Question

Consider the following statement: int *num; a. Write the C++ statement that dynamically creates an array of 10 components of type int and num contains the base address of the array. b. Write a C++ code that inputs data into the array num from the standard input device. c. Write a C++ statement that deallocates the memory space of array to which num points.

Short answer

Use `new int[10]` to allocate, a `for` loop for input, and `delete[] num;` to deallocate.

Step-by-step solution

Dynamically Allocate Memory

To dynamically create an array of 10 components of type `int` and have `num` point to this array's base address, use the `new` operator in C++. The syntax for creating an array is: ```cpp num = new int[10]; ``` This line of code allocates memory for an array of 10 integers and assigns the base address to the pointer `num`.

Input Data into the Array

After creating the array, you need to populate it with data from the standard input, typically the keyboard. You'll use a loop to iterate over each array element to input data. Use the following code: ```cpp for (int i = 0; i < 10; ++i) { std::cin >> num[i]; } ``` This loop runs 10 times, each time taking an input from the user and storing it in the array position `num[i]`.

Deallocate Memory

To avoid memory leaks, you should deallocate the memory allocated for the array when it's no longer needed. Use the `delete[]` operator followed by the pointer name: ```cpp delete[] num; ``` This statement releases the memory space previously allocated to the array that `num` points to, ensuring efficient memory usage.

Key concepts

Pointers in C++

In C++, pointers are variables that store memory addresses. When you create a pointer like `int *num;`, you are reserving space for an address that points to an `int`. Pointers do not initially point to a meaningful location; they must be assigned an address before they are used effectively. This is done by either pointing to an already existing variable or by dynamically allocating memory. A pointer can be used to reference arrays because the base address of an array is the address of its first element.

In the example given, `num` becomes a pointer to the base address of an array once we allocate memory with `new int[10]`. This address is stored in `num`, allowing direct access to the array elements using pointer arithmetic, which looks like `*(num + i)`, or simply using `num[i]`. Using pointers can make programs more efficient but requires understanding to prevent accessing unassigned memory locations which can lead to undefined behavior.

Array Handling in C++

Arrays in C++ are a sequence of elements of the same data type placed in contiguous memory locations. The powerful thing about arrays is that they allow you to handle multiple related variables with a single name, using an index to distinguish each element.

Once you have dynamically allocated an array using a pointer (`num` in this exercise), you input data into it using a loop. The loop iterates over each index of the array, and elements are typically accessed via the pointer with `num[i]`. This concise method of handling data is crucial as it simplifies processes where data must be processed serially.

• To access elements, use the pointer and the index, like `num[i]`.
• Remember that arrays in C++ are zero-indexed, so the first element is `num[0]`.
• The size of an array should be managed carefully to avoid accessing out-of-bound elements, which leads to errors like undefined behavior or runtime crashes.

Efficiently managing arrays with loops like `for`, allows each element to be accessed, modified, or read during operations, making handling large collections of data practical.

Memory Management in C++

Memory management is a critical part of programming in C++. When you use dynamic memory allocation, as with the `new` operator, it is your responsibility to manage that memory to prevent leaks. A memory leak can occur if you lose the last pointer to a block of allocated memory without deallocating it. This can eventually exhaust available memory.

To prevent this, use the `delete[]` operator to deallocate memory allocated for arrays. When you call `delete[] num;`, all memory previously allocated to the array is returned to the system. This step is crucial once you finish using the array, to make sure your application uses resources efficiently.

Consider the following tips for efficient memory management:

• Always pair `new` with `delete` and `new[]` with `delete[]`.
• After deleting memory, set pointers to `nullptr` to avoid dangling pointers which can cause program crashes if that memory location is accessed later.
• Regularly review your code to ensure memory is being properly allocated and deallocated to maintain optimal performance and resource usage.

By following good memory management practices, you benefit from the power of pointers and dynamic allocations while keeping your programs stable and efficient.