An object-oriented operating system is in contrast to an object-oriented
user interface or programming
framework, which can be run on a non-object-oriented operating system like
DOS or
Unix.
There are already
object-based language concepts involved in the design of a more typical operating system such as
Unix. While a more traditional language like
C does not support object-orientation as fluidly as more recent languages, the notion of, for example, a
file,
stream, or
device driver (in Unix, each represented as a
file descriptor) can be considered a good example of objects. They are, after all,
abstract data types, with various
methods in the form of
system calls which behavior varies based on the type of object and which implementation details are hidden from the caller.
Object-orientation has been defined as
objects +
inheritance, and inheritance is only one approach to the more general problem of
delegation that occurs in every operating system.[2] Object-orientation has been more widely used in the
user interfaces of operating systems than in their
kernels.
Background
An object is an instance of a class, which provides a certain set of functionalities. Two objects can be differentiated based on the functionalities (or methods) they support. In an operating system context, objects are associated with a resource. Historically, the object-oriented design principles were used in operating systems to provide several protection mechanisms.[1]
Protection mechanisms in an operating system help in providing a clear separation between different user programs. It also protects the operating system from any malicious user program behavior. For example, consider the case of user profiles in an operating system. The user should not have access to resources of another user. The object model deals with these protection issues with each resource acting as an object. Every object can perform only a set of operations. In the context of user profiles, the set of operations is limited by
privilege level of a user.[1]
Present-day operating systems use object-oriented design principles for many components of the system, which includes protection.
Examples
Athene
Athene is an object-based operating system first released in 2000 by Rocklyte Systems.[3][4] The user environment was constructed entirely from objects that are linked together at runtime. Applications for Athene could also be created using this methodology and were commonly scripted using the object scripting language Dynamic Markup Language (DML). Objects could have been shared between processes by creating them in
shared memory and locking them as needed for access. Athene's object framework was multi-platform, allowing it to be used in Windows and Linux environments for developing object-oriented programs. The company went defunct and the project abandoned sometime in 2009.
BeOS
BeOS[5] was an object-oriented operating system released in 1995, which used objects and the
C++ language for the
application programming interface (API). The kernel was written in C with C++ wrappers in user space. The OS did not see mainstream usage and proved commercially unviable, however it has seen continued usage and development by a small enthusiast community.
Choices
Choices is an object-oriented operating system developed at the
University of Illinois at Urbana–Champaign.[6][7] It is written in
C++ and uses objects to represent core kernel components like the
central processing unit (CPU),
processes, and so on.
Inheritance is used to separate the kernel into portable machine-independent classes and small non-portable dependent classes. Choices has been ported to and runs on
SPARC,
x86, and
ARM.
ETHOS
ETHOS was an experimental object oriented version of the Oberon System (see below) created by Clemens Szyperski for his PhD Thesis[8] written in
Oberon-2
GEOS
PC/GEOS is a light-weight object-oriented multitasking graphical operating system with sophisticated window and desktop management featuring scalable fonts. It is mostly written in an object-oriented x86 assembly language dialect and some C/C++ and is designed to run on
DOS (similar to Microsoft Windows up to
Windows Me). GEOS was developed originally by
Berkeley Softworks in 1990, which later became GeoWorks Corporation, and it is continued to be maintained by BreadBox Computer Company. Related
software suites were named Ensemble and New Deal Office. Adaptations exist for various palmtops, and 32-bit systems with non-x86-CPUs.
Haiku
Haiku (originally named OpenBeOS), is an open-source replacement for BeOS. It reached its first development milestone in September 2009 with the release of Haiku R1/Alpha 1. The x86 distribution is compatible with BeOS at both source and binary level. Like BeOS, it is written primarily in
C++ and provides an object-oriented API. It is actively developed.
IBM i (OS/400, i5/OS)
IBM introduced
OS/400 in 1988. This OS ran exclusively on the
AS/400 platform. Renamed
IBM i in 2008, this operating system and runs exclusively on
Power Systems which also can run
AIX and
Linux. IBM i uses an object-oriented methodology and integrates a database (
Db2 for i). The IBM i OS has a 128-bit unique identifier for each object.
IBM OS/2 2.0
IBM's first priority based pre-emptive multitasking, graphical, windows-based operating system included an object-oriented user shell. It was designed for the Intel 80386 that used
virtual 8086 mode with full 32-bit support and was released in 1992.
