[Worldforge-all-lists] [WF-Cpptraining] Advanced - Simple Pointers

[Jonathan W <jwi...@ea...>]

The following STL email requires knowledge
of pointers and I think some other people
besides just the STL branch needs to go over
them.  Don't expect to have a great grasp
over pointers with just this lesson (for
people that aren't already familiar with 'em),
but with more examples you should be able to
get the hang of it.

A variable points to a memmory address.  At
the memory address, the actual data is stored.
To be able to see what the memory address of
a variable is you can:
cout << &theVariable;
The "&" or returns the memory address instead
of the data that is contained in the address.
When reading the operator, you should read it
as "the address of".

To be able to stored the memory address, you
need to declare a pointer with the same type
as the variable that you want to point to.  You
can declare something as a pointer by placing
an asterisk infront of the variable:

int x;
int *x_ptr;

// or for characters

char MiddleInitial;
char *MiddleInitial_ptr;

To give the address of MiddleInitial to the pointer
MiddleInitial_ptr do the following:

MiddleInitial_ptr = &MiddleInitial;

Preferrably by typing, recreate the example at
the end of the email.  Take note of what is printed
out on the screen.

It is *strongly* recommended that you make a
similiar program for the experience.

// BEGINNING OF EXAMPLE
#include <iostream.h>

int main ()
{
  int x;
  int *x_ptr; // x_ptr holds an address, not really int

  x=2;
  x_ptr=&x; // "&" in this case means "the address of"

  *x_ptr*=2;

  cout << "The value of x is " << x << "\n";
  cout << "The address of x is " << &x << "\n";
  cout << "The value of x_ptr is " << x_ptr << "\n";
  cout << "The deference of x_ptr (*x_ptr) is " << *x_ptr << "\n";

  return 0;
}
// END OF EXAMPLE

-- Jonathan Williford


_______________________________________________
cpptraining mailing list
cpp...@ma...
https://mail.worldforge.org/lists/listinfo/cpptraining