Editing IBMBIO.COM

{{Short description|System file (DOS BIOS) in PC DOS and DR-DOS}}
{{Use dmy dates|date=April 2019|cs1-dates=y}}
{{Use list-defined references|date=December 2021}}
[[File:IBM PC DOS 1.0 screenshot.png|thumb|300px|<code>IBMBIO.COM</code> (at the top of the listing of [[COM file]]s) in [[IBM PC DOS]] 1.0.]] 
'''IBMBIO.COM''' is a [[system file]] in many [[DOS]] operating systems. It contains the system initialization code and all built-in device drivers. It also loads the DOS kernel ([[IBMDOS.COM]]) and optional pre-loadable system components (like for [[disk compression]] or security),<ref name="Schulman_1994_Undocumented-DOS"/><ref name="Paul_1997_OD-A3"/> displays boot menus, processes configuration files (like [[CONFIG.SYS]]) and launches the shell (like [[COMMAND.COM]]).

The file is part of [[IBM]]'s [[PC&nbsp;DOS]] (all versions) as well as of [[DR&nbsp;DOS 5.0]] and higher (with the exception of [[DR-DOS&nbsp;7.06]]<!-- where it is called IO.SYS -->).<ref name="Paul_1997_OD-A3"/><ref name="Paul_2017"/> It serves the same purpose as the file [[IO.SYS]] in [[MS-DOS]], or DRBIOS.SYS in [[DR&nbsp;DOS&nbsp;3.31]] to [[DR&nbsp;DOS&nbsp;3.41|3.41]].<ref name="Paul_1997_OD-A3"/><ref name="Paul_2017"/> (For compatibility purposes with some DOS applications the IBMBIO.COM file name was briefly also used by the IBM version of [[OS/2 1.0]], where it resembled the [[OS2BIO.COM]] file as used by [[Microsoft]].)

The file is located in the [[root directory]] of the bootable [[File Allocation Table|FAT]]-formatted drive/partition (typically C:\) and typically has the ''system'', ''hidden'', and (since DOS 2.0 also the) ''read-only'' [[file attribute]]s set.<ref name="Duncan_1988_MS-DOS_Encyclopedia"/><ref name="Paul_1997_NWDOSTIP"/><ref name="Paul_2001_NWDOSTIP"/><ref name="Paul_1997_OD-A3"/><ref name="Paul_2017"/> Under DR-DOS the file may be optionally [[FAT file password|password-protected]] as well.<ref name="Paul_2017"/><ref group="nb" name="NB_DR-DOS_Password"/> Under PC&nbsp;DOS, the ''system'' attribute is set in order to mark the file as non-movable, a restriction technically not necessary under DR-DOS.<ref name="Rosch_1991_SYS"/><ref name="Paul_1997_NWDOSTIP"/><ref name="Paul_2001_NWDOSTIP"/><ref name="Paul_2002"/><ref name="Paul_2017"/> As IBMBIO.COM is a binary image containing executable code rather than a true [[COM file|COM]]-style program, the ''hidden'' attribute is set to keep the file from being accidentally invoked at the command prompt, which would lead to a crash.<ref name="Paul_1997_NWDOSTIP"/> This is no longer necessary for [[DR-DOS 7.02]] and higher, because under these systems the file is a [[fat binary]] also containing a tiny COM-style stub just displaying some version info and exiting gracefully when not being loaded by a [[boot sector]].<ref name="Paul_1997_OD-A3"/><ref name="Paul_1997_NWDOSTIP"/><ref name="Caldera_1998_NEW703"/>

In the [[IBM PC compatible|PC]] [[bootup]] sequence, the first sector of the boot volume contains a [[boot loader]] called the [[volume boot record]] (VBR) and is loaded into memory and executed.

If this is a VBR of PC&nbsp;DOS before 3.3 it would load both system files into memory by itself.<ref name="Duncan_1988_MS-DOS_Encyclopedia"/><ref name="Chappell_1994_DOS-Internals"/> As the PC&nbsp;DOS VBR cannot mount the FAT file system, the system files have to be stored in the first directory entries on the disk and be located at fixed physical positions on the disk stored in consecutive sectors, conditions of which the [[SYS (DOS command)|SYS]] utility must take care of.<ref name="Duncan_1988_MS-DOS_Encyclopedia"/><ref name="Chappell_1994_DOS-Internals"/>

If the loaded boot sector is a [[PC&nbsp;DOS 3.3]] (or newer) VBR, the requirements are slightly relaxed. The system files still have to be stored in the first two root directory entries on the disk, but the VBR will use only the first entry to load the first three sectors of IBMBIO.COM into memory and transfer control to it.<ref name="Chappell_1994_DOS-Internals"/><ref group="nb" name="NB_PC_DOS_Contiguous_files"/> This part of IBMBIO.COM then contains a somewhat larger boot loader which:
#Loads the rest of itself into memory. Before [[PC&nbsp;DOS&nbsp;5.0]] the system files still had to be stored at fixed physical positions on the disk and stored in consecutive sectors. With PC&nbsp;DOS&nbsp;5.0 (and higher) this requirement was reduced down to the first three sectors of IBMBIO.COM only.<ref name="Chappell_1994_DOS-Internals"/><ref group="nb" name="NB_PC_DOS_Contiguous_files"/> 
#Loads the DOS kernel. The kernel is stored in [[IBMDOS.COM]].
