Comment by JCharante

Have you ever been to a Marriott? They have something called MARSHA depending on the property. Once you log in it's basically a command line interface filled with abbreviations. As a high schooler in 2016 I used to train people at a reservations call center on how to use Marsha. It's super unintuitive but surprisingly everyone can wrap their heads around it eventually. Ok maybe 9 out of 10. You could decline to learn Marsha and work for properties that use a GUI like Opera PMS (for us it was mainly IHG properties). You got a pay raise if you learned Marsha. Opera was great, they later started upgrading to some bloated crap with lots of padding between buttons.

IIRC Marsha has transactions so you can build up a reservation and make queries in the process. There's even test properties in production so you can practice making/reserving/retrieving reservations.