There's so many different ways to do it, but take for example HIVE, here's a few ways you can work with:
- JavaScript and @hiveio/hive-js
- Python and Beem
For ethereum, their language is Solidity, which you could learn.
Other blockchains and libraries are available, but I usually work in Python and JavaScript so that's why I know of these.
For JS there's more (hive-tx, dhive) and the same with python(lighthive, and then theres hivepy). But the ones you mentioned are probably most popular and maintained.