Editing Drive letter assignment

{{Short description|Alphabetical assignment to logical drives on computers (e.g., C:\)}}
{{Use dmy dates|date=April 2019|cs1-dates=y}}
[[File:StartingMsdos.png|thumb|[[MS-DOS]] command prompt with drive letter ''C'' as part of the current [[working directory]].]]
[[File:WinFile 10.0 Screen.PNG|thumb|[[File Manager (Windows)|File Manager]] displaying the contents of drive ''C''.]]
In [[computer data storage]], '''drive letter assignment''' is the process of assigning alphabetical identifiers to [[volume (computing)|volumes]]. Unlike the concept of [[Unix filesystem|UNIX]] [[mount point]]s, where volumes are named and located arbitrarily in a single hierarchical namespace, drive letter assignment allows multiple highest-level namespaces. Drive letter assignment is thus a process of using letters to name the roots of the "forest" representing the file system; each volume holds an independent "tree" (or, for non-hierarchical file systems, an independent list of files).

==Origin==
The concept of drive letters, as used today, presumably{{citation needed|date=August 2016}} owes its origins to [[IBM]]'s [[VM (operating system)|VM]] family of operating systems, dating back to [[CP/CMS]] in 1967 (and its research predecessor [[CP-40]]), by way of [[Digital Research]]'s (DRI) [[CP/M]]. The concept evolved through several steps:

* CP/CMS uses drive letters to identify ''[[minidisk (CMS)|minidisk]]s'' attached to a user session.<ref name="ducharme"/> A full file reference (''pathname'' in today's parlance) consists of a ''filename'', a ''filetype'', and a disk letter called a ''filemode'' (e.g. '''A''' or '''B'''). Minidisks can correspond to physical disk drives, but more typically refer to logical drives, which are mapped automatically onto shared devices by the operating system as sets of ''virtual cylinders''.
* CP/CMS inspired numerous other operating systems, including the CP/M microcomputer operating system, which uses a drive letter to specify a physical storage device. Early versions of CP/M (and other microcomputer operating systems) implemented a [[flat file system]] on each disk drive, where a complete file reference consists of a ''drive letter'', a colon, a ''filename'' (up to [[8.3 filename|eight characters]]), a dot, and a ''[[Filename extension|filetype]]'' (three characters); for instance <code>A:README.TXT</code>. (This was the era of [[8-inch floppy disk]]s, where such small namespaces did not impose practical constraints.)  This usage was influenced by the device prefixes used in [[Digital Equipment Corporation]]'s (DEC) [[TOPS-10]] operating system.<ref name="johnson"/>
* The drive letter syntax chosen for CP/M was inherited by [[Microsoft]] for its operating system [[MS-DOS]] by way of [[Seattle Computer Products]]' (SCP) [[86-DOS]], and thus also by IBM's OEM version [[PC&nbsp;DOS]]. Originally, drive letters always represented physical volumes, but support for [[logical volume]]s eventually appeared.
* Through their designated position as DOS successor, the concept of drive letters was also inherited by [[OS/2]] and the [[Microsoft Windows]] family.

The important capability of [[file directory|hierarchical directories]] within each drive letter was initially absent from these systems. This was a major feature of [[UNIX]] and other similar operating systems, where hard disk drives held thousands (rather than tens or hundreds) of files. Increasing microcomputer storage capacities led to their introduction, eventually followed by [[long filename]]s. In file systems lacking such naming mechanisms, drive letter assignment proved a useful, simple organizing principle.

==Operating systems that use drive letter assignment==
{{Expand list|date=November 2010}}

