.sys is a

filename extension A filename extension, file name extension or file extension is a suffix to the name of a computer file (for example, .txt, .mp3, .exe) that indicates a characteristic of the file contents or its intended use. A filename extension is typically d ...

used in MS-DOS applications and

Microsoft Microsoft Corporation is an American multinational corporation and technology company, technology conglomerate headquartered in Redmond, Washington. Founded in 1975, the company became influential in the History of personal computers#The ear ...

Windows Windows is a Product lining, product line of Proprietary software, proprietary graphical user interface, graphical operating systems developed and marketed by Microsoft. It is grouped into families and subfamilies that cater to particular sec ...

operating system An operating system (OS) is system software that manages computer hardware and software resources, and provides common daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), schedule tasks for ...

s. They are system files that contain

device driver In the context of an operating system, a device driver is a computer program that operates or controls a particular type of device that is attached to a computer or automaton. A driver provides a software interface to hardware devices, enabli ...

s or hardware configurations for the system. Most DOS files are

real mode Real mode, also called real address mode, is an operating mode of all x86-compatible CPUs. The mode gets its name from the fact that addresses in real mode always correspond to real locations in memory. Real mode is characterized by a 20- bit s ...

s. Certain files using this extension are not, however: * MSDOS.SYS and IO.SYS are core operating system files in

MS-DOS MS-DOS ( ; acronym for Microsoft Disk Operating System, also known as Microsoft DOS) is an operating system for x86-based personal computers mostly developed by Microsoft. Collectively, MS-DOS, its rebranding as IBM PC DOS, and a few op ...

and

Windows 9x Windows 9x is a generic term referring to a line of discontinued Microsoft Windows operating systems released from 1995 to 2000 and supported until 2006, which were based on the kernel introduced in Windows 95 and modified in succeeding version ...

. * CONFIG.SYS is a

text file A text file (sometimes spelled textfile; an old alternative name is flat file) is a kind of computer file that is structured as a sequence of lines of electronic text. A text file exists stored as data within a computer file system. In ope ...

that contains various configuration options and specifies what device drivers will be loaded. * COUNTRY.SYS is a binary database containing country and codepage related information for use with the CONFIG.SYS COUNTRY directive and the NLSFUNC driver. *

KEYBOARD.SYS This article lists notable commands provided by the MS-DOS disk operating system (DOS), especially as used on an IBM PC compatible computer. Other DOS variants as well as the legacy Windows shell, Command Prompt (cmd.exe), provide many of these c ...

is a binary database containing keyboard layout related information including short

P-code Bytecode (also called portable code or p-code) is a form of instruction set designed for efficient execution by a software interpreter. Unlike human-readable source code, bytecodes are compact numeric codes, constants, and references (normal ...

sequences to be executed by an interpreter inside the KEYB keyboard driver. System files are most commonly found within the Windows directory of a Windows installation. In particular, many SYS files are stored in the Windows\winsxs directory in later versions of Windows.

File location

Windows Vista Windows Vista is a major release of the Windows NT operating system developed by Microsoft. It was the direct successor to Windows XP, released five years earlier, which was then the longest time span between successive releases of Microsoft W ...

and its successors, the .sys files are mainly found under the following paths: : C:\Windows\system32\drivers : C:\Windows\WinSxS In

, the file named MSDOS.SYS is used to copy the system files from one drive to another, allowing the second drive to be bootable. MSDOS.SYS is located in the root directory of the bootable drive/partition (normally C:\ for hard disks) and has the hidden, read-only, and system file attributes set.

