C System Programming Tutorial

1. Introduction to System Programming

System programming involves writing software that interacts with hardware and system resources. This includes tasks like process management, memory management, and file manipulation.

In C, system programming is made possible by direct access to low-level system calls and libraries that interact with the operating system.

2. Process Management in C

Processes are fundamental to system programming. In C, processes are managed through system calls like `fork()`, `exec()`, and `wait()`.

#include <stdio.h>
#include <unistd.h>

int main() {
    pid_t pid = fork();
    
    if (pid == 0) {
        // Child process
        printf("Child process\n");
    } else {
        // Parent process
        printf("Parent process\n");
    }
    return 0;
}
                

This simple program demonstrates how to create a new process using `fork()`, which splits the execution flow into a parent and a child process.

3. File Handling in C

System programming also involves working with files and managing file descriptors. In C, file handling is done using functions like `open()`, `read()`, `write()`, and `close()`.

#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>

int main() {
    int fd = open("file.txt", O_RDONLY);
    if (fd == -1) {
        perror("Error opening file");
        return 1;
    }

    char buffer[100];
    read(fd, buffer, sizeof(buffer));
    printf("File contents: %s\n", buffer);

    close(fd);
    return 0;
}

This example demonstrates how to open a file, read its contents, and then close the file using file descriptors.

4. Memory Management in C

Memory management is critical in system programming. C provides direct access to memory using pointers, as well as dynamic memory management with functions like `malloc()` and `free()`.

#include <stdio.h>
#include <stdlib.h>

int main() {
    int *ptr = (int*)malloc(sizeof(int));
    if (ptr == NULL) {
        printf("Memory allocation failed\n");
        return 1;
    }

    *ptr = 100;
    printf("Allocated memory value: %d\n", *ptr);

    free(ptr);  // Free the allocated memory
    return 0;
}

This code demonstrates how to allocate memory dynamically using `malloc()` and release it with `free()`.

5. Conclusion

C system programming allows developers to interact directly with the operating system to manage processes, memory, and file operations. Mastering system programming in C is essential for building efficient and resource-aware software.