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

In C++, 'pointer' is not a reserved word. Reserved words are keywords that have a special meaning in the programming language and 'pointer' isn't one of those keywords. Therefore, this statement is false.

Evaluate Statement b

Pointer variables in C++ are declared using the asterisk (*) symbol, not the word 'pointer'. Therefore, this statement is false.

Evaluate Statement c

The statement 'delete p;' does not deallocate the pointer variable 'p' itself. It deallocates the memory that 'p' is pointing to. Thus, this statement is false.

Evaluate Statement d

The statement 'delete p;' deallocates the memory that is currently pointed to by 'p', provided 'p' was allocated using 'new'. This statement is true.

Evaluate Statement e

In C++, arrays can be implicitly converted to pointers pointing to their first element. Therefore, the statement 'p = list;' where 'list' is an array, is valid. This statement is true.

Evaluate Statement f

The statement 'p = new int[50];' dynamically allocates an array of 50 integers and 'p' receives the address of the first element in this array. Therefore, this statement is true.

Evaluate Statement g

The address of operator (&) in C++ returns only the address of its operand, not the value. Thus, this statement is false.

Evaluate Statement h

Pointers cannot be directly multiplied by integers in C++. Therefore, the statement 'p = p * 2;' is invalid. Thus, this statement is false.

Key concepts

Pointer Variables

Pointer variables in C++ are a key concept in understanding how memory management works in programming. Instead of holding a regular data value, a pointer variable stores the memory address of another variable. This allows for efficient data manipulation, as it provides direct access to memory locations. When declaring a pointer variable, you use the asterisk symbol (*) before the variable name, such as

• int *ptr;

This declaration means ptr is a pointer to an integer type. Note that the location of the asterisk relative to the variable name or type doesn't affect its functionality, but consistency is key for readability.
Pointer variables can point to variables, arrays, or even other pointers. They are critical in dynamic memory operations, allowing programmers to create data structures like linked lists, trees, and graphs that require adjustable memory allocation.

Dynamic Memory Allocation

Dynamic memory allocation in C++ enables programs to request memory during runtime, which is indispensable for efficient memory use. This is crucial in scenarios where the size of data structures cannot be determined ahead of time. C++ uses the new operator to allocate memory dynamically. For example, for allocating memory for an array of integers:

• int *arr = new int[10];

This allocates an array of 10 integers and assigns the base address of this array to the pointer arr.
Once dynamically allocated memory is no longer needed, it should be deallocated using the delete operator to avoid memory leaks. For example, deallocating an array would look like this:

• delete[] arr;

Proper management of dynamic memory using new and delete is a fundamental skill in C++ programming.

Address Operator

The address operator, represented by an ampersand (&), is used in C++ to obtain the memory address of a variable. This operator is crucial in understanding where variables are stored in memory. When used in conjunction with pointer variables, it helps establish a link between regular and pointer variables.

• Example: Given int var = 20;, &var will produce the memory address where var is stored.

The result of using the address operator is a pointer that points to the original variable, facilitating operations like modifying the variable's value directly through its memory address. Note, though, that the address operator only provides the address, not the actual data value.

Arrays and Pointers in C++

Arrays and pointers in C++ have a very close relationship. While treating arrays, one has to understand they can be implicitly converted to pointers that point to their first element. This is particularly useful when passing arrays to functions.

• For example, with int numbers[5];, using int *ptr = numbers; is valid. Here, ptr will point to the first element of the array numbers.

Even though arrays and pointers can often be used interchangeably in expressions, they're fundamentally different. Arrays have a fixed size and cannot be reassigned, while pointers can be reassigned and manipulated, which makes pointers more flexible.

• This flexibility is one of the reasons why pointers are used extensively in dynamic data structures.