Question

Mark the following statements as true or false. a. In C++, pointer is a reserved word. b. In C++, pointer variables are declared using the word pointer. c. The statement delete p; deallocates the variable pointer p. d. The statement delete p; deallocates the dynamic variable that is pointed to by p. e. Given the declaration: int list[10]; int *p; the statement: p = list; is valid in C++. f. Given the declaration: int *p; the statement: p = new int[50]; dynamically allocates an array of 50 components of type int, and p contains the base address of the array. g. The address of operator returns the address and value of its operand. h. If p is a pointer variable, then the statement p = p * 2; is valid in C++.

Short answer

a. False, b. False, c. False, d. True, e. True, f. True, g. False, h. False.

Step-by-step solution

Evaluate statement a

The statement 'In C++, pointer is a reserved word' is false. In C++, `pointer` is not a reserved word; the `pointers` are variables that store memory addresses, but the term itself is not a keyword.

Evaluate statement b

The statement 'In C++, pointer variables are declared using the word pointer' is false. Pointer variables are declared using an asterisk (*) symbol, not the word `pointer`. For example, `int *p;` declares a pointer `p` that can point to an integer.

Evaluate statement c

The statement 'The statement delete p; deallocates the variable pointer p' is false. The `delete` operator deallocates the memory pointed to by `p`, not the variable `p` itself. The pointer variable `p` still exists after this operation, but it becomes a dangling pointer unless set to `nullptr`.

Evaluate statement d

The statement 'The statement delete p; deallocates the dynamic variable that is pointed to by p' is true. When `delete p;` is executed, it frees the dynamically allocated memory block that `p` is pointing to.

Evaluate statement e

The statement 'The statement: p = list; is valid in C++' is true. In C++, you can assign the name of an array (like `list`) to a pointer. This makes the pointer point to the first element of the array, which is valid.

Evaluate statement f

The statement 'The statement: p = new int[50]; dynamically allocates an array of 50 components of type int, and p contains the base address of the array' is true. This statement allocates memory for 50 integers and assigns the address of the first integer to `p`.

Evaluate statement g

The statement 'The address of operator returns the address and value of its operand' is false. The address of operator `&` only returns the address of its operand, not its value.

Evaluate statement h

The statement 'If p is a pointer variable, then the statement p = p * 2; is valid in C++' is false. In C++, you cannot multiply a pointer with an integer directly. This operation is not valid unless you are doing arithmetic on a dereferenced pointer (not common and not usually meaningful in plain arithmetic terms).

Key concepts

Dynamic Memory Allocation

In C++, dynamic memory allocation is a powerful feature that allows programs to request and release memory as needed during runtime. This is especially useful when the amount of memory required cannot be determined at compile time.
Using the new operator, you can allocate memory for a variable or an array:

• int *p = new int; - Allocates memory for a single integer.
• int *array = new int[10]; - Allocates memory for an array of 10 integers.

After using dynamically allocated memory, you should free it with the delete operator to prevent memory leaks:

• delete p; - Frees the memory pointed to by p.
• delete[] array; - Frees the memory allocated for the array.

Remember, deleting a pointer does not delete the pointer itself, but merely the memory allocated to it.

Pointer Variables

Pointer variables in C++ are special variables that store the memory address of another variable. This allows for indirect access and manipulation of the variable. Declaring a pointer requires the use of an asterisk (*) symbol:

• int *p; - Declares a pointer to an integer.
• double *dp; - Declares a pointer to a double.

The relationship between the pointer and the variable is established by using the address-of operator & to get the address and assigning it to the pointer:

• int x = 10;
• int *p = &x; - Now p points to the address of x.

Pointers can be reassigned to point to different variables throughout their lifecycle.

Array and Pointer Relationship

Arrays and pointers in C++ have a close relationship, where the array name essentially acts as a pointer to its first element. This implies that pointer arithmetic can be conveniently used to traverse an array.
For instance, consider the declaration:

• int list[10]; - Declares an array of 10 integers.

Assigning the array to a pointer makes the pointer reference the first element of the array:

• int *p = list; - Valid statement as list is converted to a pointer pointing to the first element.

This allows for easy iteration over the elements without an explicit loop index.

Pointer Arithmetic

Pointer arithmetic involves operations that manipulate the memory address stored in a pointer variable. Due to the close relationship of arrays and pointers, pointer arithmetic can navigate through elements in a contiguous memory block with ease.
Consider a pointer to an integer array element:

• int *p;
• p = array; - Points to the first element of array.

Using pointer arithmetic, you can access subsequent elements by incrementing the pointer:

• p + 1 - Points to the second element of the array.
• *(p + 2) - Accesses the third element of the array (using dereference).

Arithmetic operations are implicitly scaled by the size of the data type that the pointer is addressing, ensuring it moves by the correct byte count.