Operating Systems Introduction

Role of an operating system

An OS is a resource manager between hardware and applications. It handles CPU scheduling, memory management, file storage, networking, and security.

• Abstraction: files, processes, sockets.
• Isolation: one app crash should not kill the system.
• Efficiency: maximize throughput and responsiveness.

Kernel and user mode

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

int main(void) {
  pid_t pid = getpid(); // user-space app calling kernel API
  printf("Current PID: %d
", pid);
  return 0;
}