Hello codeforces!

This post can be off topic for some of you so don't look down( On the screen ). And sorrrrrrrrrry ofcourse.

Can someone provide good notes and preparation resources for OOPS, OS and DBMS. Everyone having resources pls post in the comments many people will get benifitted by this small ( sarcastically small ) contribution of yours. Thank you very much.

Grow Together

UPD0: Downvote me hard from all your alts but provide what I asked for. UPD1: I hate downvoter newbies because they are frustrated with their ratings.