format (command)

In computing, format, a command-line utility included in 86-DOS, MS-DOS, IBM PC DOS and OS/2, Microsoft Windows and ReactOS operating systems, carries out disk formatting.

The command is also available in ISIS-II,[1] TRIPOS[2], AmigaDOS[3], OS-9[4], FlexOS[5], SpartaDOS X,[6] 4690 OS[7], PTS-DOS,[8] and in the DEC RT-11[9] operating system. The FreeDOS version was developed by Brian E. Reifsnyder.[10]

The MS-DOS format command
The MS-DOS format command
Operating systemRT-11, 86-DOS, MS-DOS, PC DOS, OS/2, ISIS-II, TRIPOS, AmigaDOS, OS-9, FlexOS, SpartaDOS X, 4690 OS, FreeDOS, PTS-DOS, Microsoft Windows, ReactOS


The command performs the following actions by default on a floppy disk, hard disk drive, solid state (USB), or other magnetic medium (it will not perform these actions on optical media):

  1. clearing the FAT entries by changing them to 0x00
  2. clearing the FAT root directory by changing any values found to 0x00[nb 1][11][12][13]
  3. checking each cluster to see if it is good or bad and marking it as good or bad in the FAT

Optionally (by adding the /S, for "system" switch), Format can also install a Volume Boot Record. With this option, Format writes bootstrap code to the first sector of the volume (and possibly elsewhere as well). Format always writes a BIOS Parameter Block to the first sector, with or without the /S option.

Another option (/Q) allows for what Microsoft calls "Quick Format". With this option the command will not perform steps 2 and 3 above. Format /Q does not alter data previously written to the media.

Typing "Format" with no parameters in MS-DOS 3.2 or earlier would automatically, without prompting the user, format the current drive; however in MS-DOS 3.3 and later it would simply produce the error: "required parameter missing".

Any storage device must have its medium structured to be useful. This process is referred to as "creating a filesystem" in Unix, Linux, or BSD.[14] Under these systems different commands are used. The commands can create many kinds of file systems, including those used by DOS, Windows, and OS/2.

See also


  1. ^ The directory entries get filled with 0x00 since MS-DOS 1.25 and PC DOS 2.0. If the Format command line option /O is provided, the first byte of each dire entry is set to 0xE5h to create a FAT format useable by PC DOS 1.0-1.1. However, not giving /O will significantly speed up directory searches under MS-DOS 1.25 and PC DOS 2.0 and higher. Older versions of MS-DOS, PC DOS, and 86-DOS only supported the 0xE5 marker.


  1. ^ ISIS II Users Guide
  2. ^
  3. ^
  4. ^ Paul S. Dayan (1992). The OS-9 Guru - 1 : The Facts. Galactic Industrial Limited. ISBN 0-9519228-0-7.
  5. ^
  6. ^ SpartaDOS X 4.48 User Guide
  7. ^
  8. ^ "PTS-DOS 2000 Pro User Manual" (PDF). Buggingen, Germany: Paragon Technology GmbH. 1999. Archived (PDF) from the original on 2018-05-12. Retrieved 2018-05-12.
  9. ^
  10. ^
  11. ^ Paterson, Tim (2013-12-19) [1983]. "Microsoft DOS V1.1 and V2.0: /msdos/v20source/FORMAT.TXT". Computer History Museum, Microsoft. Retrieved 2014-03-25. (NB. While the publishers claim this would be MS-DOS 1.1 and 2.0, it actually is SCP MS-DOS 1.25 and a mixture of Altos MS-DOS 2.11 and TeleVideo PC DOS 2.11.)
  12. ^ Shustek, Len (2014-03-24). "Microsoft MS-DOS early source code". Software Gems: The Computer History Museum Historical Source Code Series. Retrieved 2014-03-29. (NB. While the author claims this would be MS-DOS 1.1 and 2.0, it actually is SCP MS-DOS 1.25 and a mixture of Altos MS-DOS 2.11 and TeleVideo PC DOS 2.11.)
  13. ^ Levin, Roy (2014-03-25). "Microsoft makes source code for MS-DOS and Word for Windows available to public". Official Microsoft Blog. Retrieved 2014-03-29. (NB. While the author claims this would be MS-DOS 1.1 and 2.0, it actually is SCP MS-DOS 1.25 and a mixture of Altos MS-DOS 2.11 and TeleVideo PC DOS 2.11.)
  14. ^ newfs(8): EXAMPLE section – FreeBSD System Manager's Manual

Further reading

  • Cooper, Jim (2001). Special Edition Using MS-DOS 6.22, Third Edition. Que Publishing. ISBN 978-0789725738.
  • Kathy Ivens; Brian Proffit (1993). OS/2 Inside & Out. Osborne McGraw-Hill. ISBN 978-0078818714.
  • Frisch, Æleen (2001). Windows 2000 Commands Pocket Reference. O'Reilly. ISBN 978-0-596-00148-3.

