Introduction to Programming in C

📘 File Handling in C (fopen, fscanf, fprintf, etc.)

File handling in C allows a program to perform input and output with files stored on disk. Instead of reading or writing from the terminal, you can work with permanent data using FILE operations like fopen(), fclose(), fprintf(), fscanf(), fread(), and fwrite().

🔹 Why Use File Handling?

• To store and retrieve data permanently.
• For logging, reporting, configuration, etc.
• To read/write large data from/to external storage.

📁 Opening a File: fopen()

fopen() opens a file and returns a pointer to a FILE structure.

FILE *fp;
fp = fopen("data.txt", "r");  // open for reading

📝 Writing to a File: fprintf()

FILE *fp = fopen("notes.txt", "w");
fprintf(fp, "Welcome to UdaanPath!");
fclose(fp);

📖 Reading from a File: fscanf()

char text[100];
FILE *fp = fopen("notes.txt", "r");
fscanf(fp, "%s", text);
printf("Read: %s", text);
fclose(fp);

📚 Example: Logging UdaanPath User Registrations

#include <stdio.h>

int main() {
    FILE *log = fopen("udaanpath_users.txt", "a");
    if (log == NULL) {
        printf("File not found!\n");
        return 1;
    }

    char name[50];
    printf("Enter user name: ");
    scanf("%s", name);

    fprintf(log, "New user: %s\n", name);
    fclose(log);

    printf("User %s added successfully!\n", name);
    return 0;
}

🧹 Closing a File: fclose()

Always close the file using fclose(fp) after reading/writing to free up system resources.

📦 Binary File Handling

C also supports binary file operations using fread() and fwrite().

fwrite(&student, sizeof(student), 1, fp);
fread(&student, sizeof(student), 1, fp);

📝 Practice Questions

1. Create a file and write your name, age, and location.
2. Read a file and print its contents word by word.
3. Append student roll numbers and names to a file.
4. Use fwrite() to store struct data in binary format.

✅ Summary

• Use FILE * to create a file pointer.
• fopen() opens, fclose() closes the file.
• fprintf() writes, fscanf() reads formatted data.
• Check if fopen() returned NULL before file operations.

🚀 Coming Next

In the next chapter, we’ll understand how to handle Command Line Arguments in C — passing arguments to your program via the terminal.