Pointer & Strings

Previously we completed the concept of Arrays (parts one, two  three and four), today we will discuss the basics of Pointers.

Pointer Variable Declarations and Initialization

•      Pointer variables:

–     Contain memory addresses as values

–     Normally, variable contains specific value (direct reference)

–     Pointers contain address of variable that has specific value (indirect reference)

•      Indirection

–     Referencing value through pointer

•      Pointer declarations

–     * indicates variable is pointer

int *myPtr;

     declares pointer to int, pointer of type int *

–     Multiple pointers require multiple asterisks

int *myPtr1, *myPtr2;

•      Can declare pointers to any data type

•      Pointer initialization

–     Initialized to 0, NULL, or address

•        0 or NULL points to nothing, and is called ‘Null Pointer’

Pointer Operators:

•& (address operator)

–Returns memory address of its operand

–Example

  int y = 5;
int *yPtr;
yPtr = &y;    // yPtr gets address of y

–yPtr “points to” y

•* (indirection/dereferencing operator)

–*yPtr returns y (because yPtr points to y).

*yptr = 9;      // assigns 9 to y

     cout<<*yptr; 

     cin>>*yptr;

•*  and & are inverses of each other

Calling Functions by Reference

•          3 ways to pass arguments to function

–        Pass-by-value

–        Pass-by-reference with reference arguments

–        Pass-by-reference with pointer arguments

•          Pass-by-reference with pointer arguments

–        Use pointers and indirection/dereferencing operator

–        Pass address of argument using & operator

–        * operator used as alias/nickname for variable inside of function