What generation of computer is characterized by the use of vacuum tubes for circuitry and magnetic drums for main memory?

Computer generations are classified according to the core hardware technology used for processing and memory. The earliest generation, spanning roughly from the mid-1940s to the late 1950s, relied on glass vacuum tubes to carry out logic and switching operations, since transistors and integrated circuits had not yet been invented. For main memory, these machines used rotating drums coated with magnetic material, where data was recorded as magnetised spots on the drum's surface and read as it spun past a fixed head, since faster memory technologies like magnetic core memory were not yet widely deployed.

Machines built with transistors instead of vacuum tubes belong to the second generation, a technology that made computers smaller, faster, and more reliable, and that generation typically used magnetic core memory rather than drums. The third generation replaced individual transistors with integrated circuits, packing many transistors onto a single chip, and moved even further away from drum-based memory. The fourth generation is defined by the microprocessor, where an entire central processing unit is built onto a single chip, a technology far removed from vacuum tubes and magnetic drums.

The pairing of "vacuum tubes" with "magnetic drums" is the specific signal to watch for in this type of question, since each generation is tied to one dominant processing technology and one dominant memory technology, and only the earliest generation combines these particular two.