ArcaOS, a new OS/2 based operating system initially called Blue Lion[9] is being developed by Arca Noae. The first version was released in May 2017.
IBM TopView
TopView was an object-oriented operating environment that loaded on a PC on DOS, and then took control from DOS. At that point it effectively became an object-oriented operating system with an object-oriented API (TopView API). It was IBM's first multi-tasking, window based, object-oriented operating system for the PC led by David C. Morrill and released in February 1985.
Java-based
Given that
Oracle's (formerly
Sun Microsystems')
Java is today one of the most dominant object-oriented languages, it is no surprise that Java-based operating systems have been attempted. In this area, ideally, the
kernel would consist of the bare minimum needed to support a
Java virtual machine (JVM). This is the only component of such an operating system that would have to be written in a language other than Java. Built on the JVM and basic hardware support, it would be possible to write the rest of the operating system in Java; even parts of the system that are more traditionally written in a lower-level language such as C, for example
device drivers, can be written in Java.
Examples of attempts at such an operating system include
JavaOS, JOS,[10] JNode, and
JX.
Xerox developed several workstations with an operating system written in
Interlisp-D. Interlisp-D provided object-oriented extensions like LOOPS and CLOS.
Movitz and
Mezzano are two more recent attempts at operating systems written in Common Lisp.
The
Object Manager is in charge of managing NT objects. As part of this responsibility, it maintains an internal
namespace where various operating system components, device drivers, and
Win32 programs can store and lookup objects. The NT
Native API provides routines that allow
user space (mode) programs to browse the namespace and query the status of objects located there, but the interfaces are undocumented.[16] NT supports per-object (file, function, and role)
access control lists allowing a rich set of security permissions to be applied to systems and services. WinObj is a Windows NT program that uses the NT Native API (provided by NTDLL.DLL) to access and display information on the NT Object Manager's name space.[17]
Object Linking and Embedding (OLE) was part of a grander plan named
Cairo, the code name for a project at Microsoft from 1991 to 1996. Its charter was to build technologies for a next generation operating system that would fulfill
Bill Gates' vision of "information at your fingertips".[18][19] Cairo
never shipped, although parts of its technologies have since appeared in other products. The
Windows 95graphical user interface was based on the initial design work that was done on the Cairo user interface. The remaining component is the
object-based file system. It was once planned to be implemented in the form of Windows Future Storage (
WinFS) as part of
Windows Vista. WinFS is the code name for data storage and
management system project based on
relational databases, running on the Windows NT
file system (
NTFS), which is object-oriented in that it can store the NT objects including its NT object identifier. Each NTFS object has an object identifier; a shortcut with a target that's on an NTFS volume also records the object identifier of the shortcut target, and the object identifier of the drive.[20] WinFS was first demonstrated in 2003 as an advanced storage subsystem for the
Microsoft Windowsoperating system, designed for
persistence and management of
structured,
semi-structured, and
unstructured data. WinFS development was cancelled in June 2006, with some of its technologies merged into other Microsoft products such as
Microsoft SQL Server 2008 and
Microsoft SharePoint. It was subsequently confirmed in an interview with Bill Gates that Microsoft planned to migrate applications like
Windows Media Player,
Windows Photo Gallery,
Microsoft Office Outlook, etc., to use
WinFS as the data storage back-end.[21]
NeXTSTEP
During the late 1980s,
Steve Jobs formed the computer company
NeXT. One of NeXT's first tasks was to design an object-oriented operating system,
NeXTSTEP. They did this by adding an object-oriented framework on
Mach and
BSD using the
Objective-C language as a basis. It achieved a niche status in the computing market, notably used by
Tim Berners-Lee developing the first implementation of the
World Wide Web.
OpenStep was provided as an API layer on many operating systems, namely
HP-UX, NextStep,
Solaris, and Windows.
Oberon System
Oberon System is a single user, object-oriented operating system made for the
Ceres line of
workstations (processor:
National SemiconductorNS32000), developed in the later 1980s at
ETH Zurich by
Niklaus Wirth and
Jürg Gutknecht. It is built entirely from modules of the programming language
Oberon.[22] There are two successors of the Oberon System, ETHOS (see above) and, as of 2023 still maintained, an evolution named Active Object System (AOS),[23] then renamed Bluebottle, then renamed A2.
