Radar and hollerith tabulator: what they have in common

1. Step 1. Radar — has part — Magnetron. The cavity magnetron made compact radar possible.
2. Step 2. Magnetron — is a kind of — Vacuum tube. An electron vacuum device.
3. Step 3. Vacuum tube — is part of — ENIAC. ENIAC contained about 18,000 vacuum tubes.
4. Step 4. ENIAC — uses — Punched card. ENIAC’s input and output went through IBM punched-card equipment.
5. Step 5. Punched card — is used in — Hollerith tabulator. The 1890 census data was encoded on punched cards.

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