Question

Look at the following array definition. int numbers \([5]=11,2,31\) A) What value is stored in numbers [2]\(?\) B) What value is stored in numbers [4]\(?\)

Short answer

Answer: The value stored in numbers[2] is 31, and the value stored in numbers[4] is 0.

Step-by-step solution

Find the values at the indices

We are given the array definition `int numbers[5] = {11, 2, 31}`, and we want to find out the values at indices 2 and 4.

Value at index 2

In order to find the value at index 2, we need to look at the third value of the array. In this case, the value is 31. So, numbers[2] = 31.

Value at index 4

The given array has only three elements assigned, so the last two elements will have the default value for int data type in C++. The default value for int data type is 0 (zero). Therefore, numbers[4] = 0. So, the answers to the questions are: A) The value stored in numbers[2] is 31. B) The value stored in numbers[4] is 0.

Key concepts

Default Values in C++

C++ is a flexible programming language that offers various features, including default values for array types. Understanding default values is crucial, especially when dealing with arrays, as uninitialized elements can lead to unexpected behavior. When you define an array in C++ without providing explicit values for all indices, the remaining positions are filled with default values. For example, when you declare an integer array and assign values to only some elements, the other indices are automatically initialized with the default value for that data type. The default value for an int in C++ is 0. Let's look at the scenario involving `int numbers[5] = {11, 2, 31}`. Here, you have provided specific values for the first three elements. The array size is declared to be 5, which means two positions are left uninitialized. Due to C++ default behavior, these two indices (in this case, indexes 3 and 4) are automatically set to 0, which explains why `numbers[4]` is equal to 0. So, always be aware of the default initialization rules in C++, as they help prevent unpredictable results and enhance your code's reliability.

C++ Array Initialization

Array initialization is a critical concept in C++ programming. It involves specifying initial values for an array's elements when declaring the array. Not only does this streamline your code, but it also improves performance by reducing the number of uninitialized variables. When you initialize an array, you can do so in various ways. You can choose to:

• Fully initialize all elements at the time of declaration.
• Partially initialize elements, with any remaining taking the default value.
• Use a loop to populate the array with specific values algorithmically.

Consider `int numbers[5] = {11, 2, 31}`. In this declaration, you've only initialized the first three elements of a five-element array. The remaining elements – indexes 3 and 4 – are automatically initialized with their default values, which in this case is 0 for the int type. By mastering array initialization, you'll enhance your ability to control your data structures, leading to more robust and error-free code.

C++ Data Types

C++ is a statically typed language, meaning each variable must be explicitly declared with a data type before use. Data types in C++, such as int, char, float, and double, determine the kind of data a variable can hold and how much space it occupies in memory. This exercise revolves around the integer data type specified by the keyword `int`. Integer variables store whole numerical values, both positive and negative, and by default (without any explicit modification) occupy 4 bytes of memory on most systems. Understanding C++ data types is not just about syntax; it's about optimizing system resources and ensuring the precision of your computations. Knowing the size and range of data types lets you select the most efficient type, thereby avoiding wasted memory and maximizing computational speed. When working with arrays, each element takes on the characteristics of the data type declared. For instance, all elements in an `int` array are integers, meaning operations like arithmetic can be directly applied to them.