Deadfish

Deadfish is an esoteric programming language that consists of only four commands: i, d, s, and o which stand for increment, decrement, square, and output respectively. It is mainly used for educational purposes and for programming challenges to test understanding and creativity in solving problems with a limited set of commands.

Popularity: Less than 1% of developers are using or have used this language.*
*According to StackOverflow's 2023 survey.