#Initializes each default [[device driver]] in turn ([[System console|console]], disk, [[serial port]], et cetera). At this point, the default devices are available. 
#Calls the DOS kernel's initialization routine.

Under [[DR&nbsp;DOS 5.0]] and higher, the first step is skipped, since a DR-DOS VBR is capable of mounting the FAT file system, locate the IBMBIO.COM (or DRBIOS.SYS) file anywhere in the root directory and load it into memory by itself.<ref name="Rosch_1991_SYS"/><ref name="Paul_1997_OD-A3"/><ref name="Paul_1997_NWDOSTIP"/><ref name="Paul_2001"/><ref name="Paul_2002"/><ref name="Paul_2017"/><ref group="nb" name="NB_DR-DOS_File-size"/><ref group="nb" name="NB_DR-DOS_707"/> The filename of the IBMBIO.COM file to be loaded by the boot sector is stored in the boot sector rather than necessarily in the first root directory entry, likewise the filename of the IBMDOS.COM file to be loaded by IBMBIO.COM is stored in IBMBIO.COM itself rather than necessarily in the second directory entry on the disk.<ref name="Novell_1993_LOADER"/><ref name="Paul_1997_OD-A3"/><ref name="Paul_1997_NWDOSTIP"/><ref name="Paul_2017"/> Also, similar to the IBMBIO.COM loader in the VBR, the IBMDOS.COM loader in IBMBIO.COM is capable of rudimentarily mounting the filesystem as well, therefore it is not necessary for the system files to be stored in the first two directory entries, to reside at fixed physical positions or be stored in consecutive sectors. Consequently, it is also no longer necessary to set the ''system'' attribute.<ref name="Rosch_1991_SYS"/><ref name="Paul_1997_NWDOSTIP"/><ref name="Paul_2001_NWDOSTIP"/><ref name="Paul_2002"/><ref name="Paul_2017"/> Instead, the system files can be simply copied to the disk (without SYS), given a DR-DOS boot sector already resides on the disk.<ref name="Paul_1997_NWDOSTIP"/><ref name="Paul_2001_NWDOSTIP"/><ref name="Paul_1997_OD-A3"/><ref name="Paul_2002"/><ref name="Paul_2017"/>

Microsoft sometimes calls this component the I/O system,<ref name="Duncan_1988_MS-DOS_Encyclopedia"/><ref name="Paterson_1994_Origins_DOS"/><ref name="Paterson_2007_Design-DOS"/> but it is generally known as DOS BIOS (the DOS-related part of the [[Basic Input/Output System]]). The term BIOS was originally coined by [[Gary Kildall]] in 1975 for [[BIOS (CP/M)|CP/M]],<ref name="Kildall_1975_BIOS"/><ref name="Kildall_1980_CPM"/><ref name="Shustek_2016"/><ref name="Kildall_1993"/><ref name="Fischer_2001_Ewing"/><ref name="Fraley_2007_Killian"/> but is also used to describe a similar component or layer in other operating systems by Digital Research, IBM, Microsoft<!-- f.e. BIOS in MSX-DOS --> and many others.

