jacquard loom.
6. Step 6. Jacquard loom — works like — Gutenberg printing press. An analogy, not proven influence: both set type and a chain of punched cards are a replaceable pattern that a machine reproduces over and over.

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