{{div col}}
* CP/M family
** [[CP/M]], [[MP/M]], [[Concurrent CP/M]], [[Concurrent DOS]], [[FlexOS]], [[4680 OS]], [[4690 OS]], [[S5-DOS/MT]], [[Multiuser DOS]], [[Datapac System Manager|System Manager]], [[REAL/32]], [[REAL/NG]], [[Personal CP/M]], [[S5-DOS]], [[DOS Plus]]
* [[AMSDOS]]
* DOS family
** [[86-DOS]], [[MS-DOS]], [[PC&nbsp;DOS]]
** [[DR&nbsp;DOS]], [[Novell DOS]], [[PalmDOS]], [[OpenDOS]]
** [[ROM-DOS]]
** [[PTS-DOS]], [[S/DOS]]
** [[FreeDOS]]
** [[PC-MOS/386]]
** [[SISNE plus]]
* [[GEMDOS]], [[Atari TOS|TOS]], [[MiNT]], [[MagiC]], [[MultiTOS]], [[EmuTOS]]
* [[Atari DOS]] family
* [[MSX-DOS]]
* [[ANDOS]], [[CSI-DOS]], [[MK-DOS]]
* [[GEOS (8-bit operating system)|GEOS]]<ref name="GEOS"/>
* [[OS/2]] (including [[eComStation]] and [[ArcaOS]])
* Windows family
** [[Windows 9x]] family
** [[Windows NT]] family
** [[Xbox system software]]
** [[ReactOS]]
* [[Symbian OS]]
* [[Hobbyist operating system]]s
** [[SymbOS]]
** [[TempleOS]]
{{div col end}}

==Order of assignment==
{{refimprove section|date=February 2011}}
MS-DOS/PC&nbsp;DOS since version 5.0, and later operating systems, assigns drive letters according to the following algorithm:<ref>{{Cite web|date=1996-04-17|title=Order in Which MS-DOS and Windows Assign Drive Letters|url=http://support.microsoft.com/support/kb/articles/q51/9/78.asp|url-status=dead|archive-url=https://web.archive.org/web/19990218071811/http://support.microsoft.com/support/kb/articles/q51/9/78.asp|archive-date=1999-02-18|access-date=2021-01-06|website=Support Online from Microsoft Technical Support|publisher=[[Microsoft]]}}</ref>

# Assign the drive letter '''A:''' to the first [[floppy disk drive]] (drive 0), and '''B:''' to the second floppy disk drive (drive 1). If only one physical floppy is present, drive '''B:''' will be assigned to a phantom floppy drive mapped to the same physical drive and dynamically assigned to either A: or B: for easier floppy file operations. If no physical floppy drive is present, DOS 4.0 will assign both '''A:''' and '''B:''' to the non-existent drive, whereas DOS 5.0 and higher will invalidate these drive letters. If more than two physical floppy drives are present, DOS versions prior to 5.0 will assign subsequent drive letters, whereas DOS 5.0 and higher will remap these drives to higher drive letters at a later stage; see below.
# Assign a drive letter to the first active primary [[Disk partitioning|partition]] recognized upon the first physical [[hard disk]]. DOS 5.0 and higher will ensure that it will become drive '''C:''', so that the boot drive will either have drive '''A:''' or '''C:'''.
# Assign subsequent drive letters to the first primary partition upon each successive physical hard disk drive (DOS versions prior to 5.0 will probe for only two physical hard disks, whereas DOS 5.0 and higher support eight physical hard disks).
# Assign subsequent drive letters to every recognized logical partition present in the first extended partition, beginning with the first hard drive and proceeding through successive physical hard disk drives.
# DOS 5.0 and higher: Assign drive letters to all remaining primary partitions, beginning with the first hard drive and proceeding through successive physical hard disk drives.
# DOS 5.0 and higher: Assign drive letters to all physical floppy drives beyond the second physical floppy drive.
# Assign subsequent drive letters to any block device drivers loaded in [[CONFIG.SYS]] via [[DEVICE (CONFIG.SYS directive)|DEVICE statement]]s, e.g. [[RAM disk]]s.
# Assign subsequent drive letters to any dynamically loaded drives via CONFIG.SYS [[INSTALL (CONFIG.SYS directive)|INSTALL statement]]s, in [[AUTOEXEC.BAT]] or later, i.e. additional [[optical disc drive]]s ([[MSCDEX]] etc.), [[PCMCIA (card)|PCMCIA]] / [[PC Card]] drives, USB or Firewire drives, or [[network drive]]s.

* Only partitions of recognized [[partition type]]s are assigned letters. In particular, "hidden partitions" (those with their type ID changed to an unrecognized value, usually by adding <code>10h</code>) are not.

MS-DOS/PC&nbsp;DOS versions 4.0 and earlier assign letters to all of the floppy drives before considering hard drives, so a system with four floppy drives would call the first hard drive '''E:'''. Starting with DOS 5.0, the system ensures that drive '''C:''' is always a hard disk, even if the system has more than two physical floppy drives.

