What eliminates the need to place a function definition before all calls to the function?

In programming languages that support function declarations or prototypes, such as C and C++, the need to place a function definition before all calls is eliminated. By declaring a function before its first use, the compiler knows about the function's signature, allowing calls to be made regardless of the order of definitions. This enables better organization of code and modular programming, as functions can be defined later in the file or in separate files.