Whenever you call a c function or C++ function, compiler will expect the function definition or function prototype as declaration.
Whether C or C++ programming will allow calling the function without function declaration?
myFunction(); //calling without pre declaration,
Answer is yes in case of C programming(Terms and condition will apply) and answer is no for C++ programming.
Calling function in C programming function declaration:
Function with return type as integral value no need to be declared or defined explicitly in the C programming.
So then what is that terms and conditions?
When your return type is not a integral value, then you have to explicitly define or declare the function . If it is not defined then compiler will throw an error like, I can’t found “function declaration” or “function definition” for the function you called.
Calling function in C++ programming function declaration:
For c++ it will not compile for all return types irrespective of the return type of the function