OOSMOS
The Object-Oriented State Machine Operating System (OOSMOS), written in C, promotes object-oriented encapsulation and implements a full table-driven hierarchical state machine architecture. It generates C code directly from state charts drawn with the open source tool
UMLet. OOSMOS also supports a unique feature call 'state threads' which allows a thread of execution per state. OOSMOS operates on a bare board or in cooperation with an existing operating system.
Phantom OS
Phantom OS adheres to a principle where "everything is an object" and eliminates the concept of a file entirely, instead transparently persisting virtual memory to storage.
ReactOS
ReactOS is an open-source operating system intended to be binary compatible with application software and
device drivers made for Microsoft Windows NT versions. Written from scratch, it aims to follow the
architecture of Windows NT designed by Microsoft from the hardware level right through to the application level. This is not a Linux-based system, and shares none of the
unix architecture.[24][25]
Smalltalk
Smalltalk was invented at
Xerox in the 1970s. The Smalltalk system is fully object-oriented and needs very little support by
BIOS and the
run-time system.
Syllable
Syllable makes heavy use of
C++ and for that reason is often compared to
BeOS.
Taligent was an object-oriented operating system project, begun by
Apple Inc. and jointly developed with
IBM in the 1990s. It was later spun off to an IBM subsidiary and transformed from an operating system to a programming environment.
^Wegner, Peter (December 1987). "Dimensions of Object-based Language Design". ACM SIGPLAN Notices. 22 (12): 168–182.
doi:
10.1145/38807.38823. Also in Conference Proceedings on Object-oriented Programming Systems, Languages.
^"About". JOS (A Free Java-Based Operating System). Retrieved 2012-09-03. The JOS Project is a collaborative undertaking by an international group of Java™ programmers and enthusiasts aimed at the creation of a free and open Java™ based Operating System (JOS). As a collaborative effort, we work together to research how a Java-based operating system should work. Together, we work to build components for a Java-based operating system.
^
Knudsen, Svend Erik (25 October 2000). "Medos in Retrospect". In Böszörményi, László;
Gutknecht, Jürg; Pomberger, Gustav (eds.). The School of Niklaus Wirth: The Art of Simplicity. Morgan Kaufmann. pp. 69–86.
ISBN978-1558607231.
ISBN1-55860-723-4 & dpunkt,
ISBN3-932588-85-1.
^"Object-Based". Microsoft Hardware Development Centre. Retrieved Aug 23, 2015.
^Nebbett, Gary (February 20, 2000). Windows NT/2000 Native API Reference. Sams Publishing. p. 528.
ISBN978-1578701995. The Windows NT/2000 Native API Reference provides the first comprehensive look at these undocumented services. A unique tool for software developers, this reference includes documentation of over 200 routines included in the native API, detailed description of routines that are either not directly accessible via the Win32 API, or that offer substantial additional functionality.
^Russinovich, Mark.
"Windows Sysinternals WinObj". Microsoft. Retrieved 2014-05-16. Obj is a must-have tool if you are a system administrator concerned about security, a developer tracking down object-related problems, or just curious about the Object Manager namespace.
^Gates, Bill (1994).
""Information at Your Fingertips" #2 Keynote (The Road Ahead) – Comdex 1994". Microsoft. Retrieved 2014-05-16. Bill Gates' "Information At Your Fingertips" keynote speech for Comdex 1995 became the basis for his book The Road Ahead, predicting the next decade in technology – right and wrong. These predictions are enlivened by the interaction between Gates speaking and a made-for-Comdex future crime show.
^Chen, Raymond (2007).
"Windows Confidential: The NT Way (excerpts from "The Old New Thing" book)". Microsoft. Retrieved 2014-05-16. The Windows NT file system folks looked at the Windows 95 shortcut resolution algorithm and scoffed. " We can do better than that: We're object-oriented!" Each NTFS object has an object identifier; a shortcut with a target that's on an NTFS volume also records the object identifier of the shortcut target, as well as the object identifier of the drive itself.
^Friedl, Klemens.
"About ReactOS: Object Based". ReactOS Project. Retrieved 2017-02-19. ReactOS uses an object metaphor that is pervasive throughout the architecture of the system. Not only are all of the things in the UNIX file metaphor viewed as objects by ReactOS, but so are things such as processes and threads, shared memory segments, the global registry database and even access rights.
^Filby, J. "ReactOS: An open-source alternative to NT?." IEEE Software 16.1 (1999): 35–35.