In a more generic sense, some vendors refer to this portion as the RAM BIOS of operating systems such as [[DOS]] or [[CP/M]] in order to contrast it with the built-in ROM BIOS of a machine.<ref name="ACT_1984_Apricot-Portable"/>

==See also==
<!-- * [[DRBIOS.SYS]] -->
* [[List of DOS system files]]
* [[Hardware abstraction layer]] (HAL)
* [[RPLOADER]]

==Notes==
{{Reflist|group="nb"|refs=
<ref group="nb" name="NB_PC_DOS_Contiguous_files">The [[PC&nbsp;DOS&nbsp;5.0]] manual incorrectly states that the system files no longer need to be contiguous. However, for the boot process to work the system files still need to occupy the first two directory entries and the first three sectors of IBMBIO.COM still need to be stored contiguously.{{citeref|Chappell|1994|b}} [[SYS (DOS command)|SYS]] continues to take care of these requirements.<!-- See Chappell "DOS Internals" for further details --></ref>
<ref group="nb" name="NB_DR-DOS_Password">In addition to the ''read-only'' attribute being set, the system files can be optionally [[FAT file password|password-protected]] under [[DR-DOS]] using the PASSWORD command or the <code>/R[:password]</code> option available in some<!-- at least 7.07 --> versions of the [[SYS (DOS command)|SYS]] command.{{citeref|Paul|2017|a}} The boot loader would simply ignore a set file password while loading the file, but once the system has been booted, the system files could not be accessed without knowing the password, thereby providing an additional level of protection from accidental attempts to delete or modify the system files. (This file password feature is independent of volume or boot passwords also provided by DR-DOS in certain configurations.)</ref>
<ref group="nb" name="NB_DR-DOS_File-size">There is one exception to the rule that [[DR-DOS]] [[Volume boot record|VBR]]s will load the whole IBMBIO.COM file into memory: If the IBMBIO.COM file is larger than 29&nbsp;KB, trying to load the whole file into memory would result in the boot loader to [[#Paul-1997-OD-A3|overwrite]] the [[Call stack|stack]] and [[Relocation (computing)|relocated]] [[Disk Parameter Table]] (DPT/FDPB). Therefore, a [[DR-DOS&nbsp;7.07]] VBR would only load the first 29&nbsp;KB of the file into memory, relying on another loader embedded into the first part of IBMBIO.COM to check for this condition and load the remainder of the file into memory by itself if necessary. This does not cause compatibility problems, as due to internal compression<!-- by Andy T. Wightman and Matthias R. Paul -->{{citeref|ref=Paul-1997-OD-A3|c}}{{citeref|Caldera|1998|d}} the IBMBIO.COM's size never exceeded this limit in previous versions without this loader. Combined with a dual entry structure this also allows the system to be loaded by a [[PC&nbsp;DOS]] VBR, which would load only the first three sectors of the file into memory.</ref>
<ref group="nb" name="NB_DR-DOS_707">The extended functionality of the DR-DOS [[volume boot record]] to mount [[FAT12]] and [[FAT16]] file systems via [[Cylinder-head-sector|CHS]], search for the boot file IBMBIO.COM and load it into memory as a whole, even if not stored at a fixed location and in consecutive sectors,{{citeref|Rosch|1991|e}}{{citeref|ref=Paul-1997-OD-A3|f}}{{citeref|ref=Paul-1997-NWDOSTIP|g}}{{citeref|ref=Paul-2001|h}}{{citeref|ref=Paul-2002|i}}{{citeref|Paul|2017|j}} could still be included utilizing conventional [[code optimization]] techniques in [[assembly language]] up to [[DR-DOS 7.05|7.05]]<!-- really DR-DOS 7.05, as 7.06 used the MS-DOS 7.1 boot sector -->, even while maintaining the minimum requirements of a 32&nbsp;KB memory system with only [[8088]]/[[8086]] processor and continuing to support larger sector sizes<!-- physical sector sizes up to 1 KB and logical sector sizes up to 32 KB --> and the <code>SYS /DR:ext</code> multi-boot feature.{{citeref|ref=Paul-1997-OD-A3|f}} For the further addition of alternative boot units, [[logical block addressing|LBA]], [[FAT32]] and the optional facility to also boot [[PC&nbsp;DOS]]/[[MS-DOS]] in addition to DR-DOS, the [[DR-DOS 7.07|7.07]] sectors had to resort to [[self-modifying code]], [[opcode]]-level programming in [[machine language]], controlled utilization of (documented) [[side effect (computer science)|side effect]]s, multi-level data/code [[instruction overlapping|overlapping]] and algorithmic [[fold (function)|fold]]ing techniques to still squeeze everything into the 423<!-- 512-87-2 (ignoring the 3-byte-jump which can be counted as code) --> bytes available for code in a single physical sector of 512 bytes, as it was a requirement for [[backward compatibility|backward]]- and cross-compatibility with other operating systems in [[multi boot]] and [[chain load]] scenarios.</ref>
