Question

Write a C++ statement that prints the message "The number is valid." if the variable grade is within the range 0 through 100 .

Short answer

Question: Write a C++ statement that would print "The number is valid." if the variable grade is within the range of 0 through 100. Answer: ```if (grade >= 0 && grade <= 100) { cout << "The number is valid." << endl; }```

Step-by-step solution

(Step 1: Declare and Initialize)

First, let's declare and initialize a variable named grade: int grade = some_grade_value;

(Step 2: Check the grade's range)

Now, we will check whether the grade is within the range of 0 through 100 with the help of if statement and logical expressions.

(Step 3: Write the if statement)

Here's the if statement combined with the range check which prints the required message if the condition is true: ```cpp #include using namespace std; int main() { int grade = 45; // replace 45 with the desired grade value if (grade >= 0 && grade <= 100) { cout << "The number is valid." << endl; } return 0; } ``` Replace the grade value with the desired grade value. This program will output "The number is valid." if the grade is within the range of 0 through 100.

Key concepts

If Statement in C++

An *if statement* in C++ is a way to make decisions in your code. It allows you to execute a section of code only if a certain condition is met. The general form of an if statement looks like this: ```cpp if (condition) { // code to execute if condition is true } ``` If the "condition" inside the parentheses is true, the code inside the curly braces will run. If it is false, the program will skip this block of code and move on to the next part of your program.

If statements are particularly useful when you need to check if variables meet certain criteria, such as being within a specific range as seen in the example "if the grade is within 0 to 100". By using an if statement, we check whether our variable meets this range condition, allowing our program to react accordingly.

Logical Expressions

Logical expressions are used in programming to combine multiple conditions. In C++, logical expressions often use logical operators such as `&&`, `||`, and `!` which correspond to AND, OR, and NOT, respectively.

- **AND (`&&`)**: This operator returns true if both conditions are true. For example, the expression `(grade >= 0 && grade <= 100)` will only be true if the grade is greater than or equal to 0 *and* less than or equal to 100. - **OR (`||`)**: This operator returns true if at least one of the conditions is true. - **NOT (`!`)**: This operator negates a condition, turning true into false, and vice versa.

These logical operators are essential for creating complex conditions within if statements. They allow you to check multiple criteria at once, providing powerful ways to validate data or make decisions in your program.

Range Checking

Range checking is a technique used to determine whether a value falls within a specified range. In many programming tasks, especially those involving user input or data validation, ensuring that a variable is within an acceptable range is crucial.

In C++, range checking can be efficiently performed using if statements combined with logical expressions. Let's break down the key aspects:

• Define the lower and upper bounds of your acceptable range.
• Use an if statement to check whether the value falls within these bounds. This involves using the `>=` and `<=` operators to compare the value against the bounds.

The example code snippet `if (grade >= 0 && grade <= 100)` illustrates range checking by ensuring the variable *grade* is not less than 0 and not greater than 100. If both conditions are satisfied, the program considers the value valid and executes the corresponding code block.