An object-oriented operating system is in contrast to an object-oriented
user interface or programming
framework, which can be run on a non-object-oriented operating system like
DOS or
Unix.
There are already
object-based language concepts involved in the design of a more typical operating system such as
Unix. While a more traditional language like
C does not support object-orientation as fluidly as more recent languages, the notion of, for example, a
file,
stream, or
device driver (in Unix, each represented as a
file descriptor) can be considered a good example of objects. They are, after all,
abstract data types, with various
methods in the form of
system calls which behavior varies based on the type of object and which implementation details are hidden from the caller.
Object-orientation has been defined as
objects +
inheritance, and inheritance is only one approach to the more general problem of
delegation that occurs in every operating system.[2] Object-orientation has been more widely used in the
user interfaces of operating systems than in their
kernels.
Background
An object is an instance of a class, which provides a certain set of functionalities. Two objects can be differentiated based on the functionalities (or methods) they support. In an operating system context, objects are associated with a resource. Historically, the object-oriented design principles were used in operating systems to provide several protection mechanisms.[1]
Protection mechanisms in an operating system help in providing a clear separation between different user programs. It also protects the operating system from any malicious user program behavior. For example, consider the case of user profiles in an operating system. The user should not have access to resources of another user. The object model deals with these protection issues with each resource acting as an object. Every object can perform only a set of operations. In the context of user profiles, the set of operations is limited by
privilege level of a user.[1]
Present-day operating systems use object-oriented design principles for many components of the system, which includes protection.
Examples
Athene
Athene is an object-based operating system first released in 2000 by Rocklyte Systems.[3][4] The user environment was constructed entirely from objects that are linked together at runtime. Applications for Athene could also be created using this methodology and were commonly scripted using the object scripting language Dynamic Markup Language (DML). Objects could have been shared between processes by creating them in
shared memory and locking them as needed for access. Athene's object framework was multi-platform, allowing it to be used in Windows and Linux environments for developing object-oriented programs. The company went defunct and the project abandoned sometime in 2009.
BeOS
BeOS[5] was an object-oriented operating system released in 1995, which used objects and the
C++ language for the
application programming interface (API). The kernel was written in C with C++ wrappers in user space. The OS did not see mainstream usage and proved commercially unviable, however it has seen continued usage and development by a small enthusiast community.
Choices
Choices is an object-oriented operating system developed at the
University of Illinois at Urbana–Champaign.[6][7] It is written in
C++ and uses objects to represent core kernel components like the
central processing unit (CPU),
processes, and so on.
Inheritance is used to separate the kernel into portable machine-independent classes and small non-portable dependent classes. Choices has been ported to and runs on
SPARC,
x86, and
ARM.
ETHOS
ETHOS was an experimental object oriented version of the Oberon System (see below) created by Clemens Szyperski for his PhD Thesis[8] written in
Oberon-2
GEOS
PC/GEOS is a light-weight object-oriented multitasking graphical operating system with sophisticated window and desktop management featuring scalable fonts. It is mostly written in an object-oriented x86 assembly language dialect and some C/C++ and is designed to run on
DOS (similar to Microsoft Windows up to
Windows Me). GEOS was developed originally by
Berkeley Softworks in 1990, which later became GeoWorks Corporation, and it is continued to be maintained by BreadBox Computer Company. Related
software suites were named Ensemble and New Deal Office. Adaptations exist for various palmtops, and 32-bit systems with non-x86-CPUs.
Haiku
Haiku (originally named OpenBeOS), is an open-source replacement for BeOS. It reached its first development milestone in September 2009 with the release of Haiku R1/Alpha 1. The x86 distribution is compatible with BeOS at both source and binary level. Like BeOS, it is written primarily in
C++ and provides an object-oriented API. It is actively developed.
IBM i (OS/400, i5/OS)
IBM introduced
OS/400 in 1988. This OS ran exclusively on the
AS/400 platform. Renamed
IBM i in 2008, this operating system and runs exclusively on
Power Systems which also can run
AIX and
Linux. IBM i uses an object-oriented methodology and integrates a database (
Db2 for i). The IBM i OS has a 128-bit unique identifier for each object.
IBM OS/2 2.0
IBM's first priority based pre-emptive multitasking, graphical, windows-based operating system included an object-oriented user shell. It was designed for the Intel 80386 that used
virtual 8086 mode with full 32-bit support and was released in 1992.