External links

Adobe Flash Media Live Encoder

Flash Media Live Encoder (FMLE) was a free live encoding software product from Adobe Systems. It was available for Microsoft Windows and Mac OS.


AmigaOS is a family of proprietary native operating systems of the Amiga and AmigaOne personal computers. It was developed first by Commodore International and introduced with the launch of the first Amiga, the Amiga 1000, in 1985. Early versions of AmigaOS required the Motorola 68000 series of 16-bit and 32-bit microprocessors. Later versions were developed by Haage & Partner (AmigaOS 3.5 and 3.9) and then Hyperion Entertainment (AmigaOS 4.0-4.1). A PowerPC microprocessor is required for the most recent release, AmigaOS 4.

AmigaOS is a single-user operating system based on a preemptive multitasking kernel, called Exec. It includes an abstraction of the Amiga's hardware, a disk operating system called AmigaDOS, a windowing system API called Intuition and a desktop file manager called Workbench.

The Amiga intellectual property is fragmented between Amiga Inc., Cloanto, and Hyperion Entertainment. The copyrights for works created up to 1993 are owned by Cloanto. In 2001, Amiga Inc. contracted AmigaOS 4 development to Hyperion Entertainment and, in 2009 they granted Hyperion an exclusive, perpetual, worldwide license to AmigaOS 3.1 in order to develop and market AmigaOS 4 and subsequent versions.On December 29, 2015, the AmigaOS 3.1 source code leaked to the web; this was confirmed by the rights holder, Hyperion Entertainment.

Comparison of DOS operating systems

This article details various versions of DOS-compatible operating systems.


DECWAR is a multiplayer computer game first written in 1978 at the University of Texas at Austin for the PDP-10. It was developed from a lesser-known two-player version, WAR, adding multi-terminal support for between one and ten players. WAR and DECWAR are essentially multiplayer versions of the classic Star Trek game, but with added strategic elements. The game was later used, by scrubbing copyright notices and replacing them, as MegaWars on CompuServe and Stellar Warrior on GEnie. Both versions ran for years.

Design of the FAT file system

A FAT file system is a specific type of computer file system architecture and a family of industry-standard file systems utilizing it.

The FAT file system is a legacy file system which is simple and robust. It offers good performance even in very light-weight implementations, but cannot deliver the same performance, reliability and scalability as some modern file systems. It is, however, supported for compatibility reasons by nearly all currently developed operating systems for personal computers and many home computers, mobile devices and embedded systems, and thus is a well suited format for data exchange between computers and devices of almost any type and age from 1981 through the present.

Originally designed in 1977 for use on floppy disks, FAT was soon adapted and used almost universally on hard disks throughout the DOS and Windows 9x eras for two decades. Today, FAT file systems are still commonly found on floppy disks, USB sticks, flash and other solid-state memory cards and modules, and many portable and embedded devices. DCF implements FAT as the standard file system for digital cameras since 1998. FAT is also utilized for the EFI system partition (partition type 0xEF) in the boot stage of EFI-compliant computers.

For floppy disks, FAT has been standardized as ECMA-107 and ISO/IEC 9293:1994 (superseding ISO 9293:1987). These standards cover FAT12 and FAT16 with only short 8.3 filename support; long filenames with VFAT are partially patented. According to Google Patents the "Common name space for long and short filenames"(US5758352A) status was expired in 2019, which may mean that patents expired completely.

Disk formatting

Disk formatting is the process of preparing a data storage device such as a hard disk drive, solid-state drive, floppy disk or USB flash drive for initial use. In some cases, the formatting operation may also create one or more new file systems. The first part of the formatting process that performs basic medium preparation is often referred to as "low-level formatting". Partitioning is the common term for the second part of the process, making the data storage device visible to an operating system. The third part of the process, usually termed "high-level formatting" most often refers to the process of generating a new file system. In some operating systems all or parts of these three processes can be combined or repeated at different levels and the term "format" is understood to mean an operation in which a new disk medium is fully prepared to store files.