While without deliberate remapping, the drive letter assignments are typically fixed until the next reboot, however, [[Zenith MS-DOS 3.21]] will update the drive letter assignments when resetting a drive. This may cause drive letters to change without reboot if the partitioning of the harddisk was changed.

MS-DOS on the [[Apricot PC]] assigns letters to hard drives, starting with '''A:''', before considering floppy drives. A system with two of each drive would call the hard drives '''A:''' and '''B:''', and the floppies '''C:''' and '''D:'''.

On the Japanese [[PC-98]], if the system is booted from floppy disk, the dedicated version of MS-DOS assigns letters to all floppy drives before considering hard drives; it does the opposite if it is booted from a hard drive, that is, if the OS was installed on the hard drive, MS-DOS would assign this drive as drive "A:" and a potentially existing floppy as drive "B:". The Japanese version of the [[Windows 95]] SETUP program supports a special option <kbd>/AT</kbd> to enforce that Windows will be on drive C:.

Some versions of DOS do not assign the drive letter, beginning with '''C:''', to the first active primary partition recognized upon the first physical hard disk, but on the first primary partition recognized of the first hard disk, even if it is not set active.

If there is more than one extended partition in a partition table, only the logical drives in the first recognized extended partition type are processed.

Some late versions of the DR-DOS IBMBIO.COM provide a preboot config structure, holding bit flags to select (beside others) between various drive letter assignment strategies. These strategies can be preselected by a user or OEM or be changed by a boot loader on the fly when launching DR-DOS. Under these issues, the boot drive can be different from '''A:''' or '''C:''' as well.

The drive letter order can depend on whether a given disk is managed by a boot-time driver or by a dynamically loaded driver. For example, if the second or third hard disk is of SCSI type and, on DOS, requires drivers loaded through the [[CONFIG.SYS]] file (e.g. the controller card does not offer on-board BIOS or using this BIOS is not practical), then the first SCSI primary partition will appear after all the IDE partitions on DOS. Therefore, DOS and for example OS/2 could have different drive letters, as OS/2 loads the SCSI driver earlier. A solution was not to use primary partitions on such hard disks.

In [[Windows NT]] and [[OS/2]], the operating system uses the aforementioned algorithm to automatically assign letters to [[floppy disk drive]]s, [[optical disc drive]]s, the [[boot disk]], and other recognized volumes that are not otherwise created by an [[System administrator|administrator]] within the operating system. Volumes that are created within the operating system are manually specified, and some of the automatic drive letters can be changed. Unrecognized volumes are not assigned letters, and are usually left untouched by the operating system.

A common problem that occurs with the drive letter assignment is that the letter assigned to a network drive can interfere with the letter of a [[local volume]] (like a newly installed CD/DVD drive or a USB stick). For example, if the last local drive is drive '''D:''' and a network drive would have been assigned as '''E:''', then a newly attached USB mass storage device would also be assigned drive '''E:''' causing loss of connectivity with either the network share or the USB device. Users with administrative privileges can assign drive letters manually to overcome this problem.<ref name="Microsoft_Driveletter"/>
Another condition that can cause problems on [[Windows XP]] is when there are network drives defined, but in an error condition (as they would be on a laptop operating outside the network). Even when the unconnected network drive is not the next available drive letter, Windows XP may be unable to map a drive and this error may also prevent the mounting of the USB device.{{Citation needed|date=December 2010}}

