A pointer is a variable whose value is the address of another variable. Like any variable or constant, you must declare a pointer before you can work with it. pointer points the memory location of another variable .
Here, type is the pointer’s base type; it must be a valid C++ type and varname is the name of the pointer variable. The asterisk you used to declare a pointer is the same asterisk that you use for multiplication. However, in this
statement the asterisk is being used to designate a variable as a pointer.
Following are the valid pointer declaration:
int *ip; // pointer to an integer
double *dp; // pointer to a double
float *fp; // pointer to a float
char *ch // pointer to character
The actual data type of the value of all pointers, whether integer, float,
character, or otherwise, is the same, a long hexadecimal number that represents a memory address. The only difference between pointers of different data types is the data type of the variable or constant that the pointer points to.
Using Pointers in C++
There are few important operations, which we will do with the pointers very frequently. (a) We define a pointer variable. (b) Assign the address of a variable to a pointer. (c) Finally access the value at the address available in the pointer variable. This is done by using unary operator * that returns the value of the variable located at the address specified by its operand. Following example makes use of these operations:
#include <iostream>
using namespace std;
int main ()
{
int var = 20; // actual variable declaration.
int *ip; // pointer variable
ip = &var; // store address of var in pointer variable
cout << “Value of var variable: “;
cout << var << endl;
// print the address stored in ip pointer variable
cout << “Address stored in ip variable: “;
cout << ip << endl;
// access the value at the address available in pointer
cout << “Value of *ip variable: “;
cout << *ip << endl;
return 0;
}
When the above code is compiled and executed, it produces result something as follows:
Value of var variable: 20
Address stored in ip variable: 0xbfc601ac
Value of *ip variable: 20
