Are C versions backwards compatible?

Question

I'm a beginner in C and I was wondering if C versions are backwards compatible so I know if I watch the correct type of tutorials.

Answer 1

backwards compatible? mostly no
forwards compatible? mostly yes

What I mean is

When the C workgroup (WG14) publishes a new standard, most of the programs that were compatible with the previous standard are also compatible with the new standard.

However, new programs written according to the new standard do not necessarily comply with the older standard(s).

In other words... you can (mostly) write C89 and compile with any compiler (C89, C94, C99, C11, C17, C2x); however if you write C17 it may have features that are not available in C11 or previous.