# Operating Systems
### What is an operating system?

An operating system is software that manages and organizes that computer's resources and basic functions, including:
* Providing a user interface
* Managing memory
* Processing tasks
* Keeping itself secure
* Managing peripherals (e.g. printers, external hard drives)
* Multi-Tasking
* Managing Errors
* Etc.
Operating systems are based on kernels - the core of the OS, which runs software and manages the hardware of the computer.

## Operating System List
### Unix

Operating system Unix was developed by a group of employees from Bell Labs under the guidance of Dennis Ritchie, Ken Thompson and Brian Kernighan in 1969. This operating system was created under the fundamentals of simplicity as they had few people working on the project and wanted to complete it relatively quickly. The design standards set by Unix paved the way for the modern computing world (except Windows).

### BSD

At the end of 1970's, the University of California, Berkeley made a number of improvements to the source code of UNIX, including the work with protocols of TCP/IP. Their work was known as BSD (Berkeley Software Distribution). It spread under licence, allowing to refine and improve the product and transfer the result to third parties, with or without source codes, provided that authorship of the code written in Berkeley is indicated. While there was some legal trouble, the case was ruled in favor of the Regents of California and that set a precedent that Unix-like operating systems are not under copyright so long as they contain no original Unix source code. Thus the BSD project had to remove all Unix based code from 4.4 BSD terming their new creation 4.4BSD lite. This BSD was limited in features so projects like FreeBSD and NetBSD sprung up to fill in the gaps.

### Amiga OS

The operating system for Amiga-based personal computers (Motorola 68000 processor) has an atypical microkernel called Exec. Classic AmigaOS is considered to be a combination of two components: Kickstart and Workbench.
Kickstart provides abstraction from Amiga's unique hardware and contains: a displacing preemptive multitasking scheduler (Exec), a disk operating system (AmigaDOS) and a graphical interface library (Intuition).
Workbench is a graphical user interface, and is usually presented with a desktop of the same name or another file manager.
The history of AmigaOS begins in 1984. It was the first operating system in which real-time preemptive multitasking, a graphical user interface, and a command line were simultaneously implemented. It has 3 full branches (inheriting the AmigaOS architecture):
* AROS - AmigaOS-compatible OS at API level, developed by AROS Team on the principles of Open-Source (x86 processors).
* AmigaOS 4.x - a version of the proprietary AmigaOS, developed by Hyperion Ent. for the AmigaONE PC family (PowerPC processor);
** AmigaAnywhere is a cross-platform application environment similar to Java. It exists for all processors;
* MorphOS - AmigaOS-compatible OS mixed with Open-Source type, originally developed by Genesi for the Pegasos PC family (PowerPC processor);

### DOS

In 1980, QDOS (Quick and Dirty Operating System) was created by Tim Paterson of Seattle Computer Products (SCP). QDOS, for the most part, was a 16-bit clone of CP/M, but with a new filesystem - FAT. QDOS was renamed to 86-DOS, because it was designed to work on an Intel 8086 processor. Microsoft acquired QDOS for $ 60,000 and sold it to IBM as PC-DOS (MS-DOS).
August 1, 1984 IBM announces the release of a new generation of personal computers - IBM PC/AT.

### Free DOS

Free DOS - free-to-use functional copy of a known MS-DOS operating system.

### FreeBSD

FreeBSD is a Unix-free operating system descending from 4.4 BSD lite which was created at UC Berkeley. FreeBSD has many interesting features such as jails and ZFS. As a BSD, FreeBSD is licensed under the BSD license and as anyone may take any portion of it into a different project, even if that other project is not open source. Many companies such as Sony (playstation) and Apple are known to use a portion of FreeBSD code.

### Mac OS

Mac OS - is a Unix operating system system developed by Apple Computers Co. in 1984, under the name "System 1". In 1997, the 8th version of the operating system was released, and the operating system was changed to Mac OS (Full name: Macintosh Operating System).

