Using return codes - Mini Project: Build & Apply

Using return codes

📖 Scenario: You are writing a small program that simulates a simple login system. The program checks if a username and password are correct and returns a code to indicate success or failure.

🎯 Goal: Build a C program that uses return codes from a function to indicate if login was successful or not.

📋 What You'll Learn

Create a function that checks username and password and returns 0 for success and 1 for failure

Use variables to store the correct username and password

Call the function with test username and password

Print the return code to show if login succeeded or failed

💡 Why This Matters

🌍 Real World

Return codes are used in many programs to signal if an operation succeeded or failed, like login systems, file operations, or network requests.

💼 Career

Understanding return codes helps in debugging and writing clear, maintainable code that communicates status between functions and modules.

1

Create variables for correct username and password

Create two char arrays called correct_username and correct_password with values "admin" and "1234" respectively.

C

// Your code here

Need a hint?

Use char arrays to store text strings in C.

2

Create a function to check login and return codes

Write a function called check_login that takes two char* parameters named username and password. The function should return 0 if both match correct_username and correct_password, otherwise return 1.

C

char correct_username[] = "admin";
char correct_password[] = "1234";

// Write the check_login function below

Need a hint?

Use strcmp from string.h to compare strings. Return 0 for success, 1 for failure.

3

Call the function with test values

Create two char* variables called test_user and test_pass with values "admin" and "1234". Then call check_login(test_user, test_pass) and store the result in an int variable called result.

C

char correct_username[] = "admin";
char correct_password[] = "1234";

int check_login(char* username, char* password) {
    if (strcmp(username, correct_username) == 0 && strcmp(password, correct_password) == 0) {
        return 0;
    } else {
        return 1;
    }
}

// Create test_user and test_pass and call check_login

Need a hint?

Use string pointers for test username and password. Store the function return in result.

4

Print the return code result

Write a printf statement to print "Login result: %d\n" with the variable result.

C

char correct_username[] = "admin";
char correct_password[] = "1234";

int check_login(char* username, char* password) {
    if (strcmp(username, correct_username) == 0 && strcmp(password, correct_password) == 0) {
        return 0;
    } else {
        return 1;
    }
}

char* test_user = "admin";
char* test_pass = "1234";
int result = check_login(test_user, test_pass);

// Print the result

Need a hint?

Use printf to show the login result number.