Unix and optical telegraph: what they have in common

1. Step 1. Unix — evolved from — Time-sharing. It grew out of Multics.
2. Step 2. Time-sharing — uses — Mainframe. Multi-user mainframes.
3. Step 3. Mainframe — has part — Magnetic-core memory. Magnetic-core memory.
4. Step 4. Magnetic-core memory — has part — Copper wire. Wires threaded through them.
5. Step 5. Copper wire — is part of — Electrical telegraph. Communication lines.
6. Step 6. Electrical telegraph — evolved from — Optical telegraph. The electrical telegraph replaced semaphore lines.

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