== {{anchor|Memory drive}}Common assignments ==
Applying the scheme discussed above on a fairly modern Windows-based system typically results in the following drive letter assignments:
*'''A:''' — [[Floppy disk drive]]s, {{frac|3|1|2}}″ or {{frac|5|1|4}}″, and possibly other types of disk drives, if present.
*'''B:''' — Reserved for a second floppy drive (that was present on many PCs).
*'''C:''' — First [[hard disk drive]] partition.
*'''D:''' to '''Z:''' — Other disk partitions get labeled here. Windows assigns the next free drive letter to the next drive it encounters while enumerating the disk drives on the system. Drives can be partitioned, thereby creating more drive letters. This applies to MS-DOS, as well as all Windows operating systems. Windows offers other ways to change the drive letters, either through the Disk Management snap-in or <code>[[diskpart]]</code>. MS-DOS typically uses parameters on the line loading device drivers inside the [[CONFIG.SYS]] file.
Case-specific drive letters:
*'''F:''' — First network drive if using [[Novell NetWare]].
*'''G:''' — "Google Drive File Stream" if using [[Google Drive]].
*'''H:''' — "Home" directory on a network server.
*'''L:''' — Dynamically assigned [[load drive]] under Concurrent DOS, Multiuser DOS, System Manager and REAL/32.<ref name="DRI_1987_CDOS_User"/><ref name="DRI_1987_CDOS"/>
*'''M:''' — Drive letter for optionally [[memory drive]] MDISK under Concurrent DOS.<!-- possibly also in Multiuser DOS, System Manager and REAL/32? --><ref name="DRI_1987_CDOS_User"/>
*'''N:''', '''O:''', '''P:''' — Assignable [[floating drive]]s under CP/M-86 4.x, Personal CP/M-86 2.x, [[DOS Plus]] 1.1-2.1 (via BDOS call 0Fh), a concept later extended to any unused drive letters under Concurrent DOS, Multiuser DOS, System Manager, REAL/32 and DR DOS up to 6.0.<ref name="DRI_1987_CDOS_User"/><ref name="DRI_1987_CDOS"/>
*'''Q:''' — Microsoft Office Click-to-Run virtualization.
*'''U:''' — Unix-like ''unified filesystem'' with virtual directory <code>\DEV</code> for [[device file]]s under [[MiNT]], [[MagiC]], and [[MultiTOS]].<ref name="MagiC_2016_DriveU"/><ref name="FreeMiNT_2000"/>
*'''Z:''' — First network drive if using [[Banyan VINES]], and the initial drive letter assignment for the virtual disk network in the [[DOSBox]] [[x86]] emulator. It is also the first letter selected by Windows for network resources, as it automatically selects from '''Z:''' downwards. By default, [[Wine (software)|Wine]] maps '''Z:''' to the root of the UNIX directory tree.<ref name="Wine"/>

When there is no second physical floppy drive, drive '''B:''' can be used as a "virtual" floppy drive mapped onto the physical drive '''A:''', whereby the user would be prompted to switch floppies every time a read or write was required to whichever was the least recently used of '''A:''' or '''B:'''. This allows for much of the functionality of two floppy drives on a computer that has only one. This concept of multiple drive letters sharing a single physical device (optionally with different "views" of it) is not limited to the first floppy drive, but can be utilized for other drives as well by setting up additional block devices for them with the standard DOS [[DRIVER.SYS]] in [[CONFIG.SYS]].

Network drives are often assigned letters towards the end of the alphabet. This is often done to differentiate them from local drives: by using letters towards the end, it reduces the risk of an assignment conflict. It is especially true when the assignment is done automatically across a network (usually by a logon script).

In most DOS systems, it is not possible to have more than 26 mounted drives. Atari GEMDOS supports 16 drive letters '''A:''' to '''P:''' only. The PalmDOS PCMCIA driver stack supports drive letters '''0:''', '''1:''', '''2:''', ... to address PCMCIA drive slots.

Some Novell network drivers for DOS support up to 32 drive letters under compatible DOS versions. In addition, Novell DOS 7, OpenDOS 7.01, and DR-DOS 7.02 genuinely support a CONFIG.SYS <code>[[LASTDRIVE (CONFIG.SYS directive)|LASTDRIVE]]=32</code> directive in order to allocate up to 32 drive letters, named '''A:''' to '''Z:''', '''[:''', '''\:''', ''']:''', '''^:''', '''_:''' and '''`:'''. (DR-DOS 7.02-7.07 also supports <code>HILASTDRIVE</code> and <code>LASTDRIVEHIGH</code> directives in order to relocate drive structures into upper memory.) Some DOS application programs do not expect drive letters beyond '''Z:''' and will not work with them, therefore it is recommended to use them for special purposes or search drives.

JP Software's [[4DOS]] command line processor supports drive letters beyond '''Z:''' in general, but since some of the letters clash with syntactical extensions of this command line processor, they need to be escaped in order to use them as drive letters.

