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2.2: How to use a pointer

  • Page ID
    34647
  • How to use a pointer?

    • Define a pointer variable – you must use an asterisk (*) when defining a pointer variable. All three of the following are valid – they are the same:
      • int *ptr;
      • int * ptr;
      • int* ptr;
    • Assigning the address of a variable to a pointer using unary operator (&) which returns the address of that variable.
    • Accessing the value stored in the address using unary operator (*) which returns the value of the variable located at the address specified by its operand.

    The reason we associate data type to a pointer is that it knows how many bytes the data is stored in. When we increment a pointer, we increase the pointer by the size of data type to which it points.

    how a pointer contains the address of a variable

     

    // C++ program to illustrate Pointers in C++
    #include <iostream>
    using namespace std;
    
    int main()
    {
        int var = 20; 
    
        // declare pointer variable    
        int *ptr; // assignment happens at time of definition:
                       // it would be: int *ptr = &var;
    
        // note that data type of ptr and var must be same
        // also note the absence of the * during this assignment
        ptr = &var;    
    
      
    
        // assign the address of a variable to a pointer
        cout << "Value at ptr = " << ptr << endl;
        cout << "Value at var =" << var<< endl;
        cout << "Value at *ptr =" << *ptr<< endl;     
        
        return 0;
    
    }

    Output:

    Value at ptr = 0x7ffcb9e9ea4c
    Value at var = 20
    Value at *ptr = 20

     

    Adapted from:

    "Pointers in C/C++ with Examples" by Abhirav Kariya, Geeks for Geeks is licensed under CC BY 4.0

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