### macOS

macOS is the tenth release of the Mac OS line being developed and manufactured by the American company Apple Computers Co. (Today: Apple Inc.) Unlike Mac OS 9, macOS X was developed on the XNU core, and had code from FreeBSD and OpenStep. macOS went through several naming iterations - Mac OS X, OS X and macOS. The current version of macOS is macOS 12.2 Monterey.

### Microsoft Windows

Microsoft Windows is a family of Microsoft operating systems. Was created for IBM computers with MS-DOS support, basically being a graphical shell for MS-DOS, up until Windows XP. Windows 1.0, 2.0, 3.0 and 3.1 were all graphical shells for DOS. Windows 95, 98 and ME (Millennium Edition) were all based on the 9x kernel, which ran under MS-DOS. Windows NT 4.0 and Windows 2000, both business-oriented Windows versions, ran under the NT Kernel. Today, Windows runs on the NT Kernel, no matter if it is consumer or business oriented, and has been running on NT since Windows XP. The latest version of Windows is Windows 11.

### IBM OS/2

OS/2 is an operating system developed by IBM (initially jointly with Microsoft, later independently). Currently, work on client versions has been discontinued due to the widespread use of the Windows NT family of operating systems. Server versions continue to be supported. It was widely used in the USA, in the banking and manufacturing sectors.

### ReactOS

ReactOS is an operating system, one of the projects of the Open Source community, dating back to FreeWin95. During the development it was planned to achieve full compatibility with Microsoft Windows NT 4 applications and drivers. It is an open operating system based on the principles of the Windows NT® architecture (such Microsoft products as Windows XP, Windows 7, Windows Server 2012 are built on the Windows NT architecture). The system was developed from scratch, and thus is not based on Linux and has nothing to do with the UNIX architecture.

### Plan 9

Plan 9 is an operating system developed at Bell Labs - the cradle of UNIX and the C language. Built on the idea of using file hierarchies to represent any operating system and hardware resources. Ideal for building distributed systems.

### Inferno OS

Inferno - the successor of the Plan9's ideas, a distinctive feature of which is the small requirements for computer resources and the ability to work both on top of the installed OS and independently.

### Menuet OS

Menuet is a standalone operating system written in assembly language. The 64-bit version is commercial and requires payment.

### KolibriOS

Kolibri is a branch of Menuet OS, but unlike Menuet, it is completely free.

### iOS

iOS - (until June 24, 2010 - iPhone OS) is a proprietary mobile operating system for smartphones, electronic tablets, wearable players and some other devices based on the Darwin Kernel, which powers macOS. It is developed and produced by Apple Inc. The latest version of iOS is iOS 15.3.

### Android

Android is an open-source operating system developed by Google Inc, based on the Linux Kernel. Android is available for smartphones, tablets, TVs, watches, TV-Sticks, Set-Top Boxes etc. The latest version of Android is Android 12.

### Ubuntu

Ubuntu is a Linux distribution developed by Canonical Inc, and it's one of the most well known Linux-based operating systems. It is based on Debian - another Linux distribution. The first version of Ubuntu, 4.10, was released on October 20th, 2004. It has several official branches - Kubuntu (uses KDE Plasma as the Desktop Environment), Lubuntu (LXQt), Ubuntu Budgie (Budgie), Ubuntu Kylin (Chinese-only, uses UKUI, a fork of MATE), Ubuntu MATE (MATE), Ubuntu Studio (tailored for multimedia production, uses KDE Plasma) and Xubuntu (XFCE), all of them replacing the default Desktop Environment of Ubuntu (GNOME). The latest version of Ubuntu is 21.10 "Impish Indri".

### Chrome OS

Chrome OS is a closed-source, proprietary operating system developed by Google Inc, based on the Linux Kernel, built for "Chromebooks". Chrome OS is based on an open-sourced version of itself - Chromium OS. Chrome OS is marketed towards schools as a cheap alternative to buying laptops pre-installed with Windows.

## Ideas for the classroom

Ask students to consider the similarities and differences between operating systems - they could make a poster/fact sheet/presentation to illustrate.

## Credits

Big thanks to Esteban16, Marshmallych, Hydriz, SGBookYT, Billinghurst and WikiSystems for creating and changing the Russian page of this site