Windows 9x (MS-DOS 7.0/MS-DOS 7.1) added support for <code>LASTDRIVE=32</code> and <code>LASTDRIVEHIGH=32</code> as well.

If access to more filesystems than '''Z:''' is required under Windows NT, [[Volume Mount Point]]s must be used.<ref name="Microsoft_Server"/> However, it is possible to mount non-letter drives, such as '''1:''', '''2:''', or '''!:''' using the command line <code>[[SUBST]]</code> utility in Windows XP or later (i.e. <code>SUBST 1: C:\TEMP</code>), but it is not officially supported and may break programs that assume that all drives are letters '''A:''' to '''Z:'''.

=={{anchor|Floating drive|Load drive}}ASSIGN, JOIN and SUBST in DOS and Windows==
Drive letters are not the only way of accessing different volumes. [[DOS]] offers a [[JOIN (DOS command)|JOIN]] command that allows access to an assigned volume through an arbitrary directory, similar to the [[Unix]] ''[[mount (Unix)|mount]]'' command. It also offers a [[SUBST]] command which allows the assignment of a drive letter to a directory. One or both of these commands were removed in later systems like [[OS/2]] or [[Windows NT]], but starting with [[Windows 2000]], both are again supported: The SUBST command exists as before, while JOIN's functionality is subsumed in [[LINKD]] (part of the Windows [[Resource Kit]]). In [[Windows Vista]], the new command [[MKLINK]] can be used for this purpose. Also, Windows 2000 and later support mount points, accessible from the [[Control Panel (Windows)|Control Panel]].

Many operating systems originating from Digital Research provide means to implicitly assign substitute drives, called ''floating drives'' in DRI terminology, by using the CD/CHDIR command in the following syntax:

 CD N:=C:\SUBDIR

[[DOS Plus]]<!-- perhaps Concurrent CP/M-86 as well? --> supports this for drive letters '''N:''', '''O:''', and '''P:'''. This feature is also present in [[Concurrent DOS]]<!-- at least in Concurrent DOS XM and Concurrent DOS 386 since 1987 -->, <!-- perhaps FlexOS as well? -->[[Multiuser DOS]], System Manager 7, and [[REAL/32]], however, these systems extend the concept to all unused drive letters from A: to Z:, except for the reserved drive letter L:.<ref name="DRI_1987_CDOS"/> [[DR DOS]] 3.31 - 6.0 (up to the 1992-11 updates with BDOS 6.7 only<!-- BDOS 7.0 (PalmDOS), BDOS 7.1 (DR DOS 6.0 business update 1993) and higher no longer support this -->) also supports this including drive letter L:. This feature is not available under DR DOS 6.0 (1992 upgrade), PalmDOS 1.0, Novell DOS 7, OpenDOS 7.01, DR-DOS 7.02 and higher. Floating drives are implemented in the BDOS kernel, not in the command line shell, thus they can be used and assigned also from within applications when they use the "change directory" system call. However, most DOS applications are not aware of this extension and will consequently discard such directory paths as invalid. JP Software's command line interpreter 4DOS supports floating drives on operating systems also supporting it.

In a similar feature,<!-- not sure about DOS Plus!--> Concurrent DOS<!-- at least Concurrent DOS XM and Concurrent DOS 386 since 1987 -->, Multiuser DOS, System Manager and REAL/32 will dynamically assign a drive letter '''L:''' to the load path of a loaded application, thereby allowing applications to refer to files residing in their load directory under a standardized drive letter instead of under an absolute path.<ref name="DRI_1987_CDOS"/> This [[load drive]] feature makes it easier to move software installations on and across disks without having to adapt paths to overlays, configuration files or user data stored in the load directory or subsequent directories.
(For similar reasons, the appendage to the environment block associated with loaded applications under DOS 3.0 (and higher) contains a reference to the load path of the executable as well, however, this consumes more resident memory, and to take advantage of it, support for it must be coded into the executable, whereas DRI's solution works with any kind of applications and is fully transparent to users as well.)
In some versions of DR-DOS, the load path contained in the appendage to the environment passed to drivers can be shortened to that of a temporary substitute drive (e.g. <code>SUBST B: C:\DIR</code>) through the <code>[[INSTALL (CONFIG.SYS directive)|INSTALL[HIGH]]]</code>/<code>[[LOADHIGH]]</code> option <code>/D[:loaddrive]</code> (for <code>B:TSR.COM</code> instead of, say, <code>C:\DIR\TSR.COM</code>). This can be used to minimize a driver's effective [[memory footprint]], if the executable is located in a deep subdirectory and the resident driver happens to not need its load path after installation any more.<ref name="Paul_1997_OD-A3"/><ref name="Paul_1997_NWDOSTIP"/><ref name="Paul_1997_SETENV"/><ref name="Paul_2002_COM"/>