References

{{reflist, refs= {{cite web , url=http://www.osronline.com/article.cfm?article=233 , title=Exactly What Is A Driver? , archive-url=https://web.archive.org/web/20070928152834/http://www.osronline.com/article.cfm?article=233 , archive-date=2007-09-28 , date=2003-05-14 , work=OSR {{cite web , url=http://support.microsoft.com/kb/118579 , title=Contents of the Windows Msdos.sys File , date=2004-09-27 , work=Support , publisher=

, url-status=dead , archive-url=https://web.archive.org/web/20041020201313/http://support.microsoft.com/kb/118579 , archive-date=2004-10-20 {{Cite web, url=http://www.dewassoc.com/support/msdos/config_sys.htm, title=What is an Config.sys file?, website=www.dewassoc.com, access-date=2007-02-16 , archive-date=2011-06-29 , archive-url=https://web.archive.org/web/20110629183042/http://www.dewassoc.com/support/msdos/config_sys.htm, url-status=dead {{cite web , title=DOS COUNTRY.SYS file format , type=COUNTRY.LST file , author-first=Matthias R. , author-last=Paul , date=2001-06-10 , edition=1.44 , orig-year=1995 , url=http://www.columbia.edu/~em36/wpdos/MatthiasPaulCPI.zip , access-date=2016-08-20 , url-status=live, archive-url=https://web.archive.org/web/20160420065252/http://www.columbia.edu/~em36/wpdos/MatthiasPaulCPI.zip , archive-date=2016-04-20 {{cite web , title=KEYBOARD.SYS internal structure , publisher=comp.os.msdos.programmer , author-first=Matthias R. , author-last=Paul , date=2001-12-30 , url=https://groups.google.com/d/msg/comp.os.msdos.programmer/l_IuSHsBDWQ/887rJF9IYmMJ , access-date=2016-09-17 , url-status=live , archive-url=https://archive.today/20170909082257/https://groups.google.com/forum/%23!msg/comp.os.msdos.programmer/l_IuSHsBDWQ/887rJF9IYmMJ , archive-date=2017-09-09 , quote= ..In fact, the format is basically the same in MS-DOS 3.3 - 8.0, PC DOS 3.3 - 2000, including Russian, Lithuanian, Chinese and Japanese issues, as well as in Windows NT, 2000, and XP .. There are minor differences and incompatibilities, but the general format has not changed over the years. ..Some of the data entries contain normal tables .. However, most entries contain "executable code" interpreted by some kind of P-code interpreter at *runtime*, including conditional branches and the like. This is why the KEYB driver has such a huge memory footprint compared to table-driven keyboard drivers which can be done in 3 - 4 Kb getting the same level of functionality except for the interpreter. .. {{cite web , title=How to Display the Euro in MS-DOS and Windows DOS , at=Display the euro symbol in full-screen MS-DOS (including Windows 95 or Windows 98 full-screen DOS) , author-first=Edward , author-last=Mendelson , author-link=Edward Mendelson , date=2001-07-20 , url=http://www.columbia.edu/~em36/wpdos/eurodos.html , access-date=2016-09-17 , url-status=live , archive-url=https://web.archive.org/web/20160917201248/http://www.columbia.edu/~em36/wpdos/eurodos.html , archive-date=2016-09-17 , quote= ..Matthias .Paul ..warns that the

IBM PC DOS IBM PC DOS (an acronym for IBM Personal Computer Disk Operating System),Formally known as "The IBM Personal Computer DOS" from versions 1.0 through 3.30, as reported in those versions' respective COMMAND.COM outputs also known as PC DOS or IBM ...

version of the keyboard driver uses some internal procedures that are not recognized by the

driver, so, if possible, you should use the

IBM International Business Machines Corporation (using the trademark IBM), nicknamed Big Blue, is an American Multinational corporation, multinational technology company headquartered in Armonk, New York, and present in over 175 countries. It is ...

versions of both KEYB.COM and

instead of mixing Microsoft and IBM versions ..} (NB. What is meant by "procedures" here are some additional

byte code Bytecode (also called portable code or p-code) is a form of instruction set designed for efficient execution by a software interpreter. Unlike human-readable source code, bytecodes are compact numeric codes, constants, and references (normally ...

s in the IBM KEYBOARD.SYS file not supported by the Microsoft version of the KEYB driver.) {{Cite web, url=https://fileinfo.com/extension/sys, title=SYS File Extension - What is an .sys file and how do I open it?, website=fileinfo.com sys Executable file formats

File location

See also

References