}}

==References==
{{Reflist|refs=
<ref name="Duncan_1988_MS-DOS_Encyclopedia">{{Cite book |title=The MS-DOS Encyclopedia: versions 1.0 through 3.2 |author-first1=Ray |author-last1=Duncan |author-first2=Steve |author-last2=Bostwick |author-first3=Keith |author-last3=Burgoyne |author-first4=Robert A. |author-last4=Byers |author-first5=Thom |author-last5=Hogan |author-first6=Jim |author-last6=Kyle |author-first7=Gordon |author-last7=Letwin |author-link7=Gordon Letwin |author-first8=Charles |author-last8=Petzold |author-link8=Charles Petzold |author-first9=Chip |author-last9=Rabinowitz |author-first10=Jim |author-last10=Tomlin |author-first11=Richard |author-last11=Wilton |author-first12=Van |author-last12=Wolverton |author-first13=William |author-last13=Wong |author-first14=JoAnne |author-last14=Woodcock |contribution=Technical advisors |contributor-first1=Mark |contributor-last1=Zbikowski |contributor-link1=Mark Zbikowski |contributor-first2=Paul |contributor-last2=Allen |contributor-link2=Paul Allen |contributor-first3=Steve |contributor-last3=Ballmer |contributor-link3=Steve Ballmer |contributor-first4=Reuben |contributor-last4=Borman |contributor-first5=Rob |contributor-last5=Borman |contributor-first6=John |contributor-last6=Butler |contributor-first7=Chuck |contributor-last7=Carroll |contributor-first8=Mark |contributor-last8=Chamberlain |contributor-first9=David |contributor-last9=Chell |contributor-first10=Mike |contributor-last10=Colee |contributor-first11=Mike |contributor-last11=Courtney |contributor-first12=Mike |contributor-last12=Dryfoos |contributor-first13=Rachel |contributor-last13=Duncan |contributor-first14=Kurt |contributor-last14=Eckhardt |contributor-first15=Eric |contributor-last15=Evans |contributor-first16=Rick |contributor-last16=Farmer |contributor-first17=Bill |contributor-last17=Gates |contributor-link17=Bill Gates |contributor-first18=Michael |contributor-last18=Geary |contributor-first19=Bob |contributor-last19=Griffin |contributor-first20=Doug |contributor-last20=Hogarth |contributor-first21=James W. |contributor-last21=Johnson |contributor-first22=Kaamel |contributor-last22=Kermaani |contributor-first23=Adrian |contributor-last23=King |contributor-first24=Reed |contributor-last24=Koch |contributor-first25=James |contributor-last25=Landowski |contributor-first26=Chris |contributor-last26=Larson |contributor-first27=Thomas |contributor-last27=Lennon |contributor-first28=Dan |contributor-last28=Lipkie |contributor-first29=Marc |contributor-last29=McDonald |contributor-link29=Marc McDonald |contributor-first30=Bruce |contributor-last30=McKinney |contributor-first31=Pascal |contributor-last31=Martin |contributor-first32=Estelle |contributor-last32=Mathers |contributor-first33=Bob |contributor-last33=Matthews <!-- |contributor-link33=Robert Matthews (scientist)??? --> |contributor-first34=David |contributor-last34=Melin |contributor-first35=Charles |contributor-last35=Mergentime |contributor-first36=Randy |contributor-last36=Nevin |contributor-first37=Dan |contributor-last37=Newell |contributor-first38=Tani |contributor-last38=Newell |contributor-first39=David |contributor-last39=Norris |contributor-first40=Mike |contributor-last40=O'Leary |contributor-first41=Bob |contributor-last41=O'Rear |contributor-link41=Bob O'Rear |contributor-first42=Mike |contributor-last42=Olsson |contributor-first43=Larry |contributor-last43=Osterman |contributor-first44=Ridge |contributor-last44=Ostling |contributor-first45=Sunil |contributor-last45=Pai |contributor-first46=Tim |contributor-last46=Paterson |contributor-link46=Tim Paterson |contributor-first47=Gary |contributor-last47=Perez |contributor-first48=Chris |contributor-last48=Peters |contributor-first49=Charles |contributor-last49=Petzold |contributor-link49=Charles Petzold |contributor-first50=John |contributor-last50=Pollock |contributor-first51=Aaron |contributor-last51=Reynolds |contributor-link51=Aaron R. Reynolds |contributor-first52=Darryl |contributor-last52=Rubin |contributor-first53=Ralph |contributor-last53=Ryan |contributor-first54=Karl |contributor-last54=Schulmeisters |contributor-first55=Rajen |contributor-last55=Shah |contributor-first56=Barry |contributor-last56=Shaw |contributor-first57=Anthony |contributor-last57=Short |contributor-first58=Ben |contributor-last58=Slivka |contributor-first59=Jon |contributor-last59=Smirl |contributor-first60=Betty |contributor-last60=Stillmaker |contributor-first61=John |contributor-last61=Stoddard |contributor-first62=Dennis |contributor-last62=Tillman |contributor-first63=Greg |contributor-last63=Whitten |contributor-first64=Natalie |contributor-last64=Yount |contributor-first65=Steve |contributor-last65=Zeck |date=1988 |edition=Completely reworked |publisher=[[Microsoft Press]] |location=Redmond, Washington, USA |isbn=1-55615-049-0 |lccn=87-21452 |oclc=16581341}} (xix+1570 pages; 26&nbsp;cm) (NB. This edition was published in 1988 after extensive rework of the withdrawn 1986 first edition by a different team of authors. [https://www.pcjs.org/pubs/pc/reference/microsoft/mspl13/msdos/encyclopedia/])</ref>
