What differentiates second and third generation of computers?

CONCEPT: Computer generations are classified by the core electronic technology used to build them: the first generation used vacuum tubes, the second generation used transistors, the third generation used integrated circuits (ICs), the fourth generation used microprocessors, and the emerging fifth generation uses AI and nanotechnology-based systems.

APPLICATION: Applying this to the second-to-third generation shift:

1. Second-generation computers (around 1955-1964) replaced the bulky, heat-generating vacuum tubes with transistors, making machines smaller, faster, and more power-efficient.

2. Third-generation computers (around 1964-1971) replaced discrete transistors with integrated circuits (ICs), which packed many transistors onto a single silicon chip.

3. So the technology shift that separates the second generation from the third generation is: transistors (used in the second generation) giving way to integrated circuits (used in the third generation).

CROSS-CHECK: Checking against the other generations confirms this and rules out the remaining options: the vacuum tube is the first-generation technology, which already predates the second generation; the microprocessor is the fourth-generation technology, which differentiates the third generation from the fourth, not the second from the third; and nanotechnology is associated with the emerging fifth generation. Only the transistor-to-integrated-circuit shift matches the boundary between the second and third generations.

Hence, the correct differentiator between second and third generation computers is transistors and integrated circuit (IC).