C++ Pointers and References

Pointers

• Why pointers
  • Faster array operation
  • Access large blocks of data out of functions
  • Allocate memory space dynamically at runtime
• Declare and initialize a pointer
  • long* pnumber = NULL;
  • long* pnumber2 = &number2;
• Assign memory address to a pointer
  • Using the address-of operator (&)
  • pnumber = &number;
• Obtain value pointed to by a pointer
  • Use de-reference operator (*)
  • *pnumber++;
• A pointer should ALWAYS be initialized. Otherwise, it might contains random value.
• Example
  
int* pnum1 = NULL;
int num1 = 10;
pnum1 = & num1;
++*pnum1;
*pnum1 += 10
cout << "num1 is now: " << num1 << endl;
// num1 should be 21

• Pointers to char
  • char* can be initialized with a string literal
  • char* pproverb = “A miss is as good as a mile”;
    • Ends with \0
    • // Print out the string
    • cout << pprover << endl;

References

• A reference is an alias for another variable
  • so the variable it’s referencing needs to be declared first
  • a reference can’t be reassigned to another variable
• Declare and initialize
  • long number = 0;
  • long& rnumber = number; // rnumber is an alias to number now
  • rnumber += 10; // same as number += 10;
• If we use pointer then
  • long number = 0;
  • long* pnumber = &number; // pnumber stores the address of number variable
  • *pnumber += 10; // pnumber has to be de-referenced