Introduction to Programming in C

📘 Strings in C (char[], string.h functions)

In C, strings are arrays of characters that end with a special null character '\0'. While C doesn't have a native string data type like other languages, we can work with character arrays and use helpful functions from the <string.h> library.

🔹 Declaring Strings

char name[10]; // declaration of a string array with 10 characters

📥 Initializing Strings

char city[] = "Delhi";     // implicit null character '\0' at the end
char lang[6] = {'C', 'o', 'd', 'e', '\0'}; // manual initialization

🔁 Reading and Printing Strings

#include <stdio.h>

int main() {
    char name[50];
    printf("Enter your name: ");
    scanf("%s", name); // reads until space
    printf("Welcome, %s!\n", name);
    return 0;
}

Use gets() and fgets() for multi-word input (though gets() is unsafe and deprecated).

📦 Using <string.h> Functions

• strlen(str) – Get string length
• strcpy(dest, src) – Copy one string to another
• strcat(dest, src) – Concatenate strings
• strcmp(str1, str2) – Compare two strings
• strrev(str) – Reverse string (not standard C)

🔎 Example with Multiple Functions

#include <stdio.h>
#include <string.h>

int main() {
    char first[50] = "Hello";
    char second[50] = "World";

    strcat(first, second);  // HelloWorld
    printf("Concatenated: %s\n", first);

    printf("Length: %lu\n", strlen(first));

    if (strcmp(first, "HelloWorld") == 0) {
        printf("Strings match!\n");
    }

    return 0;
}

📚 Real-Life Example (UdaanPath)

Suppose UdaanPath is storing student feedback comments for each course. We use arrays of strings to store and print them:

#include <stdio.h>

int main() {
    char feedbacks[3][100] = {
        "Great course on C programming!",
        "I loved the examples on UdaanPath.",
        "Please add more quizzes."
    };

    printf("📢 UdaanPath Student Feedbacks:\n\n");
    for (int i = 0; i < 3; i++) {
        printf("• %s\n", feedbacks[i]);
    }

    return 0;
}

🧠 Tips

• Always ensure there’s space for '\0' when declaring strings
• Use fgets() over gets() for safe multi-word input
• Use strcmp() with care — returns 0 when strings are equal
• Don't use = for comparing strings — use strcmp() instead

📝 Practice Questions

1. Write a program to count the number of vowels in a string.
2. Create a program to reverse a string without using strrev().
3. Accept two strings from the user and check if they are anagrams.
4. Write a program to copy one string into another.

✅ Summary

• Strings are character arrays ending in '\0'
• Use <string.h> functions to make string operations easier
• Practice input/output and comparisons to build strong logic

🚀 Coming Next

In the next chapter, we’ll dive into Pointers in C — the powerful feature that allows you to manipulate memory directly.