#include 

int main() {
    printf("Hello, World!\n");

    int a = 10;
    int b = 20;
    printf("Sum = %d\n", a + b);

    return 0;
}
    

C Programming Guide

1. Introduction to C

2. Setting Up the Environment

To start programming in C, you need to set up an environment. You can choose from several IDEs (Integrated Development Environments) such as:

• Dev-C++
• Visual Studio (for Windows)
• Xcode (for macOS)
• GCC (GNU Compiler Collection) for Linux

3. Basic Syntax and Structure

A simple C program consists of functions and statements. The basic structure is as follows:

#include <stdio.h>
  
  int main() {
  printf("Hello, World!\n"); // Output a message
  return 0; // Indicate that the program ended successfully
  }

For a more in-depth understanding, check out Learn C - Hello, World!.

4. Data Types and Variables

C supports several built-in data types:

• int: Integer type
• float: Floating-point type
• double: Double-precision floating-point type
• char: Character type

Declaring variables:

int age = 25;
  float salary = 50000.50;
  char grade = 'A';

5. Control Structures

Control structures dictate the flow of execution in a program:

5.1 Conditional Statements

if (age > 18) {
  printf("Adult\n");
  } else {
  printf("Minor\n");
  }

5.2 Loops

Loops allow repetitive execution of code:

for (int i = 0; i < 5; i++) {
  printf("%d\n", i);
  }

Functions enable code reuse and organization. Here’s how to define and call a function:

void greet() {
  printf("Hello!\n");
  }
  
  int main() {
  greet(); // Calling the function
  return 0;
  }

7. Arrays

Arrays are collections of variables of the same type:

int numbers[5] = {1, 2, 3, 4, 5};
  for (int i = 0; i < 5; i++) {
  printf("%d ", numbers[i]);
  }

8. Pointers

Pointers store memory addresses, allowing for dynamic memory management:

int a = 10;
  int *p = &a; // Pointer to variable a
  printf("%d\n", *p); // Dereference the pointer to get the value of a

To understand pointers better, check out Learn C - Pointers.

9. Structures

Structures allow grouping of different data types:

struct Person {
  char name[50];
  int age;
  };
  
  struct Person p1 = {"Alice", 30};
  printf("Name: %s, Age: %d\n", p1.name, p1.age);

10. File I/O

Reading from and writing to files in C:

#include <stdio.h>
  
  int main() {
  FILE *file = fopen("example.txt", "w");
  fprintf(file, "Hello, File I/O!\n");
  fclose(file);
  return 0;
  }

11. Memory Management

Dynamic memory allocation is done using malloc and free:

#include <stdlib.h>
  
  int main() {
  int *arr = (int *)malloc(5 * sizeof(int));
  for (int i = 0; i < 5; i++) {
    arr[i] = i + 1;
  }
  free(arr); // Always free allocated memory
  return 0;
  }

12. Error Handling

Handle errors gracefully to avoid program crashes:

#include <stdio.h>
  
  int main() {
  FILE *file = fopen("nonexistent.txt", "r");
  if (!file) {
    perror("File opening failed");
    return EXIT_FAILURE;
  }
  fclose(file);
  return 0;
  }

Conclusion

C is an essential language for system-level programming and offers powerful features that require careful management. With this guide, you now have a solid foundation to explore more advanced topics and projects.