Developed by John Bardeen, Walter Brattain, and William Shockley at the Bell Laboratories on December 23, 1947. The transistor (short for transfer resistance) is made up of semi-conductors and is a component used to control the amount of current or voltage or used for amplification/modulation or switching of an electronic signal. The picture shows several examples of transistors.
The transistor is the primary building block of all microchips, including your CPU, and is what creates the binary 0's and 1's (bits) your computer uses to communicate and deal with Boolean logic. When placed in different configurations transistors form logic gates, which can be combined into arrays called half adders that can also be combined into full adders.
In 1954, IBM announced it was no longer planning to use vacuum tubes in its computers and introduced its first computer that had 2000 transistors. Transistors replaced vacuum tubes and today are found in virtually all electronic devices.