<ref name="Kildall_1975_BIOS">{{cite book |title=CP/M 1.1 or 1.2 BIOS and BDOS for Lawrence Livermore Laboratories |date=June 1975 |author-first=Gary Arlen |author-last=Kildall |author-link=Gary Arlen Kildall |quote=An excerpt of the BDOS.PLM file header in the [[PL/M]] source code of [[CP/M 1.1]] or [[CP/M 1.2]] for [[Lawrence Livermore Laboratories]] (LLL)}}<pre>[…]
/* C P / M   B A S I C   I / O    S Y S T E M    (B I O S)
                    COPYRIGHT (C) GARY A. KILDALL
                             JUNE, 1975                   */
[…]
/*  B A S I C   D I S K    O P E R A T I N G   S Y S T E M  (B D O S)
                    COPYRIGHT (C) GARY A. KILDALL
                            JUNE, 1975                          */
[…]</pre><!-- some whitespace removed from original citation --></ref>
<ref name="Kildall_1980_CPM">{{cite journal |title=The History of CP/M, The Evolution of an Industry: One Person's Viewpoint |author-first=Gary Arlen |author-last=Kildall |author-link=Gary Arlen Kildall |date=January 1980 |journal=[[Dr. Dobb's Journal of Computer Calisthenics & Orthodontia]] |pages=6–7 |volume=5 |issue=1 <!-- |number=41 --> |url=http://www.retrotechnology.com/dri/CPM_history_kildall.txt |access-date=2013-06-03 |url-status=live |archive-url=https://web.archive.org/web/20161124221907/http://www.retrotechnology.com/dri/CPM_history_kildall.txt |archive-date=2016-11-24
|quote=[…] The first commercial licensing of [[CP/M]] took place in 1975 with contracts between [[Digital Systems (Seattle)|Digital Systems]]<!-- a company by [[John Torode (physicist)|John Torode]] --> and [[Omron of America]] for use in their intelligent terminal, and with [[Lawrence Livermore Laboratories]] where CP/M was used to monitor programs in the [[Octopus (network)|Octopus network]]. Little attention was paid to CP/M for about a year. In my spare time, I worked to improve overall facilities […] By this time, CP/M had been adapted for four different controllers. […] In 1976, [[Glenn Ewing]] approached me with a problem: [[IMSAI|Imsai]], Incorporated, for whom Glenn consulted, had shipped a large number of disk subsystems with a promise that an operating system would follow. I was somewhat reluctant to adapt CP/M to yet another controller, and thus the notion of a separated Basic I/O System (BIOS) evolved. In principle, the hardware dependent portions of CP/M were concentrated in the BIOS, thus allowing Glenn, or anyone else, to adapt CP/M to the Imsai equipment. Imsai was subsequently licensed to distribute [[CP/M 1.3|CP/M version 1.3]], which eventually evolved into an operating system called [[IMDOS]]. […]}}</ref>
<ref name="Fischer_2001_Ewing">{{cite web |title=Gary Kildall's CP/M: Some early CP/M history - 1976–1977 |author-first=A. Joseph "Joe" |author-last=Killian |author-link=Joe Killian |publisher=[[Thomas Fischer (IMSAI)|Thomas "Todd" Fischer]], [[IMSAI]] |year=2001 |url=http://www.imsai.net/history/imsai_history/cp-m_history.htm |access-date=2013-06-03 |url-status=live |archive-url=https://web.archive.org/web/20200324173547/https://www.imsai.net/history/imsai_history/cp-m_history.htm |archive-date=2020-03-24 |quote=[…] When [[IMSAI|we]] failed to produce an operating system in a timely manner, [[Glenn Ewing|Glenn]] started talking with Gary about [[CP/M|CPM]] […] It took several months of twisting Gary's arm to get Gary to port it to the 8080. The final success came when Glenn talked Gary into just separating the I/O from the rest of it, with Glenn promising to re-write the I/O module for the [[IMSAI 8080]] (which he did). So CPM on the [[IMSAI]] was a joint effort between Glenn and Gary. […]}}</ref>
