switch Statement in C

Syntax of Switch Statement in C

The switch statement in C allows you to execute different parts of your code depending on the value of a given variable or expression.

Basic Structure of Switch Case Statement in C

The basic structure of a switch statement in C includes the 'switch' keyword, followed by an expression or variable in parentheses, and a block of code enclosed between a pair of curly braces {}. Inside the code block, you'll find various 'case' statements, with each case containing a unique value or constant expression, and the code to be executed if the given value matches the expression. A typical switch statement in C has the following structure: switch (expression) { case constant1: // code block to be executed if expression equals constant1; break; case constant2: // code block to be executed if expression equals constant2; break; ... default: // code block to be executed if none of the case values match the expression; } You can also include a 'default' clause, which is optional but can be beneficial as it offers a fallback option if none of the other case values match the given expression or variable.

Example of Switch Statement in C Programming

To better understand the concept of a switch statement in C, let's explore a few examples showcasing its usage in different scenarios.

Simple Switch Case Example

Suppose you want to create a program that evaluates a user-entered number and displays its equivalent in words. Using a switch statement for this scenario, your code might look like this: #include int main() { int number; printf("Enter a number between 1 and 5: "); scanf("%d", &number); switch (number) { case 1: printf("One"); break; case 2: printf("Two"); break; case 3: printf("Three"); break; case 4: printf("Four"); break; case 5: printf("Five"); break; default: printf("Invalid number, please enter a number between 1 and 5."); } return 0; } In this example, the switch statement evaluates the 'number' variable, and depending on its value, the respective case is executed.

Nested Switch Statement in C

In some situations, you might need to use a switch statement inside another switch statement, known as a nested switch statement. For instance, imagine you want to create a program that converts lowercase letters to their uppercase equivalents and vice versa. Here's an example of a nested switch statement: #include int main() { char userChoice, userInput; printf("Choose 'U' to convert lowercase to uppercase, or 'L' to convert uppercase to lowercase: "); scanf("%c", &userChoice); getchar(); // This is to discard the newline character printf("Enter the character to be converted: "); scanf("%c", &userInput); switch (userChoice) { case 'U': switch (userInput) { case 'a' ... 'z': printf("Uppercase: %c", userInput - 32); break; default: printf("Invalid input for conversion to uppercase."); } break; case 'L': switch (userInput) { case 'A' ... 'Z': printf("Lowercase: %c", userInput + 32); break; default: printf("Invalid input for conversion to lowercase."); } break; default: printf("Invalid choice, please choose 'U' or 'L'."); } return 0; } In this case, the first switch statement evaluates the 'userChoice' variable, and if the user chooses 'U' or 'L', it further evaluates the 'userInput' character within the nested switch statement. Depending on the input, the program displays the converted letter or an error message if the input is not valid.

How the Switch Statement in C Works

The switch statement in C compares a given expression with a set of constant values, and the corresponding code block for the matching constant value is executed. It provides a more structured and efficient way of making decisions based on the comparison.

Comparing Switch Statement with If-Else

When making decisions in C, you can use either the switch statement or the if-else structure. Both can be used to execute specific code blocks depending on conditions, but the switch statement is more efficient and readable in cases where you need to compare a single value or expression with multiple constants. Here are the main differences between the two decision-making structures:

• Expression: In the if-else structure, you can use various relational expressions to compare values, while the switch statement only allows you to test a single expression against constant values.
• Conditions: The switch statement has separate 'case' statements for different constant values, which makes it easier to execute specific code for each value. On the other hand, if-else structures can become more complex and challenging to read when there are multiple conditions and nested if-else statements.
• Efficiency: The switch statement is more efficient than the if-else structure when comparing a single variable or expression to multiple constant values because it directly jumps to the matching case instead of evaluating each condition in a sequential manner as in the if-else structure.
• Break statement: Each case within a switch statement requires a break statement to exit the switch block and avoid executing subsequent cases. In contrast, if-else structures do not require a break statement since they execute only the matching block of code.

Break and Default in Switch Statement

In a switch statement, there are two significant elements to be aware of: the break keyword and the optional default case.

