Logic in circuits
Already in his master's thesis in 1937 he showed that electrical circuits with relays could compute using Boolean logic, that is, with the values yes and no. This laid the foundation for the design of all digital chips.
The bit and the channel limit
At Bell Labs he published his theory of information in 1948. He introduced the bit as the basic unit of information and calculated the highest speed at which data could reliably be sent through a given channel. Engineers still try to get as close as possible to this Shannon limit in every The modem and dial-up internet, Wi-Fi connection and mobile network.
Ciphers, chess and juggling
Shannon also wrote a foundational paper on cryptography, underlying modern cryptography, and in 1950 an article on how to program a computer to play chess. He built an electronic mouse called Theseus that learned to navigate a maze, and in his spare time he rode a unicycle and juggled.