<ref name="Fraley_2007_Killian">{{cite web |title=Oral History of Joseph Killian, Interviewed by: Bob Fraley, Edited by: Dag Spicer, Recorded: 2007-01-26 |location=Mountain View, California |id=CHM Reference number: X3879.2007 |author-first1=Bob |author-last1=Fraley |author-first2=Dag |author-last2=Spicer |date=2007-01-26 |publisher=[[Computer History Museum]] |url=http://archive.computerhistory.org/resources/access/text/2012/10/102658016-05-01-acc.pdf |access-date=2013-06-03 |url-status=dead |archive-url=https://web.archive.org/web/20140714175258/http://archive.computerhistory.org/resources/access/text/2012/10/102658016-05-01-acc.pdf |archive-date=2014-07-14 |quote=[[Joe Killian|Killian]]: "[…] [[Glenn Ewing|Glenn]] […] would be talking with [[Gary Kildall|Gary]], and he started twisting Gary's arm. He said, "Hey Gary, why can't we run this in this [[IMSAI]]?" "The I/O's all different, won't run." But Glenn persists and finally makes a deal with Gary. He says, "Okay Gary, if you split out the I/O, I'll write the [[BIOS]], basic I/O's system," and Glenn named it then. "We'll split it out separately. I'll write that part, as long as you can make a division in the program there." And he got Gary to do that and Glenn put those two pieces together and was running Gary's CP/M on an IMSAI. Glenn let us know that, and it wasn't too much later than [[Bill Millard|Bill]] was down there making arrangements with Gary Kildall to license [[CP/M]]. […] Now that the BIOS is separated out, anybody could write a BIOS for their machine, if it was 8080-based, and run this, so he started selling that separately under the company [[Digital Research]] that he formed and did quite well."}}</ref>
<ref name="Shustek_2016">{{cite web |title=In His Own Words: Gary Kildall |author-first=Len |author-last=Shustek |date=2016-08-02 |work=Remarkable People |publisher=[[Computer History Museum]] |url=http://www.computerhistory.org/atchm/in-his-own-words-gary-kildall/ |access-date=2020-02-24 |url-status=live |archive-url=https://web.archive.org/web/20200324173535/https://computerhistory.org/blog/in-his-own-words-gary-kildall/?key=in-his-own-words-gary-kildall |archive-date=2020-03-24}}</ref>
<ref name="Kildall_1993">{{cite book |orig-year=1993 |date=2016-08-02 |title=Computer Connections: People, Places, and Events in the Evolution of the Personal Computer Industry |author-first=Gary Arlen |author-last=Kildall |author-link=Gary Arlen Kildall |editor-first1=Scott |editor-last1=Kildall |editor-link=Scott Kildall |editor-first2=Kristin |editor-last2=Kildall |publisher=Kildall Family |type=Manuscript, part 1 |url=http://www.computerhistory.org/atchm/computer-history-museum-license-agreement-for-the-kildall-manuscript/ |access-date=2016-11-17 |url-status=live |archive-url=https://web.archive.org/web/20161117232745/http://s3data.computerhistory.org/kildall-p.1-78-publishable-lowres.pdf |archive-date=2016-11-17}}</ref>
<ref name="Paul_1997_NWDOSTIP">{{anchor|Paul-1997-NWDOSTIP}}{{cite book |title=NWDOS-TIPs &mdash; Tips & Tricks rund um Novell DOS 7, mit Blick auf undokumentierte Details, Bugs und Workarounds |series=MPDOSTIP |author-first=Matthias R. |author-last=Paul |date=1997-07-30 |orig-year=1994-05-01 |edition=3 |language=de |url=http://www.antonis.de/dos/dos-tuts/mpdostip/html/nwdostip.htm |access-date=2012-01-11 |url-status=live |archive-url=https://web.archive.org/web/20161105172944/http://www.antonis.de/dos/dos-tuts/mpdostip/html/nwdostip.htm |archive-date=2016-11-05}} (NB. <code>NWDOSTIP.TXT</code> 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><!-- still named TIPS_MP.ZIP between 1991 and 1996-11 --> 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 file.) [https://web.archive.org/web/20190601152204/https://www.sac.sk/download/text/mpdostip.zip<!-- A yet older version 155 from 1997-05-13 of the 1997-07-15 distribution archive. -->]</ref>
<ref name="Paul_2001_NWDOSTIP">{{cite book |title=NWDOS-TIPs &mdash; Tips & Tricks rund um Novell DOS 7, mit Blick auf undokumentierte Details, Bugs und Workarounds |series=MPDOSTIP |author-first=Matthias R. |author-last=Paul |date=2001-04-09 |edition=3 |language=de}}</ref>
<ref name="Paul_1997_OD-A3">{{anchor|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 and BOOT.TXT - A short description of how OpenDOS is booted |url=http://www.uni-bonn.de/~uzs180/download/ibmbioa3.zip |date=1997-10-02 |orig-year=1997-09-29 |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_2001">{{anchor|Paul-2001}}{{cite web |title=FAT32 in DR-DOS |author-first=Matthias R. |author-last=Paul |date=2001-01-17 |work=opendos@delorie |url=http://www.delorie.com/opendos/archives/browse.cgi?p=opendos/2001/01/17/02:29:47 |access-date=2017-10-06 |url-status=live |archive-url=https://web.archive.org/web/20171006205537/http://www.delorie.com/opendos/archives/browse.cgi?p=opendos%2F2001%2F01%2F17%2F02%3A29%3A47 |archive-date=2017-10-06 |quote=[…] The DR-DOS boot sector […] searches for the IBMBIO.COM (DRBIOS.SYS) file and then loads the *whole* file into memory before it passes control to it. […]}}</ref>
