Drawbridge and electronic calculator: what they have in common

1. Step 1. Drawbridge — has part — Windlass. Raised with a windlass.
2. Step 2. Windlass — uses — Crank. The handle of a windlass is a crank.
3. Step 3. Crank — is part of — Arithmometer. The handle for adding and subtracting.
4. Step 4. Arithmometer — evolved into — Electronic calculator. Electronics replaced mechanics.

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