Operating System Families: Study Guide

I. Overview

Two Dominant Families:

- Unix-like operating systems
- Microsoft Windows

II. Unix-like Operating Systems

Characteristics: Behave like the original Unix OS.

Examples: Linux, macOS, iOS, Android.

History of Unix:
- Developed at Bell Labs in the 1960s.
- Originally for PDP-7 minicomputer, later ported.
- Rewritten in C, enabling portability.
- Supports multiple users, multitasking, and hierarchical directory structure.
- Strong command line shell with standard tools.

Linux:
- Kernel developed by Linus Torvalds.
- Unix-like but doesn't contain Unix source code.
- Open source.
- Bundled with other software to form a Linux distribution.
- Often includes components from the GNU project.

GNU:
- Recursive acronym for "GNU's Not Unix."
- A project to create a free Unix-like OS.
- Complements Linux: Linux provides the kernel, GNU provides other tools (shell, libraries).
- "Linux" often refers to the combination of the Linux kernel and GNU software.

Usage of Linux:
- Common on servers, embedded systems, and with software developers.
- Android OS is based on the Linux kernel.
- Raspberry Pi OS is a Linux distribution.

III. Microsoft Windows

Dominance: Dominant OS on personal computers (desktops, laptops). Strong presence on servers (Windows Server).

Unique History: Doesn't originate from Unix. Early versions based on MS-DOS.

OS/2:
- Joint project with IBM to succeed MS-DOS.
- Microsoft and IBM diverged; IBM took over OS/2.
- Microsoft shifted focus to Windows NT.

Windows NT:
- New kernel, unlike DOS-based Windows.
- Designed to be portable, compatible, support multiple users, and provide security/reliability.
- Led by Dave Cutler (formerly DEC).
- Elements of NT kernel based on DEC's VMS OS.

Evolution of Windows:
- Early Windows NT positioned for business use, coexisting with consumer Windows.
- Shared UI and programming interface.
- Windows XP (2001) brought the NT kernel to consumer Windows.
- All versions of desktop and server Windows since XP are built on the NT kernel.

IV. Common Operating Systems and Their Families

V. Key Terms

Kernel: The core of an operating system.

Distribution: A specific release of an OS, usually referring to Linux.

Open Source: Software with freely available source code.

Command Line Interface (CLI): A text-based interface for interacting with an OS.