C++ has pointers, i.e. variables for other addresses (variables, functions...). In C++, there is an indirect link between arrays and the pointers, that an array identifier is a «constant pointer».

Pointers: – operators * and & – «Arithmetic» of pointers

• Link between arrays and pointers
• Dynamic memory management offered by operators new and delete

int * ad ; // you can also write : int *ad ;
int n ;
n = 20 ;
ad = &n ;
*ad = 30 ; // you can also write : * ad = 30 ;

The following instruction : ad = &n ;

• affects the value of the expression &n to the variable ad. The operator & is a unary operator that provides the result of the address of its operand. Thus, this statement places in the variable ad the address of the n variable.

The following instruction : *ad = 30 ;

• means: assigning to the lvalue ad the value 30. But ad represents the Integer ad address.

Transmission by address

#include <iostream>
using namespace std ;
main()
{ 
    void exchange (int *ad1, int *ad2) ;
    int a=10, b=20 ;
    cout << " before call : " << a << " " << b << "\n" ;
    exchange (&a, &b) ;
    cout << " after call : " << a << " " << b << "\n" ;
}
void exchange (int *ad1, int *ad2)
{ 
    int x ;
    x = *ad1 ;
    *ad1 = *ad2 ;
    *ad2 = x ;
}

Arrays and Pointers

An array name is a constant pointer – In C++, the identifier of an array, when used alone (without index), is considered a (constant) pointer on the beginning of the array.

One-dimensional array

• Consider the following statement : int t[10]
• The notation t is then totally equivalent to &t[0].
• The t identifier is considered to be of the "pointer" type corresponding to the elements of the array, i.e., here, int (and even more precisely const int ).

Two ways to place value 1 in each of the 10 items in our array:

int i ;
for (i=0 ; i<10 ; i++)
    *(t+i) = 1 ;
// Or :
int i ;
int *p :
for (p=t, i=0 ; i<10 ; i++, p++)
    *p = 1 ;

In the second way, we had to copy the value represented by t into a pointer named p. Indeed, the t symbol represents a constant address (t is a pointer type constant on int cases). In other words, an expression such as t++ would have been invalid, just as, for example, 3++. An array name is a constant pointer; it is not lvalue.