enter default values instead of passing to Function

[CPP amateur]

Default arguments are those arguments that are substituted for the missing arguments in the function call. Is it possible to enter default values, instead of providing them in the function prototype / function header?
Help me

[JosAH]

Default arguments are those arguments that are substituted for the missing arguments in the function call. Is it possible to enter default values, instead of providing them in the function prototype / function header?
Help me

If you don't mind using some pointers:

int def_p= 42; // the "default default"
 
void f(int* p= &def_p) { // function with a default parameter
   cout << *p << endl;
}
 
void set_def_p(int val= 0) { def_p= val; } // change the default
 
int main() {
 
   set_def_p(54);
   f();
}

kind regards,

Jos