Editing Windows NT 3.1 (section)

== Features ==
=== Architecture ===
While Windows NT 3.1 uses the same graphical user interface as Windows 3.1, it was developed anew. The operating system is not DOS-based, but an independent 32-bit operating system; many concepts were taken from Cutler's previous operating system, [[OpenVMS|VMS]].<ref name="russinovich" /> The [[architecture of Windows NT]] takes some ideas of the [[client–server model]], like the modular structure and the communication between the modules.<ref name="Custer1993"/>{{rp|page=20}} System resources like memory, files or devices are viewed as [[Object (computer science)|object]]s by the operating system, which are all accessed in the same way through [[Handle (computing)|handles]] and which can in this way be secured against unauthorized access.<ref name="Custer1993"/>{{rp|pages=22–23}}

The operating system was designed for multiprocessor systems; it supports [[preemptive multitasking]]<ref name="Custer1993"/>{{rp|page=92}} and can make use of [[Thread (computing)|threads]] to run multiple processes in parallel.<ref name="Custer1993"/>{{rp|page=94}} Using [[symmetric multiprocessing]], the processing usage is evenly distributed among all available processors.<ref name="Custer1993"/>{{rp|page=24}} The [[inter-process communication]] in Windows NT 3.1 is designed around networks; two newly introduced functions, [[Remote Procedure Call]] (RPC) and [[Network DDE]], an extension of [[Dynamic Data Exchange]] (DDE), facilitate the access and data exchange between processes running on different computers inside a network.<ref name="PCMag28Sep1993_S211">{{cite journal| last1=Ayre | first1=Rick | last2=Raskin | first2=Robin | title=Windows NT: See how it runs | journal=PC Magazine | volume=12 | issue=16 | date=1993-09-28 | pages=211–231 |issn=0888-8507 | url= https://books.google.com/books?id=5KSmAXszIQYC}}</ref>

The operating system is designed to combine certain elements of a [[monolithic kernel]] and a microkernel;<ref name="Custer1993"/>{{rp|page=20}} nowadays this is most often referred to as a [[hybrid kernel]].<ref name="mskernel">{{cite web |date=February 20, 2014 |title=MS Windows NT Kernel-mode User and GDI White Paper |url=https://technet.microsoft.com/library/cc750820.aspx |access-date=2012-06-07 |website=Microsoft}}</ref> The [[hardware abstraction layer]] represents the lowermost layer and isolates the operating system from the underlying hardware to make it easy to port the operating system to other platforms.<ref name="Custer1993"/>{{rp|page=30}} The kernel running atop only has very basic functions like [[interrupt]] management and processor synchronization. All other functions of the operating system core are handled by modules<ref name="Custer1993"/>{{rp|page=20}} which operate independently from one another and can be swapped without affecting the rest of the operating system.<ref name="Custer1993"/>{{rp|page=28}}

Positioned above the operating system core are the subsystems. There are two types of subsystems: one are the ''integral subsystems'', which perform important operating system functions. One such subsystem is the security subsystem, which handles the logon process and monitors the security of the system. The other type of subsystem is the ''environment subsystem'', which exposes the operating system functions to applications via [[application programming interface]]s.<ref name="Custer1993"/>{{rp|page=27}} The base subsystem is the 32-bit subsystem which runs 32-bit applications written for Windows NT. Windows NT applications can only run on one platform, and must be recompiled for every platform. The 32-bit subsystem also contains all [[output (computing)|output]] functions, including the [[Graphics Device Interface]] (GDI),<ref name="ct1993">{{cite journal | last=Siering | first=Peter | title=Paarige Premiere: Microsoft Windows NT 3.1 und Advanced Server | journal=C't | issue=11 | year=1993 | pages=142 ff}}</ref> so all other subsystems have to call the 32-bit subsystem to be able to output text or graphics.<ref name="Custer1993"/>{{rp|page=33}} Other subsystems contained in Windows NT 3.1 are the POSIX subsystem, which supports POSIX-compatible applications built for Windows NT, and, in the x86 version only, the OS/2 subsystem, which allows command-line based OS/2 1.x applications to run.<ref name="ct1993" />

