Question

What is the output produced by the following code? int *p1, *p2; p1 = new int; p2 = new int; *p1 = 10; *p2 = 20; cout << *p1 << " " << *p2 << endl; *p1 = *p2; //This is different from Exercise 4 cout << *p1 << " " << *p2 << endl; *p1 = 30; cout << *p1 << " " << *p2 << endl;

Short answer

Answer: The output of the C++ code snippet will be: ``` 10 20 20 20 30 20 ```

Step-by-step solution

Understand the code and Identify the statements that may produce output

The code provided uses pointers `p1` and `p2` to allocate memory for integers, and the `cout` statement is used to print the values to which these pointers are pointing. Since `cout` is responsible for printing the output, we will focus on the lines containing `cout` statements.

Execute the code step by step and note the values of *p1 and *p2 after each step

Let's go through the code step by step, and note the values of `*p1` and `*p2` after each step: 1. `int *p1, *p2;` - Declare two pointers `p1` and `p2`. 2. `p1 = new int;` - Allocate memory for an integer and assign its address to `p1`. 3. `p2 = new int;` - Allocate memory for another integer and assign its address to `p2`. 4. `*p1 = 10;` - Assign the value 10 to the memory pointed by `p1`. 5. `*p2 = 20;` - Assign the value 20 to the memory pointed by `p2`. 6. `cout << *p1 << " " << *p2 << endl;` - At this point, *p1=10 and *p2=20, so the output will be `10 20`. 7. `*p1 = *p2;` - Assign the value pointed by `p2` to the memory pointed by `p1`. Now *p1=*p2=20. 8. `cout << *p1 << " " << *p2 << endl;` - At this point, *p1=20 and *p2=20, so the output will be `20 20`. 9. `*p1 = 30;` - Assign the value 30 to the memory pointed by `p1`. Now *p1=30. 10. `cout << *p1 << " " << *p2 << endl;` - At this point, *p1=30 and *p2=20, so the output will be `30 20`. So, the final output of the code will be: ``` 10 20 20 20 30 20 ```

Key concepts

Pointers in C++

In C++, pointers are variables that store the memory addresses of other variables. They are a powerful feature that allows you to directly interact with memory. Understanding pointers is crucial for managing dynamic memory allocation and performing operations with memory addresses.

For example, in the code snippet provided, the declaration int *p1, *p2; introduces two pointers, p1 and p2, that will point to integer values. Pointers need to be dereferenced using the * operator to access or modify the value they point to, such as in *p1 = 10;, which assigns the value of 10 to the location in memory pointed to by p1.

It's essential to always initialize pointers and ensure they point to valid memory locations before dereferencing them to prevent undefined behaviors.

Dynamic Memory Allocation

Dynamic memory allocation in C++ is a process by which memory is allocated during the runtime of the program. This can be achieved using operators such as new and delete. Unlike static memory allocation, where the size of the data structure is fixed at compile-time, dynamic memory allocation allows for more flexible memory usage.

For instance, in the provided code, new int dynamically allocates space for an integer and returns its address, which is stored in the pointers p1 and p2. This allocated memory stays valid until it is explicitly deallocated using delete, which prevents memory leaks. Remember to always pair new with delete when you're done using the allocated memory.

Basic C++ Output

C++ uses output streams to display data to various destinations such as the console, files, or even network connections. The standard output stream cout, included in , is used for printing to the console. By using the insertion operator <<, you can send data to cout and it will be displayed on the screen.

In the exercise, cout is coupled with the insertion operator to print the values that pointers p1 and p2 are referencing. This operation forms the basic C++ output and the final result is viewed in the console. The output is formatted using strings and the newline character endl to ensure that each new result is printed on a separate line.

Pointer Assignment

Pointer assignment is the process of assigning a value to a location in memory that the pointer points to, or changing the memory address that the pointer holds. In C++, pointer assignment is done using the assignment operator =.

When assigning the value of one pointer to another, as in *p1 = *p2;, you are copying the value stored at the memory location pointed to by p2 to the memory location pointed to by p1. This does not change where the pointers p1 and p2 are pointing; it just copies the value between the two locations. After this operation, the two pointers still have distinct memory addresses associated with them but contain the same value.