The Break Keyword

A break statement is used at the end of each case block in a switch statement to prevent subsequent cases from being executed. The following list explains the importance and behaviour of the break keyword in switch statements:

• A break statement stops further execution of the code within the switch block once the matching case has been found and executed.
• If a break statement is not used, the program will continue to execute the code of the following cases, even if their values do not match the given expression. This is called "fall-through" behaviour.
• It is essential to insert a break statement at the end of each case block to ensure only the required code is executed, except in cases where you intentionally want the program to fall through to the next case.

The Default Case

The default case is an optional part of the switch statement, which serves as a fallback when the expression's value does not match any of the cases. Here are some key aspects of the default case:

• The default case can be placed anywhere within the switch block, but it is typically located at the end for better readability.
• It is used to handle situations in which the given expression does not match any of the existing cases. Instead of skipping the entire switch block, the program will execute the code within the default case.
• A break statement is not necessary after the default case, as there are no more cases to execute after it. However, adding a break statement is a good programming practice for consistency and to avoid potential fall-through errors if more cases are added in the future.

The break and default elements play crucial roles in controlling the flow of your program when using a switch statement in C, allowing you to manage decisions efficiently based on single expressions or variables.

Switch Statement in C Explained with Practical Examples

Switch statements can be utilized in various coding scenarios to effectively handle decision-making. In this section, we will discuss how switch statements can be used in the context of menu-driven programs and implementing a calculator program.

Using Switch Case for Menu Driven Programs

Menu-driven programs are ubiquitous because they provide a user-friendly interface for interacting with software. A switch statement can be a powerful tool in designing these interfaces, particularly when multiple options are available to the user. Let's examine a practical example of a switch case applied to a menu-driven program for managing bank transactions: #include int main() { float balance = 0; int choice; do { printf("\n1. Deposit\n2. Withdraw\n3. Check Balance\n4. Exit\n"); printf("Enter your choice: "); scanf("%d", &choice); switch (choice) { case 1: { float deposit; printf("Enter deposit amount: "); scanf("%f", &deposit); balance += deposit; printf("Deposit successful. New balance: %.2f\n", balance); break; } case 2: { float withdraw; printf("Enter withdrawal amount: "); scanf("%f", &withdraw); if (withdraw > balance) { printf("Insufficient balance.\n"); } else { balance -= withdraw; printf("Withdrawal successful. New balance: %.2f\n", balance); } break; } case 3: printf("Current balance: %.2f\n", balance); break; case 4: printf("Exiting the program...\n"); break; default: printf("Invalid choice. Please enter a valid option.\n"); break; } } while (choice != 4); return 0; } In this example, the menu-driven program offers various options – deposit, withdrawal, checking balance, and exit – to the user. The program uses a switch statement to process user input and perform the corresponding actions. The switch statement ensures efficient handling of decisions and improves the readability and organization of the code.

Implementing a Calculator with Switch Statement in C

Another practical application of switch statements is implementing a simple calculator program. A calculator requires evaluating and performing mathematical operations based on user inputs. With a switch statement, it becomes easier to manage operations for various choices. Here is an example of a calculator program using a switch statement: #include int main() { float num1, num2, result; char operation; printf("Enter first number: "); scanf("%f", &num1); printf("Enter second number: "); scanf("%f", &num2); printf("Choose an operation (+, -, *, /): "); scanf(" %c", &operation); switch (operation) { case '+': result = num1 + num2; printf("Result: %.2f\n", result); break; case '-': result = num1 - num2; printf("Result: %.2f\n", result); break; case '*': result = num1 * num2; printf("Result: %.2f\n", result); break; case '/': if (num2 == 0) { printf("Division by zero is not allowed.\n"); } else { result = num1 / num2; printf("Result: %.2f\n", result); } break; default: printf("Invalid operation. Please choose a valid operation.\n"); break; } return 0; }

In this calculator program, the user is prompted to input two numbers and choose an operation: addition, subtraction, multiplication, or division. The switch statement evaluates the chosen operation, and the corresponding case performs the calculation. The switch statement provides a concise and organized method of managing decisions in calculator programs.