The [[Virtual DOS Machine]] (VDM) is sometimes also viewed as a subsystem, but is, strictly speaking, a normal 32-bit Windows application. It manages applications originally built for DOS. Built on top is [[Windows on Windows]] (WoW), which allows applications built for 16-bit Windows operating systems like Windows 3.1 to run. On x86 computers, the virtual DOS machine uses the [[virtual 8086 mode]] to run DOS applications directly,<ref name="ct1993" /> on RISC computers, an emulator licensed from ''Insignia Solutions'' is used which emulates a [[80286]] processor. However, not all DOS and 16-bit Windows applications can be run on Windows NT 3.1 due to various limitations,<ref name="ct1994">{{cite journal |last=Siering |first=Peter |year=1994 |title=Lizenz-Rezepte: Windows NT 3.5 Workstation und Server |journal=C't – Magazin für Computertechnik |issue=12 |pages=266}}</ref> one of them being the inability of applications to directly access the hardware. As well, [[VxD]] files sometimes needed by applications cannot be used with Windows NT 3.1.<ref name="msq103012">{{Cite web|url=http://support.microsoft.com/kb/103012/en-us|title=Virtual Device Drivers (VXDs) Do Not Work in Windows NT|date=April 8, 2004|website=Microsoft Support|archive-url=https://web.archive.org/web/20130227071247/http://support.microsoft.com/kb/103012/en-us|archive-date=February 27, 2013|access-date=May 9, 2019}}</ref> While pure DOS applications are run in separate memory spaces, 16-bit Windows applications have to share one memory space. While this is done due to compatibility reasons with applications which depend on this ability, like [[Schedule+]] and [[Microsoft Mail]], it also means that 16-bit Windows applications only run in [[cooperative multitasking]]. A faulty 16-bit Windows application is in this way able to cause all other 16-bit Windows applications (but not Windows NT itself) to crash.<ref name="ct1993" />

[[Image:NT 3.1 layers.png|thumb|center|600px|Graphical view of the architecture of Windows NT 3.1. Shown are the following components of the operating system core: I/O Manager, Object Manager, Security Reference Monitor, Process Manager, Local Procedure Call Facility, Virtual Memory Manager.<ref name="Custer1993"/>{{rp|pages=26–33}}]]

=== System ===
Windows NT 3.1 provides a [[boot manager]] called [[NTLDR]] which is loaded during the startup process of the operating system on x86-based computers. It allows a multiboot setup of multiple instances of Windows NT 3.1, as well as MS-DOS and OS/2 1.x.<ref name="msq106168">{{Cite FTP | title=Microsoft Knowledge Base – Windows NT Multi-Boot Support Limitations | url=ftp://ftp.microsoft.com/MISC1/BUSSYS/WINNT/KB/Q106/1/68.TXT | server=FTP server | url-status=dead | access-date=2012-06-08 }}</ref> NTLDR is not used for the RISC versions because the RISC computers' firmware provides their own boot manager.<ref name="msstartup">{{cite web | title=Windows NT Resource Kit – Chapter 19 – What Happens When You Start Your Computer| url=https://technet.microsoft.com/en-us/library/cc750074 | access-date= 2012-06-08}}</ref>

Every user has to log on to the computer after Windows NT 3.1 is booted up by pressing the key combination [[Control-Alt-Delete|Ctrl+Alt+Del]] and entering the user name and password. All users have their own [[user account]], and user-specific settings like the [[Program Manager]] groups are stored separately for every user. Users can be assigned specific rights, like the right to change the system time or the right to shut down the computer. To facilitate management of user accounts, it is also possible to group multiple user accounts and assign rights to groups of users.<ref name="ct1993" />

Windows NT 3.1 introduced the new [[NTFS]] file system. This new file system is more robust against hardware failures<ref name="Custer1993"/>{{rp|page=10}} and allows assignment of read and write rights to users or groups on the file system level.<ref name="ct1993" /> NTFS supports long file names<ref name="ct1993" /> and has features to accommodate POSIX applications like [[hard link]]s.<ref name="Custer1993"/>{{rp|page=39}} For compatibility reasons, Windows NT 3.1 also supports [[FAT16]] as well as OS/2's file system [[High Performance File System|HPFS]],<ref name="ct1993" /> but does not support long file names on FAT file system ([[VFAT]]). This was added in Windows NT 3.5.

