Function pointers & Callbacks

A function pointer stores the address of a function, allowing that function to be called indirectly, passed as an argument, or stored in a data structure, similar to how a regular pointer stores the address of a variable. Callbacks use this to let one function invoke another that is decided at runtime, a pattern used by standard library functions like qsort, which takes a comparison function as a callback. This mechanism underlies more advanced patterns in C, including simulating object-oriented dispatch through structs containing function pointers.