Programmable logic controller and knife: what they have in common

1. Step 1. Programmable logic controller — has part — Microprocessor. A processor.
2. Step 2. Microprocessor — evolved from — Electronic calculator. The Intel 4004 was designed for a Busicom calculator.
3. Step 3. Electronic calculator — evolved from — Arithmometer. Electronics replaced mechanics.
4. Step 4. Arithmometer — has part — Crank. The handle for adding and subtracting.
5. Step 5. Crank — is part of — Meat grinder. A handle.
6. Step 6. Meat grinder — has part — Knife. A cross-shaped blade.

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