Designed as a networking operating system, Windows NT 3.1 supports multiple [[network protocol]]s. Besides [[IPX/SPX]] and [[NetBEUI]], the [[TCP/IP]] protocol is supported allowing access to the Internet.<ref name="ct1993" /> Similar to ''Windows for Workgroups'', files and printers can be shared and the access rights and configuration of these resources can be edited over the network. When a network printer is installed, the required drivers are automatically transferred over the network, removing the need to manually install the drivers for every computer.<ref name="ct1993" /> The [[Remote Access Service]] (RAS) allows a client from outside the network to connect to the network using a [[modem]], [[ISDN]] or [[X.25]] and access its resources. While the workstation allows one RAS connection at a time, the server supports 64.<ref name="ct1993" />

Windows NT 3.1 supports the then-new [[Unicode]] standard, a [[character set]] which allows multiple languages to be displayed. This facilitates [[Internationalization and localization|localization]] of the operating system.<ref name="msq99884">{{Cite web |date=November 4, 2003 |title=Unicode and Microsoft Windows NT |url=http://support.microsoft.com/kb/99884/EN-US/ |archive-url=https://web.archive.org/web/20041205100017/http://support.microsoft.com/kb/99884/EN-US/ |archive-date=December 5, 2004 |access-date=May 9, 2019 |website=Microsoft Support}}</ref> All strings, as well as file and folder names, are internally processed in Unicode,<ref name="Custer1993"/>{{rp|page=43}} but the included programs, like the [[File Manager]], are not Unicode aware, so folders containing Unicode characters cannot be accessed.<ref name="msq102384">{{Cite web|url=http://support.microsoft.com/kb/102384/en-us|title=Windows NT File Manager: Services for Macintosh Concerns|date=October 31, 2006|website=Microsoft Support|archive-url=https://web.archive.org/web/20130227071307/http://support.microsoft.com/kb/102384/en-us|archive-date=February 27, 2013|access-date=May 9, 2019}}</ref> For demonstration purposes, a [[Unicode typeface]] called ''[[Lucida]] Sans Unicode'' is shipped with Windows NT 3.1<ref name="bigelow">{{cite journal | last1=Bigelow | first1=Charles | last2=Holmes | first2=Kris | title=The design of a Unicode font | journal=Electronic Publishing | volume=6 | issue=3 | date=September 1993 | pages=289–305 | url= http://cajun.cs.nott.ac.uk/wiley/journals/epobetan/pdf/volume6/issue3/bigelow.pdf | format=PDF; 0,5 MB |issn=0894-3982}}</ref> even though it is not installed by default. The previous [[code page]]s are still supported for compatibility purposes.<ref name="msq99884" />

The [[Windows registry]], introduced with Windows 3.1, is a central, hierarchical configuration database<ref name="ct1993" /> designed to allow configuration of computers over the network<ref name="ZacharyShowstopper"/>{{rp|page=251}} and to replace the commonly-used text-based configuration files, like [[INI file]]s, [[AUTOEXEC.BAT]] and [[CONFIG.SYS]].<ref name="Custer1993"/>{{rp|page=327}} Using the undocumented registry editor, the Windows registry can be viewed and edited by the user.<ref name="ct1993" />

The ''Advanced Server'' is designed to manage the workstation computers.<ref  name="ct1993" /> It can function as a [[Domain controller]], where all users and groups as well as their rights are stored. This way, a user can log on from any computer in the network, and users can be managed centrally on the server. Trust relationships can be built to other domains to be able to exchange data cross-domain.<ref name="ct1993" /> Using the [[Replication (computing)|replication]] service, files like logon scripts can be synchronized across all computers on the network. The Advanced Server supports the [[AppleTalk]] protocol to allow connections to Macintosh computers.<ref name="ct1993" /> Hard drives can be combined to [[RAID]]s in Windows NT 3.1 Advanced Server, the supported configurations are RAID 0, RAID 1 and RAID 5.