ArcaOS, a new OS/2 based operating system initially called Blue Lion[9] is being developed by Arca Noae. The first version was released in May 2017.
IBM TopView
TopView was an object-oriented operating environment that loaded on a PC on DOS, and then took control from DOS. At that point it effectively became an object-oriented operating system with an object-oriented API (TopView API). It was IBM's first multi-tasking, window based, object-oriented operating system for the PC led by David C. Morrill and released in February 1985.
Java-based
Given that
Oracle's (formerly
Sun Microsystems')
Java is today one of the most dominant object-oriented languages, it is no surprise that Java-based operating systems have been attempted. In this area, ideally, the
kernel would consist of the bare minimum needed to support a
Java virtual machine (JVM). This is the only component of such an operating system that would have to be written in a language other than Java. Built on the JVM and basic hardware support, it would be possible to write the rest of the operating system in Java; even parts of the system that are more traditionally written in a lower-level language such as C, for example
device drivers, can be written in Java.
Examples of attempts at such an operating system include
JavaOS, JOS,[10] JNode, and
JX.
Xerox developed several workstations with an operating system written in
Interlisp-D. Interlisp-D provided object-oriented extensions like LOOPS and CLOS.
Movitz and
Mezzano are two more recent attempts at operating systems written in Common Lisp.
The
Object Manager is in charge of managing NT objects. As part of this responsibility, it maintains an internal
namespace where various operating system components, device drivers, and
Win32 programs can store and lookup objects. The NT
Native API provides routines that allow
user space (mode) programs to browse the namespace and query the status of objects located there, but the interfaces are undocumented.[16] NT supports per-object (file, function, and role)
access control lists allowing a rich set of security permissions to be applied to systems and services. WinObj is a Windows NT program that uses the NT Native API (provided by NTDLL.DLL) to access and display information on the NT Object Manager's name space.[17]
Object Linking and Embedding (OLE) was part of a grander plan named
Cairo, the code name for a project at Microsoft from 1991 to 1996. Its charter was to build technologies for a next generation operating system that would fulfill
Bill Gates' vision of "information at your fingertips".[18][19] Cairo
never shipped, although parts of its technologies have since appeared in other products. The
Windows 95graphical user interface was based on the initial design work that was done on the Cairo user interface. The remaining component is the
object-based file system. It was once planned to be implemented in the form of Windows Future Storage (
WinFS) as part of
Windows Vista. WinFS is the code name for data storage and
management system project based on
relational databases, running on the Windows NT
file system (
NTFS), which is object-oriented in that it can store the NT objects including its NT object identifier. Each NTFS object has an object identifier; a shortcut with a target that's on an NTFS volume also records the object identifier of the shortcut target, and the object identifier of the drive.[20] WinFS was first demonstrated in 2003 as an advanced storage subsystem for the
Microsoft Windowsoperating system, designed for
persistence and management of
structured,
semi-structured, and
unstructured data. WinFS development was cancelled in June 2006, with some of its technologies merged into other Microsoft products such as
Microsoft SQL Server 2008 and
Microsoft SharePoint. It was subsequently confirmed in an interview with Bill Gates that Microsoft planned to migrate applications like
Windows Media Player,
Windows Photo Gallery,
Microsoft Office Outlook, etc., to use
WinFS as the data storage back-end.[21]
NeXTSTEP
During the late 1980s,
Steve Jobs formed the computer company
NeXT. One of NeXT's first tasks was to design an object-oriented operating system,
NeXTSTEP. They did this by adding an object-oriented framework on
Mach and
BSD using the
Objective-C language as a basis. It achieved a niche status in the computing market, notably used by
Tim Berners-Lee developing the first implementation of the
World Wide Web.
OpenStep was provided as an API layer on many operating systems, namely
HP-UX, NextStep,
Solaris, and Windows.
Oberon System
Oberon System is a single user, object-oriented operating system made for the
Ceres line of
workstations (processor:
National SemiconductorNS32000), developed in the later 1980s at
ETH Zurich by
Niklaus Wirth and
Jürg Gutknecht. It is built entirely from modules of the programming language
Oberon.[22] There are two successors of the Oberon System, ETHOS (see above) and, as of 2023 still maintained, an evolution named Active Object System (AOS),[23] then renamed Bluebottle, then renamed A2.
