Notes / University Notes / Operating System / Chapter 2: OS Structure

Chapter 2: OS Structure

Created: 2025-12-16Updated: 2025-12-16

What the OS offers upward and how it is delivered: system calls as the only door into the kernel, and the structures behind it, monolithic to microkernel.

OS Services

User interface
- Command-Line Interface (CLI)
  - shell: command interpreter, a process that runs in user space
- Graphical User Interface (GUI)
Communication models
- message passing: copy messages between processes through OS (kernel) (system call)
- shared memory: processes share a region of memory for communication (system call)

Application-OS Interface

API - system calls (assembly) - OS kernel
API (Application Programming Interface)
- convenience, portability, efficiency (not too many syscalls)
- can call zero or multiple system calls
- common APIs: Win32 API, POSIX (Portable Operating System Interface for Unix) API, Java API
System Call