=== Included programs ===
Windows NT 3.1, for the most part, comes with 32-bit versions of the components featured in Windows 3.1 and Windows for Workgroups. However, it also included applications specifically aimed at the needs of Windows NT, like the User Manager, the [[Performance Monitor]], the Disk Administrator, the [[Event Viewer]] and the ''Backup'' application. The ''Advanced Server'' contained further, server-specific administration tools. Because Windows NT 3.1 is not DOS-based, a new 32-bit command-line processor, called [[CMD.EXE]] was included which was compatible with MS-DOS 5.0.<ref name="ct1993" /> For compatibility reasons, Windows NT 3.1 shipped with a few 16-bit applications, like [[Microsoft Write]] or [[EDLIN]].<ref name="msq101929">{{Cite web|url=http://support.microsoft.com/kb/101929/en-us|title=16-Bit Applications Included with Windows NT|date=October 31, 2006|website=Microsoft Support|archive-url=https://web.archive.org/web/20130227071235/http://support.microsoft.com/kb/101929/en-us|archive-date=February 27, 2013|access-date=May 9, 2019}}</ref>

Windows NT 3.1, being an all-new operating system for which no previous MS-DOS based drivers could be used, includes a wealth of drivers for various common components and peripherals.<ref name="ct1994" /> This includes common [[SCSI]] devices like hard drives, CD-ROM drives, [[tape drive]]s and [[image scanner]]s,<ref name="msq103284">{{Cite web|url=http://support.microsoft.com/kb/103284|title=Contents of Windows NT SETUP.TXT, Part 1|date=October 31, 2006|website=Microsoft Support|archive-url=https://web.archive.org/web/20091031110903/http://support.microsoft.com/kb/103284|archive-date=October 31, 2009|access-date=May 9, 2019}}</ref> as well as [[Industry Standard Architecture|ISA]] devices like graphics cards, sound cards and network cards. The [[EISA bus|EISA]] bus, is supported by Windows NT 3.1. The [[Conventional PCI|PCI bus]], however, is not supported by kernel, but supported by third-party drivers.<ref name="msq113345">{{Cite web|url=http://support.microsoft.com/kb/113345/en-us|title=Support for PCI Computers and Peripherals in Windows NT 3.1|date=October 31, 2006|website=Microsoft Support|archive-url=https://web.archive.org/web/20130227071227/http://support.microsoft.com/kb/113345/en-us|archive-date=February 27, 2013|access-date=May 9, 2019}}</ref> Windows NT 3.1 supports an [[uninterruptible power supply]].<ref name="Custer1993"/>{{rp|page=328}}

Windows NT 3.1 could be installed either by using the CD-ROM and a provided [[boot disk]], or by utilizing a set of twenty-two 3.5" floppies (twenty-three floppies for ''Advanced Server''). Windows NT 3.1 could also be installed over the network.<ref name="ct1993" /> A coupon was included that made it possible to order a set of twenty-seven 5.25" floppies (or twenty-eight floppies for ''Advanced Server'').<ref name="computinghistory">{{cite web |title=Microsoft Windows NT version 3.1 |url=http://www.computinghistory.org.uk/det/12535/Microsoft-Windows-NT-version-3-1/ |access-date=2012-09-06 |website=Centre for Computing History}}</ref> Compared to the floppies, the CD-ROM contained additional drivers and applications.

Windows NT 3.1 does not support [[ATAPI]] CD-ROMs.