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Pointers

This guide provides a comprehensive overview of pointers and references in C++. It explains how to locate a variable's memory address using the reference operator (&), which provides a unique address for each variable. It also covers the dereference operator (*), allowing access to values stored at referenced memory locations. The tutorial includes practical examples of pointer variable declaration, initialization, and how to use the indirection operator to interact with variables. Learn how references serve as aliases without requiring additional memory.

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Pointers

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  1. Pointers

  2. Each cell can be easily located in the memory because it has a unique address. Reference operator (&) • The address that locates a variable within memory is what we call a reference to that variable. • This reference can be obtained by preceding the identifier of a variable with an ampersand sign (&), known as reference operator. • Note that using the address/refrenceoperator, &, for a given object creates a pointer to that object. • Example: given that var is an intvariable, &var is address of the object var

  3. Dereference operator (*) • A variable which stores a reference to another variable is called a pointer. • Using a pointer we can directly access the value stored in the variable which it points to. • To do that, precede the pointer's identifier with an asterisk (*), which acts as dereference operator and that can be translated to "value pointed by".

  4. Pointer variable - declaration and initialization • A pointer is an expression that represents both the address and type of another object. • Any pointer is placed during runtime in the specific memory address. • An expression such as &var is a constant pointer; however, C++ allows you to define pointer variables, that is, variables that can store the address of another object. • In a declaration, the star character * always means “pointer to.” • Example: int *ptr; • Pointer variables contain memory addresses as their values.

  5. After declaring a pointer variable, you must point the pointer at a memory address by using the address operator. • Example : inty = 5; // declare variable y int*yPtr; // declare pointer variable yPtr the statement yPtr= &y; // initialize-assign address of y to yPtr

  6. Example

  7. Indirection operator • The indirection operator(dereference operator) * is used to access an object referenced by a pointer: • Given a pointer, ptr, *ptr is the object referenced by ptr. • Example: long a = 10, b, *ptr; ptr= &a; // Let ptr point to a. b = *ptr; • Note : The indirection operator * has high precedence, just like the address operator &. Both operators are unary.

  8. References

  9. DEFINING REFERENCES • A reference is another name, or alias, for an object that already exists. • Defining a reference does not occupy additional memory. • Any operations defined for the reference are performed with the object to which it refers.

  10. The ampersand character, &, is used to define a reference. Given that T is a type, T& denotes a reference to T. • Example: float x = 10.7; float& rx = x; //The place contents the value 10.7. have two names and one address. cout<<x<< endl; //output: 10.7 cout<<&x<<endl; //address of x in memory cout<<rx<< endl; // output: 10.7 cout<<&rx<< endl; //address of x in memory = &x

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