Vacuum Tubes from the Atanasoff-Berry Computer
The Atanasoff-Berry Computer (ABC) was the first computer to utilize electronics in carrying out computer operations and digital arithmetic calculations. Previous to the ABC, computing machines used mechanical or electro-mechanical relays. Because computers require thousands of switching operations to solve even simple problems, a faster and more reliable relay was necessary to make computers widely practical. An electronic computer operates primarily by means of devices in which the electrons do the moving rather than the mechanical parts, so the switching can be done much faster. The Atanasoff-Berry Computer employed electronic vacuum tubes for the necessary speed and reliability; electronic computers of the late 20th century use microchips.
A Memory Drum (replica) from the Atanasoff-Berry Computer
The memory drum stored information as electric charges in capacitors that could be read, changed, or refreshed electronically. Each ring of capacitors on the drum stored one number. Today, capacitors are crucial parts of the microchips which make up a computer's dynamic memory.