OOSMOS
The Object-Oriented State Machine Operating System (OOSMOS), written in C, promotes object-oriented encapsulation and implements a full table-driven hierarchical state machine architecture. It generates C code directly from state charts drawn with the open source tool
UMLet. OOSMOS also supports a unique feature call 'state threads' which allows a thread of execution per state. OOSMOS operates on a bare board or in cooperation with an existing operating system.
Phantom OS
Phantom OS adheres to a principle where "everything is an object" and eliminates the concept of a file entirely, instead transparently persisting virtual memory to storage.
ReactOS
ReactOS is an open-source operating system intended to be binary compatible with application software and
device drivers made for Microsoft Windows NT versions. Written from scratch, it aims to follow the
architecture of Windows NT designed by Microsoft from the hardware level right through to the application level. This is not a Linux-based system, and shares none of the
unix architecture.[24][25]
Smalltalk
Smalltalk was invented at
Xerox in the 1970s. The Smalltalk system is fully object-oriented and needs very little support by
BIOS and the
run-time system.
Syllable
Syllable makes heavy use of
C++ and for that reason is often compared to
BeOS.
Taligent was an object-oriented operating system project, begun by
Apple Inc. and jointly developed with
IBM in the 1990s. It was later spun off to an IBM subsidiary and transformed from an operating system to a programming environment.
^Wegner, Peter (December 1987). "Dimensions of Object-based Language Design". ACM SIGPLAN Notices. 22 (12): 168–182.
doi:
10.1145/38807.38823. Also in Conference Proceedings on Object-oriented Programming Systems, Languages.
^"About". JOS (A Free Java-Based Operating System). Retrieved 2012-09-03. The JOS Project is a collaborative undertaking by an international group of Java™ programmers and enthusiasts aimed at the creation of a free and open Java™ based Operating System (JOS). As a collaborative effort, we work together to research how a Java-based operating system should work. Together, we work to build components for a Java-based operating system.
^
Knudsen, Svend Erik (25 October 2000). "Medos in Retrospect". In Böszörményi, László;
Gutknecht, Jürg; Pomberger, Gustav (eds.). The School of Niklaus Wirth: The Art of Simplicity. Morgan Kaufmann. pp. 69–86.
ISBN978-1558607231.
ISBN1-55860-723-4 & dpunkt,
ISBN3-932588-85-1.
^"Object-Based". Microsoft Hardware Development Centre. Retrieved Aug 23, 2015.
^Nebbett, Gary (February 20, 2000). Windows NT/2000 Native API Reference. Sams Publishing. p. 528.
ISBN978-1578701995. The Windows NT/2000 Native API Reference provides the first comprehensive look at these undocumented services. A unique tool for software developers, this reference includes documentation of over 200 routines included in the native API, detailed description of routines that are either not directly accessible via the Win32 API, or that offer substantial additional functionality.
^Russinovich, Mark.
"Windows Sysinternals WinObj". Microsoft. Retrieved 2014-05-16. Obj is a must-have tool if you are a system administrator concerned about security, a developer tracking down object-related problems, or just curious about the Object Manager namespace.
^Gates, Bill (1994).
""Information at Your Fingertips" #2 Keynote (The Road Ahead) – Comdex 1994". Microsoft. Retrieved 2014-05-16. Bill Gates' "Information At Your Fingertips" keynote speech for Comdex 1995 became the basis for his book The Road Ahead, predicting the next decade in technology – right and wrong. These predictions are enlivened by the interaction between Gates speaking and a made-for-Comdex future crime show.
^Chen, Raymond (2007).
"Windows Confidential: The NT Way (excerpts from "The Old New Thing" book)". Microsoft. Retrieved 2014-05-16. The Windows NT file system folks looked at the Windows 95 shortcut resolution algorithm and scoffed. " We can do better than that: We're object-oriented!" Each NTFS object has an object identifier; a shortcut with a target that's on an NTFS volume also records the object identifier of the shortcut target, as well as the object identifier of the drive itself.
^Friedl, Klemens.
"About ReactOS: Object Based". ReactOS Project. Retrieved 2017-02-19. ReactOS uses an object metaphor that is pervasive throughout the architecture of the system. Not only are all of the things in the UNIX file metaphor viewed as objects by ReactOS, but so are things such as processes and threads, shared memory segments, the global registry database and even access rights.
^Filby, J. "ReactOS: An open-source alternative to NT?." IEEE Software 16.1 (1999): 35–35.