The first generation computers used which electronic devices for building…

Concept: Computers are grouped into "generations" based on the primary active electronic component used to build their processing and switching circuitry. Each major change in that component technology marks the start of a new generation — vacuum tubes for the First Generation, transistors for the Second Generation, integrated circuit (IC) chips for the Third Generation, and microprocessors/VLSI chips from the Fourth Generation onward.

Application: The earliest computers (such as ENIAC and UNIVAC-I) built their amplifying and switching circuits using vacuum tubes — thermionic valves that control the flow of electrons through an evacuated glass envelope to switch and amplify electronic signals. Vacuum tubes were the only mature amplifying/switching device available at the time; the transistor was invented only in 1947 and did not become a manufacturable, reliable building block for computer circuitry until the mid-1950s. So the electronic device that built First Generation computer circuitry was the vacuum tube.

Cross-check / Contrast:

• Transistors are solid-state semiconductor switches that replaced vacuum tubes; they define the Second Generation of computers, not the First.

• Integrated Circuit (IC) chips pack many transistors onto a single silicon chip; they define the Third Generation of computers.

• Transducers convert one form of energy into another (for example, sound into an electrical signal); they are used in sensors and input/output devices, not as the switching/amplifying building block of processing circuitry, and are not tied to any computer generation.

Result: Hence, First Generation computers used Vacuum Tubes to build their circuitry.