Before transistors, early computers like the ENIAC used thousands of vacuum tubes to process data.

The Electronic Numerical Integrator and Computer (ENIAC) was designed by John Mauchly and J. Presper Eckert at the University of Pennsylvania. It contained 17,468 vacuum tubes, 7,200 crystal diodes, and 1,500 relays. Because vacuum tubes operated like light bulbs, they produced immense heat, requiring the ENIAC to use dedicated forced-air cooling systems to prevent the hardware from melting.The machine consumed roughly 150 kilowatts of electricity, which was enough to power a small town. Reliability was a major issue because at least one tube failed nearly every day, requiring technicians to hunt through the massive 30-ton structure to find the broken component. A single calculation could take hours to set up because the machine had to be manually programmed using thousands of switches and cables.The breakthrough came in December 1947 at Bell Labs, where John Bardeen, Walter Brattain, and William Shockley demonstrated the first working point-contact transistor. Unlike vacuum tubes, transistors are solid-state devices that do not require a vacuum or a heated filament to function. This transition allowed engineers to shrink computer components from the size of a thumb to a microscopic scale.By the late 1950s, the Philco Transac S-2000 and the IBM 7090 became some of the first fully transistorized commercial computers. This shift reduced power consumption by over 90 percent and increased processing speeds exponentially. Today, a single modern microprocessor can contain over 50 billion transistors, a feat that would be physically impossible using vacuum tube technology.