Mastering C Programming: A Complete Tutorial for Beginners and Beyond

📘 Chapter 4: Functions, Arrays, and Strings in C

🧠 Introduction

This chapter focuses on three foundational pillars in C programming:

1. Functions – Breaking the program into reusable blocks.
2. Arrays – Handling multiple data items using a single name.
3. Strings – Special arrays to work with sequences of characters.

Together, these components help organize, simplify, and optimize your C programs.

🔧 Part 1: Functions in C

What is a Function?

A function is a self-contained block of code designed to perform a specific task. Functions allow code reuse, readability, modularity, and easier debugging.

🔹 Syntax:

return_type function_name(parameters) {

    // function body

    return value;

}

✅ Example:

int add(int a, int b) {

    return a + b;

}

🔹 Calling a Function:

int sum = add(5, 10);

🔸 Types of Functions

🔹 Function Categories Based on Argument & Return

✅ Example: Argument + Return

int square(int n) {

    return n * n;

}

🔹 Function Declaration (Prototype)

Defines the function signature before main():

int add(int, int);  // declaration

🔹 Recursive Functions

A function that calls itself.

int factorial(int n) {

    if (n == 0) return 1;

    return n * factorial(n - 1);

}

📊 Table: Function Concept Summary

📦 Part 2: Arrays in C

What is an Array?

An array is a collection of homogeneous data elements stored in contiguous memory and accessed using indices.

🔹 Syntax:

data_type array_name[size];

✅ Example:

int marks[5] = {90, 85, 78, 92, 88};

🔹 Accessing Elements

printf("%d", marks[2]); // prints 78

🔹 Declaring & Initializing Arrays

int arr[3];             // Declaration only

int arr[3] = {1, 2, 3}; // Declaration + Initialization

🔹 Iterating Over Arrays

for (int i = 0; i < 5; i++) {

    printf("%d\n", marks[i]);

}

🔹 Multi-Dimensional Arrays

Arrays with more than one index.

int matrix[2][3] = {{1,2,3},{4,5,6}};

📊 Table: Array Concept Summary

✨ Part 3: Strings in C

What is a String?

In C, a string is an array of characters ending with a null character \0.

🔹 Declaring Strings

char name[10] = "Alice";

OR

char name[] = {'A','l','i','c','e','\0'};

🔹 Reading and Printing Strings

✅ Using scanf and printf

char name[20];

scanf("%s", name);

printf("Hello, %s", name);

✅ Using gets() and puts()

char sentence[100];

gets(sentence);      // Reads full line

puts(sentence);      // Prints full line

⚠️ gets() is unsafe and not recommended; use fgets() instead.

🔹 String Functions in <string.h>

✅ Example:

#include <string.h>

char str1[20] = "Hello";

char str2[20] = "World";

strcat(str1, str2);  // str1 = HelloWorld

🧪 Sample Program: Function + Array + String

#include <stdio.h>

#include <string.h>

void printReverse(char str[]) {

    int len = strlen(str);

    for (int i = len - 1; i >= 0; i--) {

        printf("%c", str[i]);

    }

}

int main() {

    char name[50];

    printf("Enter your name: ");

    scanf("%s", name);

    printf("Reversed name: ");

    printReverse(name);

    return 0;

}

🧠 Real-World Applications

📋 Chapter Summary Table