C Tutorial — Learn C Programming
Key takeaway: This free C tutorial teaches you systems programming from scratch — variables, pointers, arrays, functions, structs, and memory management — with practical code examples you can compile and run.
C is a general-purpose, procedural programming language created in 1972. It is used for operating systems, embedded systems, game engines, and performance-critical applications. This tutorial is for beginners, CS students, and developers who want to understand how computers work at a low level.
Last updated: September 2026
Dynamic Memory Allocation in C
Dynamic memory allocation allows you to allocate memory during runtime. This is essential for creating flexible programs that can handle varying amounts of data.
malloc() - Memory Allocation
Basic malloc() Usage
#include <stdio.h>
#include <stdlib.h>
int main() {
int n;
printf("Enter number of elements: ");
scanf("%d", &n);
// Allocate memory for n integers
int *arr = (int*)malloc(n * sizeof(int));
if (arr == NULL) {
printf("Memory allocation failed!\n");
return 1;
}
// Input elements
printf("Enter %d elements: ", n);
for (int i = 0; i < n; i++) {
scanf("%d", &arr[i]);
}
// Display elements
printf("You entered: ");
for (int i = 0; i < n; i++) {
printf("%d ", arr[i]);
}
printf("\n");
// Free allocated memory
free(arr);
return 0;
}calloc() - Initialized Allocation
calloc() vs malloc()
#include <stdio.h>
#include <stdlib.h>
int main() {
int n = 5;
// Using malloc (uninitialized)
int *arr1 = (int*)malloc(n * sizeof(int));
printf("malloc array (uninitialized): ");
for (int i = 0; i < n; i++) {
printf("%d ", arr1[i]); // Garbage values
}
printf("\n");
// Using calloc (initialized to zero)
int *arr2 = (int*)calloc(n, sizeof(int));
printf("calloc array (zero-initialized): ");
for (int i = 0; i < n; i++) {
printf("%d ", arr2[i]); // All zeros
}
printf("\n");
// Initialize malloc array manually
for (int i = 0; i < n; i++) {
arr1[i] = i + 1;
}
printf("Initialized malloc array: ");
for (int i = 0; i < n; i++) {
printf("%d ", arr1[i]);
}
printf("\n");
free(arr1);
free(arr2);
return 0;
}realloc() - Resize Memory
Dynamic Array Resizing
#include <stdio.h>
#include <stdlib.h>
int main() {
int *arr;
int size = 3;
int newSize = 6;
// Initial allocation
arr = (int*)malloc(size * sizeof(int));
// Initialize with values
for (int i = 0; i < size; i++) {
arr[i] = i + 1;
}
printf("Original array: ");
for (int i = 0; i < size; i++) {
printf("%d ", arr[i]);
}
printf("\n");
// Resize array
arr = (int*)realloc(arr, newSize * sizeof(int));
if (arr == NULL) {
printf("Reallocation failed!\n");
return 1;
}
// Initialize new elements
for (int i = size; i < newSize; i++) {
arr[i] = i + 1;
}
printf("Resized array: ");
for (int i = 0; i < newSize; i++) {
printf("%d ", arr[i]);
}
printf("\n");
free(arr);
return 0;
}Dynamic 2D Array
2D Dynamic Array
#include <stdio.h>
#include <stdlib.h>
int main() {
int rows = 3, cols = 4;
// Allocate memory for array of pointers
int **matrix = (int**)malloc(rows * sizeof(int*));
// Allocate memory for each row
for (int i = 0; i < rows; i++) {
matrix[i] = (int*)malloc(cols * sizeof(int));
}
// Initialize matrix
int value = 1;
for (int i = 0; i < rows; i++) {
for (int j = 0; j < cols; j++) {
matrix[i][j] = value++;
}
}
// Display matrix
printf("Dynamic 2D Array:\n");
for (int i = 0; i < rows; i++) {
for (int j = 0; j < cols; j++) {
printf("%3d ", matrix[i][j]);
}
printf("\n");
}
// Free memory
for (int i = 0; i < rows; i++) {
free(matrix[i]);
}
free(matrix);
return 0;
}Memory Management Rules:
- Always check if allocation was successful (pointer != NULL)
- Always free dynamically allocated memory with free()
- Don't use freed memory (dangling pointers)
- Don't free the same memory twice
- Set pointers to NULL after freeing
Frequently Asked Questions
C is a foundational systems programming language that's been around since the 1970s. It's the base for Linux, Windows, and most operating systems. Learning C gives you deep understanding of memory, pointers, and how computers work — skills that transfer to every other language. According to the TIOBE Index, C consistently ranks in the top 2 most popular languages.
No, zero experience needed. Our C programming tutorial is designed for complete beginners. We start with Hello World and gradually progress to pointers and memory management. Basic computer literacy and logical thinking are helpful but not required.
Just a C compiler — or use our free online compiler. For beginners, our online C compiler requires no installation. For local development, use GCC (available on all platforms). IDEs like VS Code, Code::Blocks, or Dev-C++ also work well.
2–4 weeks for basics, 3–6 months for proficiency. With 1–2 hours daily practice, you can learn syntax, loops, and functions in a few weeks. Mastering pointers, memory management, and data structures takes 6–12 months. Practice with our C programming examples.
C programming skills open doors to various career paths including system programming, embedded systems development, operating system development, device driver programming, game development, and firmware development. Many companies in automotive, aerospace, telecommunications, and IoT sectors actively seek C programmers.
Yes, extremely relevant. C consistently ranks in the top 2 on TIOBE and powers Linux, embedded systems, IoT, automotive software, and game engines. Understanding C makes you a better programmer in any language since most runtimes (Python, Java, Node.js) are themselves written in C.