ALGOL W
ALGOL W is a general-purpose programming language that was designed for scientific and system programming. It was primarily used for numerical computations and algorithm development.
Hello, world code example:
begin
write( "Hello world!" )
end.
Popularity: Less than 1% of developers are using or have used this language.*
*According to StackOverflow's 2023 survey.
Repositories on GitHub: 8,670,830