Question

Consider the following array definition: int values[5] = { 4, 7, 6, 8, 2 }; What does each of the following statements display? cout << values[4] << endl; __________ cout << (values[2] + values[3]) << endl; __________ cout << ++values[1] << endl; __________

Short answer

Answer: The outputs are: Statement 1: 2 Statement 2: 14 Statement 3: 8

Step-by-step solution

Recall the array values

The given array is int values[5] = {4, 7, 6, 8, 2}; which has five elements with indices 0 to 4.

Analyze the first statement

The first statement is cout << values[4] << endl;. We need to find the value at index 4 of the "values" array. In our array, the element at index 4 is 2. So, the statement will output 2.

Analyze the second statement

The second statement is cout << (values[2] + values[3]) << endl;. To find the output of this statement, we need to add the values at index 2 and index 3 of the "values" array. In our array, the element at index 2 is 6 and the element at index 3 is 8. So, the statement will output 6 + 8 = 14.

Analyze the third statement

The third statement is cout << ++values[1] << endl;. This statement has a pre-increment operator on the value at index 1 of the "values" array. In our array, the element at index 1 is 7. The pre-increment operation increases the value by 1 before the expression is evaluated. So, the statement will output 7 + 1 = 8.

Conclusion

The outputs for the given statements are: Statement 1: 2 Statement 2: 14 Statement 3: 8

Key concepts

Array Indexing

Working with arrays in C++ is a common task, and understanding indexing is crucial for accessing data correctly. An array is simply a collection of items stored at contiguous memory locations, and each item is called an element. In C++, the first element of the array is at index 0, not 1. So, when we refer to an element using an index such as

• "values[4]",

it implies accessing the fifth element in the array (since indices start at zero).
In the example:

• int values[5] = {4, 7, 6, 8, 2};

We used values[4] to get the element 2. Gaining a solid understanding of array indexing will help avoid common pitfalls, such as accessing out-of-bound indices, which could result in unpredictable behavior or program crashes.

Pre-Increment Operator

In C++, the pre-increment operator is represented by "++" placed before a variable. This operation increases the value of the variable by one, and the incremented value is used right away in an expression. For example, in the statement

• cout << ++values[1] << endl;

the pre-increment operator is applied to values[1], which initially holds the value 7.
Before printing, the value at this index is increased to 8, hence, the output of the expression is 8.
Using the pre-increment operator can be particularly useful in loops or when you need to update a value and use the updated value immediately in further calculations.

Output Statements

Understanding how to use output statements is fundamental in programming, as they allow us to see results and debug effectively. The cout statement in C++ is used to display messages or values to the standard output, usually the console. The symbol "<<" is known as the insertion operator and is used with cout to join text and variable outputs together.

• For instance, cout << "Hello, World!" << endl; will display "Hello, World!" on the screen.

In the provided examples, complex expressions like

• cout << (values[2] + values[3]) << endl;

can be output directly, where it computes the sum of values before displaying on the console.
Including endl at the end of the statement ensures that any further console output starts on a new line. Such knowledge not only aids in understanding output on the console but also in formatting it to be more readable to users.