==See also==
* [[Drive mapping]]
* [[Filename]]
* [[net (command)]], a command in Microsoft Windows that can be used for viewing/controlling drive-letter assignments for network drives
* [[Portable application]]

==References==
{{Reflist|refs=
<ref name="ducharme">{{cite book |author-last=DuCharme |author-first=Bob |title=The Operating System Handbook, or, Fake Your Way Through Minis and Mainframes |date=2001 |chapter=VM/CMS |chapter-url=http://www.snee.com/bob/opsys/part5vmcms.pdf}}</ref>
<ref name="johnson">{{cite web |title=CP/M and Digital Research Inc. (DRI) History |author-last=Johnson |author-first=Herbert R. |date=2009-01-04 |work=www.retrotechnology.com |url=http://www.retrotechnology.com/dri/d_dri_history.html |access-date=2009-01-28}}</ref>
<ref name="GEOS">{{cite web |title=GEOS |url=http://osnews.com/story/15223/GEOS_The_Graphical_Environment_Operating_System/page7/}}</ref>

<!-- Not in use
<ref name="DexOS">{{cite web |title=DexOS |url=http://www.dex-os.com/old/dosbox.htm |access-date=24 February 2012 |archive-url=https://web.archive.org/web/20160303235911/http://www.dex-os.com/old/dosbox.htm |archive-date=3 March 2016 |url-status=dead }}</ref>
Not in use-->