<ref name="Paul_2002">{{anchor|Paul-2002}}{{cite web |title=Can't copy |author-first=Matthias R. |author-last=Paul |date=2002-02-20 |work=opendos@delorie |url=http://www.delorie.com/opendos//archives/browse.cgi?p=opendos/2002/02/20/16:17:57 |access-date=2017-10-06 |url-status=live |archive-url=https://web.archive.org/web/20171006211007/http://www.delorie.com/opendos//archives/browse.cgi?p=opendos%2F2002%2F02%2F20%2F16%3A17%3A57 |archive-date=2017-10-06 |quote=[…] The [[DR-DOS]] boot sector loads the whole IBMBIO.COM file into memory before it executes it. It does not care at all about the [[IBMDOS.COM]] file, which is loaded by IBMBIO.COM. […] The DR-DOS boot sector […] will find the […] kernel files as long as they are logically stored in the root directory. Their physical location on the disk, and if they are fragmented or not, is don't care for the DR-DOS boot sector. Hence, you can just copy the kernel files to the disk (even with a simple [[COPY (DOS command)|COPY]]), and as soon as the boot sector is a DR-DOS sector, it will find and load them. Of course, it is difficult to put all this into just 512 bytes, the size of a single sector, but this is a major convenience improvement if you have to set up a DR-DOS system, and it is also the key for the DR-DOS multi-OS [[LOADER.COM|LOADER]] utility to work. The [[MS-DOS]] kernel files must reside on specific locations, but the DR-DOS files can be anywhere, so you don't have to physically swap them around each time you boot the other OS. Also, it allows to upgrade a DR-DOS system simply by copying the kernel files over the old ones, no need for [[SYS (DOS command)|SYS]], no difficult setup procedures as required for MS-DOS/PC DOS. You can even have multiple DR-DOS kernel files under different file names stored on the same drive, and LOADER will switch between them according to the file names listed in the [[BOOT.LST]] file. […]}}</ref>
<ref name="Paul_2017">{{cite web |title=The continuing saga of Windows 3.1 in enhanced mode on OmniBook 300 |author-first=Matthias R. |author-last=Paul |orig-year=2017-08-07 |date=2017-08-14 |work=MoHPC - the Museum of HP Calculators |url=http://hpmuseum.org/forum/thread-8774-post-76925.html#pid76925 |access-date=2017-10-06 |url-status=live |archive-url=https://web.archive.org/web/20171006204718/http://hpmuseum.org/forum/thread-8774-post-76925.html |archive-date=2017-10-06 |quote=[…] the DR-DOS [[FDISK (DOS command)|FDISK]] does not only partition a disk, but can also format the freshly created volumes and initialize their boot sectors in one go, so there's no risk to accidentally mess up the wrong volume and no need for [[FORMAT (DOS command)|FORMAT]] /S or [[SYS (DOS command)|SYS]]. Afterwards, you could just copy over the remaining DR-DOS files, including the system files. It is important to know that, in contrast to MS-DOS/PC DOS, DR-DOS has "smart" boot sectors which will actually "mount" the file-system to search for and load the system files in the root directory instead of expecting them to be placed at a certain location. Physically, the system files can be located anywhere and also can be fragmented. […]}}</ref>
<ref name="Schulman_1994_Undocumented-DOS">{{cite book |author-first1=Andrew |author-last1=Schulman |author-first2=Ralf D. |author-last2=Brown |author-link2=Ralf D. Brown |author-first3=David |author-last3=Maxey |author-first4=Raymond J. |author-last4=Michels |author-first5=Jim |author-last5=Kyle |title=Undocumented DOS: A programmer's guide to reserved MS-DOS functions and data structures - expanded to include MS-DOS 6, Novell DOS and Windows 3.1 |publisher=[[Addison Wesley]] |edition=2 |date=1994 |orig-year=November 1993<!-- first printing --> |isbn=0-201-63287-X |location=Reading, Massachusetts |url-access=registration |url=https://archive.org/details/undocumenteddosp00andr_0}} (xviii+856+vi pages, 3.5"-floppy) Errata: [https://web.archive.org/web/20190417215556/http://www.cs.cmu.edu/afs/cs/user/ralf/pub/books/UndocumentedDOS/errata.ud2][https://web.archive.org/web/20190417212906/https://www.pcjs.org/pubs/pc/programming/Undocumented_DOS/#errata-2nd-edition]</ref>
