Before using a function, a prototype declaration is necessary. At this time, the types of the parameters should also be declared.

extern void func1();

void g()

{

    func1(1); // Error

}

extern void func1(int);

void g()

{

    func1(1); // OK

}

Whereas in C programs const type objects are linked externally, in C++ programs they are linked internally. In addition, const type objects require initial values.

const cvalue1;     // Error

const cvalue2 = 1; // Links internally

const cvalue1 = 0;        // Gives initial value

extern const cvalue2 = 1; // Links externally as a C program

In C++ programs, if explicit casting is not used, assignment of pointers to other objects (excluding pointers to functions and to members) is not possible.

void func(void *ptrv, int *ptri)

{

    ptri = ptrv; // Error

}

void func(void *ptrv, int *ptri)

{

    ptri = (int *)ptrv; // OK

}