C

C Programming

Master the fundamentals of C programming with comprehensive tutorials, examples, and hands-on exercises

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C Programming Tutorial
Getting Started
Fundamentals
Control Flow
Functions
Arrays & Strings
Pointers
Advanced Topics

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
← Pointer Arithmetic Structures →

Frequently Asked Questions

C is a powerful, general-purpose programming language that's been around since the 1970s. It's the foundation for many modern languages and is essential for system programming, embedded systems, and understanding how computers work at a low level. Learning C gives you a solid foundation in programming fundamentals.

No prior programming experience is required! Our C programming tutorial is designed for complete beginners. We start with the basics and gradually progress to more advanced topics. However, having some basic computer literacy and logical thinking skills will be helpful.

You need a C compiler to run C programs. For beginners, we recommend using our online C compiler which requires no installation. For local development, you can use GCC (GNU Compiler Collection) which is available on Windows (via MinGW), macOS (via Xcode), and Linux. IDEs like Code::Blocks, Dev-C++, or Visual Studio Code are also helpful.

The time to learn C depends on your dedication and prior experience. With consistent practice (1-2 hours daily), you can grasp the basics in 2-4 weeks and become proficient in 2-3 months. Mastering advanced concepts like pointers, memory management, and data structures may take 6-12 months of regular practice.

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.

Absolutely! C remains highly relevant and is consistently ranked among the top programming languages. It's essential for system programming, embedded systems, IoT devices, and performance-critical applications. Many modern languages are built on C, and understanding C helps you become a better programmer overall.