<ref name="Caldera_1998_NEW703">{{cite book |ref={{harvid|Caldera|1998}} |title=DR-DOS 7.03 WHATSNEW.TXT - Changes from DR-DOS 7.02 to DR-DOS 7.03 |publisher=[[Caldera, Inc.]] |date=1998-12-24 |url=http://www.lookas.net/ftp/incoming/darbui/Justas/DRDOS/WHATSNEW.TXT |access-date=2019-04-08 |url-status=dead |archive-url=https://web.archive.org/web/20190408142232/http://www.lookas.net/ftp/incoming/darbui/Justas/DRDOS/WHATSNEW.TXT |archive-date=2019-04-08 |quote=[…] Added a stub which displays the build info if COUNTRY.SYS was erroneously considered being an device driver (DEVICE=COUNTRY.SYS). Also displays the same info if started as .COM program. […] Added a second compression method to further decrease the size of IBMBIO.COM. […]}}</ref>
<ref name="Chappell_1994_DOS-Internals">{{cite book |title=DOS Internals |author-first=Geoff |author-last=Chappell |chapter=Chapter 2: The System Footprint |editor-first1=Andrew |editor-last1=Schulman |editor-first2=Amorette |editor-last2=Pedersen |date=January 1994 |edition=1st printing, 1st |series=The Andrew Schulman Programming Series |publisher=[[Addison Wesley Publishing Company]] |isbn=978-0-201-60835-9 }} (xxvi+738+iv pages, 3.5"-floppy [https://web.archive.org/web/20190421200111/https://gopher.tildeverse.org/gopher.viste.fr/9/programming/PC/DOS/DOS%2520Internals/DOS_Internals.zip][https://web.archive.org/web/20200222111608/https://www.pcjs.org/pubs/pc/programming/DOS_Internals/]) Errata: [https://web.archive.org/web/20200222111742/http://www.geoffchappell.com/notes/dos/internals/][https://web.archive.org/web/20200222111853/https://gopher.tildeverse.org/gopher.viste.fr/1/programming/PC/DOS/DOS%2520Internals/crtdrvr][https://web.archive.org/web/20200222111945/https://gopher.tildeverse.org/gopher.viste.fr/1/programming/PC/DOS/DOS%2520Internals/xmswatch]</ref>
<ref name="Novell_1993_LOADER">{{cite journal |title=Booting Multiple Operating Systems with the DR Multiuser DOS LOADER Utility |volume=5 |number=4 |author-first=Mad |author-last=Poarch<!-- Director, Developer Support/Service --> |journal=Developer Support Bullets |publisher=[[Novell]] |date=April 1993 |url=http://developer.novell.com/support/bullets/apr93.htm#articles |access-date=2013-06-28 |url-status=dead |archive-url=https://web.archive.org/web/20120322220335/http://developer.novell.com/support/bullets/apr93.htm |archive-date=2012-03-22}}</ref>
<ref name="Rosch_1991_SYS">{{cite magazine |title=DR DOS 5.0 - The better operating system? |author-first=Winn L. |author-last=Rosch |magazine=[[PC Magazine]] |date=1991-02-12 |volume=10 |number=3 |pages=<!-- 245, -->241–246, 257, 264, 266 |url=https://books.google.com/books?id=YxFTezF9-sMC&pg=PT250 |access-date=2019-07-26 |url-status=live |archive-url=https://archive.today/20190725223320/https://books.google.nl/books?id=YxFTezF9-sMC&pg=PT250&lpg=PT250&redir_esc=y%23v=onepage&q&f=false |archive-date=2019-07-25 |quote=[…] [[SYS (DOS command)|SYS]] has been improved under [[DR&nbsp;DOS 5.0]] so you don't have to worry about leaving the first cluster free on a disk that you want to make bootable. The DR&nbsp;DOS system files can be located anywhere on the disk, so any disk with enough free space can be set to boot your system. […]}} (NB. The source attributes this to the [[SYS (DOS command)|SYS]] utility while in fact this is a feature of the advanced bootstrap loader in the boot sector. SYS just plants this sector onto the disk.)</ref>
<ref name="ACT_1984_Apricot-Portable">{{cite book |title=Apricot Portable - Technical Reference Manual |volume=Section 3: Software |publisher=[[ACT (International) Limited]] |date=1984 |url=https://archive.org/details/hack42_Apricot_Portable_Technical_Reference_Manual_Sections |access-date=2020-01-13}} (228 pages)</ref>
<ref name="Paterson_1994_Origins_DOS">{{cite journal |title=The Origins of DOS: DOS Creator Gives His View of Relationship Between CP/M, MS-DOS |author-last=Paterson |author-first=Tim |author-link=Tim Paterson |journal=[[Microprocessor Report]] |publisher=[[MicroDesign Resources]] (MDR) |volume=8 |issue=13 |date=1994-10-03 |issn=0899-9341 |url=http://www.ece.umd.edu/courses/enee759m.S2000/papers/paterson1994-kildall.pdf |archive-url=https://web.archive.org/web/20120531090452/http://www.ece.umd.edu/courses/enee759m.S2000/papers/paterson1994-kildall.pdf |archive-date=2012-05-31}}</ref>
<ref name="Paterson_2007_Design-DOS">{{cite web |title=Design of DOS |author-first=Tim |author-last=Paterson |author-link=Tim Paterson |work=DosMan Drivel |date=2007-09-30 |url=http://dosmandrivel.blogspot.com/2007/09/design-of-dos.html |access-date=2011-07-04 |archive-url=https://web.archive.org/web/20130120075653/http://dosmandrivel.blogspot.com/2007/09/design-of-dos.html |archive-date=2013-01-20}}</ref>
}}

{{Disk operating systems}}

[[Category:DOS files]]