Goto statements in C

⚠️ The Goto Statement in C Programming

Powerful but controversial control flow

The goto statement in C allows you to transfer control to a labeled statement within the same function. While it can be a powerful tool, it is generally considered bad practice to use goto because it can make the code less readable and harder to understand. It can lead to unstructured code and make debugging more challenging.

⚠️

Why Avoid Goto?

• Makes code less readable and harder to understand
• Can lead to unstructured, "spaghetti" code
• Makes debugging more challenging
• Goes against structured programming principles

💡 Example (Not Recommended)

#include <stdio.h>
int main() {
    int num;

    // Ask the user to enter a positive number
    printf("Enter a positive number: ");
    scanf("%d", &num);

    // Check if the number is positive
    if (num <= 0) {
        printf("Invalid input. Please enter a positive number.\n");

        // Use goto to jump back to the input prompt
        goto input_prompt;
    }

    // Display the entered positive number
    printf("You entered: %d\n", num);

    return 0;

    // Label for the goto statement
    input_prompt:
    // Re-prompt the user for input
    printf("Enter a positive number: ");
    scanf("%d", &num);

    // Continue with the rest of the program...
}

🔍 How This Example Works

Step 1: The program asks the user to enter a positive number using printf and scanf.

Step 2: It checks if the entered number is positive. If it's not, it prints an error message and uses goto to jump to the label input_prompt.

Step 3: The label input_prompt: is placed after the return 0; statement, but the program can still jump to it using goto.

Step 4: The program then re-prompts the user for input and continues with the rest of the program.

✅

Better Alternative: Use Structured Control Flow

While this example demonstrates the use of goto, it's important to note that in most cases, using structured control flow (such as loops and conditional statements) is a better practice for writing maintainable and readable code.

🌟 Recommended Approach (Using do-while Loop):

#include <stdio.h>
int main() {
    int num;

    // Use a do-while loop for input validation
    do {
        printf("Enter a positive number: ");
        scanf("%d", &num);

        if (num <= 0) {
            printf("Invalid input. Please try again.\n");
        }
    } while (num <= 0);

    // Display the entered positive number
    printf("You entered: %d\n", num);

    return 0;
}

🎯 Why This is Better:

• Cleaner Structure: No jumping around in code
• Easy to Follow: Linear execution flow
• Maintainable: Easy to modify and debug
• Standard Practice: Follows structured programming principles

🎯 Key Takeaways

⚠️ Avoid goto whenever possible - it makes code hard to follow

✅ Use loops and conditions instead for better code structure

💡 Structured programming leads to more maintainable code