Looking for the font of this book programming section

[Doom Ronie]

The code is from a C++ book

I must say that is a book made by a programming community and there is no author to ask about the font.

There is no information about how the book was written.

Thank you !

[Riccardo Sartori]

Roboto Mono.

[Doom Ronie]

Thank you very much. How do you recognise the fonts ? You succed everytime.