March 14, 1955 — Bell Labs Announces the First Transistor Computer

On March 14, 1955, Bell Telephone Laboratories announced TRADIC — the first fully transistorized digital computer. The name TRADIC stood for TRAnsistor DIgital Computer.

At the time, most computers were built using vacuum tubes. These machines were large, consumed huge amounts of electricity, and failed often. TRADIC showed that computers could be built using transistors instead.

The computer itself

TRADIC was completed in 1954 and publicly announced the following year.

The machine used about 800 transistors and around 10,000 germanium diodes. It consumed less than 100 watts of power, which was extremely small compared with earlier computers.

The computer could perform hundreds of thousands of logical operations per second. Bell Labs also built a special airborne version for the U.S. Air Force, demonstrating that transistor computers could operate in environments where vacuum tube machines would fail.

Vacuum tubes vs transistors

The transition from vacuum tubes to transistors was one of the most important technological shifts in computing.

Size. Vacuum tubes were large glass components. Early computers used thousands of them and filled entire rooms. Transistors were tiny semiconductor devices, making it possible to build much smaller machines.

Power consumption. Vacuum tubes required heated filaments and consumed large amounts of electricity. Transistors used far less power, making computers significantly more efficient.

Reliability. Vacuum tubes failed frequently and required constant maintenance. Transistors were solid-state devices with no fragile filaments, which made them much more reliable.

Heat. Tube computers produced enormous amounts of heat and required large cooling systems. Transistor computers generated much less heat and could be built in more compact systems.

Why TRADIC mattered

TRADIC was not a commercial machine, but it proved an essential idea: a computer could be built entirely from transistors.

This experiment helped start the transition to transistor-based computers in the late 1950s. That transition eventually led to integrated circuits, microprocessors, and modern personal computers.