C is a procedural programming language created in 1972 by Dennis Ritchie. It's known for its efficiency, simplicity, and close-to-hardware nature, making it perfect for systems programming and embedded systems.

Why Learn C?

Foundation: Understand how computers work at a deeper level
Performance: Write fast, efficient code
Embedded Systems: Program microcontrollers and IoT devices
Unix/Linux: Essential for systems programming
Career Prospects: High demand in embedded systems and systems programming

Setup & First Program

Installation:

Windows: Download MinGW or use MSVC compiler
Linux: sudo apt-get install gcc
Mac: Install Xcode Command Line Tools

Your First C Program:

#include 

int main() {
    printf("Hello, C World!\n");
    return 0;
}

Compiling & Running:

gcc program.c -o program
./program

Data Types & Variables

#include 

int main() {
    // Integer types
    int age = 25;           // 4 bytes
    short year = 2025;      // 2 bytes
    long population = 8000000000L; // 8 bytes
    
    // Floating point
    float height = 5.9f;    // 4 bytes
    double pi = 3.14159;    // 8 bytes
    
    // Character
    char initial = 'A';     // 1 byte
    
    // Boolean (using int or stdbool.h)
    int is_student = 1;     // 1 for true, 0 for false
    
    // String (array of characters)
    char name[50] = "John Doe";
    
    // Print values
    printf("Age: %d\n", age);
    printf("Height: %.2f\n", height);
    printf("Initial: %c\n", initial);
    printf("Name: %s\n", name);
    
    return 0;
}

Operators

// Arithmetic operators
int a = 10, b = 3;
printf("a + b = %d\n", a + b);     // 13
printf("a - b = %d\n", a - b);     // 7
printf("a * b = %d\n", a * b);     // 30
printf("a / b = %d\n", a / b);     // 3
printf("a %% b = %d\n", a % b);    // 1

// Comparison operators
printf("a == b: %d\n", a == b);    // 0 (false)
printf("a > b: %d\n", a > b);      // 1 (true)
printf("a != b: %d\n", a != b);    // 1 (true)

// Logical operators
int x = 1, y = 0;
printf("x && y: %d\n", x && y);    // 0 (AND)
printf("x || y: %d\n", x || y);    // 1 (OR)
printf("!x: %d\n", !x);             // 0 (NOT)

// Assignment operators
int c = 5;
c += 3;     // c = c + 3 = 8
c -= 2;     // c = c - 2 = 6
c *= 2;     // c = c * 2 = 12

Control Flow

// If-Else
int age = 18;
if (age >= 18) {
    printf("You are an adult\n");
} else if (age >= 13) {
    printf("You are a teenager\n");
} else {
    printf("You are a child\n");
}

// Switch
int day = 3;
switch (day) {
    case 1:
        printf("Monday\n");
        break;
    case 2:
        printf("Tuesday\n");
        break;
    default:
        printf("Other day\n");
}

// For loop
for (int i = 0; i < 5; i++) {
    printf("%d ", i);    // 0 1 2 3 4
}

// While loop
int count = 0;
while (count < 3) {
    printf("%d ", count);
    count++;
}

// Do-While (executes at least once)
int num = 0;
do {
    printf("%d ", num);
    num++;
} while (num < 3);

Functions

// Function declaration (prototype)
int add(int a, int b);
void greet(char *name);

int main() {
    int result = add(5, 3);
    printf("Sum: %d\n", result);  // 8
    
    greet("Alice");
    return 0;
}

// Function definition
int add(int a, int b) {
    return a + b;
}

void greet(char *name) {
    printf("Hello, %s!\n", name);
}

// Function with multiple return values using pointers
void swap(int *a, int *b) {
    int temp = *a;
    *a = *b;
    *b = temp;
}

Arrays & Strings

// Arrays
int numbers[5] = {1, 2, 3, 4, 5};
printf("%d\n", numbers[0]);    // 1

// Array iteration
for (int i = 0; i < 5; i++) {
    printf("%d ", numbers[i]);
}

// 2D Arrays
int matrix[3][3] = {
    {1, 2, 3},
    {4, 5, 6},
    {7, 8, 9}
};

printf("%d\n", matrix[1][2]);  // 6

// Strings
char str1[20] = "Hello";
char str2[] = "World";

// String functions
#include 
strlen(str1);              // Length
strcpy(str1, str2);        // Copy
strcmp(str1, str2);        // Compare
strcat(str1, str2);        // Concatenate

Pointers

int main() {
    int x = 10;
    int *ptr = &x;      // Pointer to x (& = address of)
    
    printf("x = %d\n", x);           // 10
    printf("Address of x: %p\n", &x);
    printf("ptr = %p\n", ptr);       // Same as &x
    printf("*ptr = %d\n", *ptr);     // 10 (* = dereference)
    
    // Modify value through pointer
    *ptr = 20;
    printf("x = %d\n", x);           // 20
    
    // Array pointers
    int arr[5] = {1, 2, 3, 4, 5};
    int *p = arr;       // Points to first element
    printf("%d\n", *p);  // 1
    printf("%d\n", *(p+1)); // 2
    printf("%d\n", p[2]); // 3
    
    // Pointer to pointer
    int **pp = &ptr;
    printf("%d\n", **pp);  // 20
    
    return 0;
}

Structures

// Define a structure
struct Person {
    char name[50];
    int age;
    float height;
};

int main() {
    // Create and initialize
    struct Person p1 = {"John", 25, 5.9};
    
    // Access members
    printf("Name: %s\n", p1.name);
    printf("Age: %d\n", p1.age);
    
    // Using pointers
    struct Person *ptr = &p1;
    printf("Height: %.1f\n", ptr->height);
    printf("Height: %.1f\n", (*ptr).height);  // Alternative
    
    // Array of structures
    struct Person people[3] = {
        {"Alice", 28, 5.6},
        {"Bob", 30, 6.0},
        {"Carol", 26, 5.4}
    };
    
    for (int i = 0; i < 3; i++) {
        printf("%s: %d years old\n", people[i].name, people[i].age);
    }
    
    return 0;
}

Projects & Practice

Beginner Projects:

Calculator
Number Guessing Game
Temperature Converter
Simple Grade Calculator
Fibonacci Sequence

Intermediate Projects:

Student Management System
Library Management System
File I/O Programs
Sorting Algorithms
Hash Table Implementation

Advanced Projects:

Binary Search Trees
Graph Algorithms
Operating System Basics
Embedded Systems Projects
Game Development (with graphics library)