Question

Look at the following array definition. \\[\text { int numbers }[1]=\\{2,4,6,8,10\\}\\] What will the following statement display? cout \( < < \star(\text { numbers }+3)<<\) end 1

Short answer

Answer: The output of the given statement is 8.

Step-by-step solution

Understanding array notation and elements

First, we need to understand the array definition that is given: \\[\text { int numbers }[1]=\\{2,4,6,8,10\\}\\] This creates an array called 'numbers' with 5 elements: 2, 4, 6, 8, and 10. Note that the indexing of an array in C++ starts with 0, i.e., numbers[0] represents the first element in the array,(numbers[1] represents the second, and so on.

Interpreting the given statement

The given statement is: cout \( < < \star(\text { numbers }+3)<<\) end 1 Let's break down this statement into its components: 1. `numbers`: This is the given array. 2. `numbers + 3`: This performs pointer arithmetic, adding 3 to the memory address of the first element of the 'numbers' array. 3. `\star (numbers + 3)`: The * symbol is a dereference operator in C++, which gets the value stored at a memory address. Here, it retrieves the value located at the memory address (numbers + 3). 4. `cout << ...`: This part of the statement prints the result obtained from the preceding steps.

Computing the output

Now, let's compute the output of the given statement step by step: 1. 'numbers' refers to the memory address of the first element in the array: 2. 2. When we add 3 to the address of the first element, it points to the fourth element in the array, which is 8. 3. The dereference operator `\star` retrieves the value stored at that memory address: 8. 4. Finally, `cout << ...` prints the result, which is 8. The given statement will display '8' as the output.

Key concepts

Pointer Arithmetic

C++ arrays work closely with pointers, which are variables that store memory addresses. When we perform pointer arithmetic, we modify these memory addresses directly. Consider a starting pointer that points to a specific memory location, such as the address of the first element in an array. By adding a number, say `3`, to this pointer, we skip forward in memory. In the context of arrays, `numbers + 3` means moving three elements ahead from the initial position. If the array contains elements 2, 4, 6, 8, and 10, this operation makes the pointer point to the address of the *fourth* element. This simplified method of navigating memory is powerful because it lets programmers efficiently access elements without complex calculations or additional variables.

Dereferencing Operator

When you have a pointer in C++, it's like having a treasure map pointing to a location. However, knowing the location isn't helpful if you can't see what's there. The dereferencing operator, represented by the `*` symbol, is the tool that lets you see what's at the pointed-to location. If you're using pointer arithmetic to move to a particular element in an array, dereferencing is how you actually access it. Take `*(numbers + 3)` for example. Here, the pointer shows the fourth element's address, and the dereferencing operator retrieves the value `8`, rather than the address itself. Thus, it's essential for accessing the value stored in memory.

Array Indexing

Arrays in C++ are ordered collections of elements, and each element can be accessed using indices, starting from `0`. When using array indexing, numbers like `numbers[0]` indicate an element's position in the array. With array indexing, you can directly specify which element to retrieve. However, what makes arrays interesting is their relationship with pointers. Every index in an array corresponds to a calculated memory address, and it's this connection that allows for tricks like pointer arithmetic. For example, `numbers[3]` and `*(numbers + 3)` offer equivalent results. They both access the element `8` in the array using different methods.

Output Display in C++

The `cout` statement in C++ is a simple yet essential tool for outputting data. It acts like a print function, allowing you to display text, numbers, and results to the console. When you mix `cout` with operations like pointer arithmetic and dereferencing, it becomes a powerful way to show the results of your code in progress. In the previously discussed case, `cout << *(numbers + 3) << endl` executes several tasks: it computes the value `8` by the combined use of pointer arithmetic and dereferencing, and then it displays this number. The `endl` is used to end the current output line, ensuring any further output begins on a new line. This combination streamlines your ability to monitor and showcase output directly.