<ref name="Microsoft_Driveletter">{{cite web |title=Change a drive letter |publisher=[[Microsoft]] |url=https://docs.microsoft.com/en-us/windows-server/storage/disk-management/change-a-drive-letter |access-date=2019-03-04}}</ref>
<ref name="DRI_1987_CDOS_User">{{cite book |title=Concurrent DOS 386 - Multiuser/Multitasking Operating System - User Guide |publisher=[[Digital Research]] |url=http://bitsavers.org/pdf/digitalResearch/concurrent/1126-2004-001_Concurrent_DOS_386_Users_Guide_Nov87.pdf}}</ref>
<ref name="MagiC_2016_DriveU">{{cite web |title=The drive U: in MagiC |date=2016-03-28 |url=http://toshyp.atari.org/en/00b00b.html |access-date=2017-01-09 |url-status=live |archive-url=https://web.archive.org/web/20170115164938/http://toshyp.atari.org/en/00b00b.html |archive-date=2017-01-15}}</ref>
<ref name="FreeMiNT_2000">{{cite web |title=FreeMiNT-Portal - mint.doc |date=2000-04-27 |url=http://freemint.de/docs/mint.mint_doc.html |access-date=2017-01-09 |url-status=live |archive-url=https://web.archive.org/web/20170115165043/http://freemint.de/docs/mint.mint_doc.html |archive-date=2017-01-15}}</ref>
<ref name="Wine">{{Cite web |title=Wine FAQ |url=https://wiki.winehq.org/FAQ#Is_Wine_malware-compatible.3F}}</ref>
<ref name="Microsoft_Server">{{cite web |title=simple volumes |publisher=[[Microsoft TechNet]] |url=http://technet2.microsoft.com/WindowsServer/en/library/f7e61105-8033-4c45-a6d2-9476266aac221033.mspx?mfr=true |access-date=2006-12-01 |archive-url=https://web.archive.org/web/20070326145909/http://technet2.microsoft.com/WindowsServer/en/library/f7e61105-8033-4c45-a6d2-9476266aac221033.mspx?mfr=true |archive-date=2007-03-26}}</ref>
<ref name="DRI_1987_CDOS">{{cite book |publisher=[[Digital Research]] |title=Concurrent DOS 386 - Multiuser/Multitasking Operating System - Reference Manual |date=1987 |url=http://bitsavers.trailing-edge.com/pdf/digitalResearch/concurrent/1126-2064-001_Concurrent_DOS_386_Reference_Guide_Nov87.pdf}}</ref>
<ref name="Paul_1997_OD-A3">{{cite web |author-first=Matthias R. |author-last=Paul |title=Caldera OpenDOS 7.01/7.02 Update Alpha 3 IBMBIO.COM README.TXT |url=http://www.uni-bonn.de/~uzs180/download/ibmbioa3.zip |date=1997-10-02 |access-date=2009-03-29 |url-status=dead |archive-url=https://web.archive.org/web/20031004074600/http://www-student.informatik.uni-bonn.de/~frinke/ibmbioa3.zip |archive-date=2003-10-04}} [https://web.archive.org/web/20181225154705/http://mirror.macintosharchive.org/max1zzz.co.uk/+Windows%20&%20DOS/DOS/System/Novell/Support/Bins/Op702src.zip<!-- Op702src.zip is an unofficial renamed distribution of the ibmbioa3.zip file -->]</ref>
<ref name="Paul_1997_NWDOSTIP">{{cite book |title=NWDOS-TIPs&nbsp;— Tips & Tricks rund um Novell DOS 7, mit Blick auf undokumentierte Details, Bugs und Workarounds |chapter=II.11.iii. Interne Kommandos und Optionen von COMMAND.COM - Hinweise zu internen Kommandos |series=MPDOSTIP |author-first=Matthias R. |author-last=Paul |date=1997-07-30 |edition=3 |language=de |url=http://www.antonis.de/dos/dos-tuts/mpdostip/html/nwdostip.htm |access-date=2014-08-06 |url-status=live |archive-url=https://web.archive.org/web/20161104235829/http://www.antonis.de/dos/dos-tuts/mpdostip/html/nwdostip.htm |archive-date=2016-11-04}} (NB. NWDOSTIP.TXT is a comprehensive work on [[Novell DOS 7]] and [[OpenDOS 7.01]], including the description of many undocumented features and internals. It is part of the author's yet larger <code>MPDOSTIP.ZIP</code> collection maintained up to 2001 and distributed on many sites at the time. The provided link points to a HTML-converted older version of the <code>NWDOSTIP.TXT</code> file.)</ref>
<ref name="Paul_1997_SETENV">{{cite web |title=SETENV v1.11 |author-first=Matthias R. |author-last=Paul |date=1997-05-27 |orig-year=1996 |url=http://www.uni-bonn.de:80/~uzs180/mpdokeng.html#M.SETENV |url-status=dead |archive-url=https://web.archive.org/web/20090215001349/http://www.uni-bonn.de/~uzs180/mpdokeng.html#M.SETENV |archive-date=15 February 2009 |access-date=29 July 2019 }}</ref>
<ref name="Paul_2002_COM">{{cite web |title=Re: Run a COM file |author-first=Matthias R. |author-last=Paul |date=2002-10-07 |work=alt.msdos.programmer |url=https://groups.google.com/d/msg/alt.msdos.programmer/d7blJjY0H5M/Qu3VeTOIGVcJ |access-date=2017-09-03 |url-status=live |archive-url=https://archive.today/20170903230312/https://groups.google.com/forum/%23!msg/alt.msdos.programmer/d7blJjY0H5M/Qu3VeTOIGVcJ |archive-date=2017-09-03}} [https://groups.google.com/d/msg/alt.lang.asm/PNOd9zfYow0/vXbab16j4XwJ]</ref>
}}

==External links==
* [http://www.concretepage.com/os/window8/how-change-drive-letter-windows-8 Change Drive Letter in Windows 8]
* [http://www.novell.com/coolsolutions/tip/14875.html Tips for USB related drive letter issues] {{Webarchive|url=https://web.archive.org/web/20071018023058/http://www.novell.com/coolsolutions/tip/14875.html |date=2007-10-18  }}

{{DEFAULTSORT:Drive Letter Assignment}}
[[Category:Windows architecture]]
[[Category:DOS technology]]
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