Programming Concepts (Language-Agnostic)

What is a program?
Source code vs. compiled code vs. interpreted code
Variables & data types
Operators
Control flow (if/else, switch)
Loops (for, while, do-while)
Functions / procedures
Scope & lifetime of variables
Recursion
Stack vs. Heap memory
Pointers & references (conceptually)
Error handling & exceptions
Debugging basics
Comments & documentation