As you know, I am a fan of Smalltalk programming language. It is one the of first high-level languages ever designed. Also, it’s the first object-oriented programming language.
To get started with Smalltalk, I recommend having a look at Squeak. It’s a free software for developing and running Smalltalk programs.
The other option is Pharo, which is a fork of Squeak in a different direction. It is intended to be more modern with less backward compatibility.
Here is how to write a “Hello World” program using Smalltalk.
Transcript show:'Hello World'.