As a general rule, formatting a disk leaves most if not all existing data on the disk medium; some or most of which might be recoverable with special tools. Special tools can remove user data by a single overwrite of all files and free space.

Ensoniq ASR-10

The Ensoniq ASR-10 was a sampling keyboard produced by Ensoniq between 1992 and 1998. The ASR-10 was a follow up product to the very popular Ensoniq EPS and Ensoniq EPS-16+ performance samplers, and was also available with a piano style weighted keyboard (ASR-88) and a rackmount version (ASR-10R). At the time, the machine was one of the most powerful samplers available.


For computer file systems, fdisk is a command-line utility that provides disk partitioning functions. It is available in DOS, FlexOS, OS/2, and Microsoft Windows operating systems, and in certain ports of FreeBSD, NetBSD, OpenBSD, DragonFly BSD and macOS for compatibility reasons. In versions of the Windows NT operating system line from Windows 2000 onwards, fdisk is replaced by a more advanced tool called diskpart. Similar utilities exist for Unix-like systems, for example, BSD disklabel.


Floptical refers to a type of floppy disk drive that combines magnetic and optical technologies to store data on media similar to standard ​3 1⁄2-inch floppy disks. The name is a portmanteau of the words "floppy" and "optical". It refers specifically to one brand of drive and disk system, but is also used more generically to refer to any system using similar techniques.

The original Floptical technology was announced in 1988 and introduced late in 1991 by Insite Peripherals, a venture funded company set up by Jim Adkisson, one of the key engineers behind the original ​5 1⁄4-inch floppy disk drive development at Shugart Associates in 1976. The main shareholders were Maxell, Iomega and 3M.


HipHop Virtual Machine (HHVM) is an open-source virtual machine based on just-in-time (JIT) compilation that serves as an execution engine for Hack programming language and used to support PHP execution before release of HHVM version 4. By using the principle of JIT compilation, Hack code is first transformed into intermediate HipHop bytecode (HHBC), which is then dynamically translated into x86-64 machine code, optimized, and natively executed. This contrasts with PHP's usual interpreted execution, in which the Zend Engine transforms PHP source code into opcodes that serve as a form of bytecode, and executes the opcodes directly on the Zend Engine's virtual CPU.HHVM is developed by Facebook, with the project's source code hosted on GitHub; it is licensed under the terms of the PHP License and Zend License.

IBM Personal Computer/AT

The IBM Personal Computer AT, more commonly known as the IBM AT and also sometimes called the PC AT or PC/AT, was IBM's second-generation PC, designed around the 6 MHz Intel 80286 microprocessor and released in 1984 as System Unit 5170. The name AT stood for "Advanced Technology," and was chosen because the AT offered various technologies that were then new in personal computers; one such advancement was that the 80286 processor supported protected mode. IBM later released an 8 MHz version of the AT.

Key Code Qualifier

Key Code Qualifier is an error-code returned by a SCSI device.

When a SCSI target device returns a check condition in response to a command, the initiator usually then issues a SCSI Request Sense command. This process is part of a SCSI protocol called Contingent Allegiance Condition. The target will respond to the Request Sense command with a set of SCSI sense data which includes three fields giving increasing levels of detail about the error:

K - sense key - 4 bits, (byte 2 of Fixed sense data format)

C - additional sense code (ASC) - 8 bits, (byte 12 of Fixed sense data format)

Q - additional sense code qualifier (ASCQ) - 8 bits, (byte 13 of Fixed sense data format)The initiator can take action based on just the K field which indicates if the error is minor or major. However all three fields are usually logically combined into a 20 bit field called Key Code Qualifier or KCQ. The specification for the target device will define the list of possible KCQ values. In practice there are many KCQ values which are common between different SCSI device types and different SCSI device vendors. Common values are listed below, you should consult your hardware specific documentation as well.


MS-DOS ( em-es-DOSS; acronym for Microsoft Disk Operating System) is an operating system for x86-based personal computers mostly developed by Microsoft. Collectively, MS-DOS, its rebranding as IBM PC DOS, and some operating systems attempting to be compatible with MS-DOS, are sometimes referred to as "DOS" (which is also the generic acronym for disk operating system). MS-DOS was the main operating system for IBM PC compatible personal computers during the 1980s and the early 1990s, when it was gradually superseded by operating systems offering a graphical user interface (GUI), in various generations of the graphical Microsoft Windows operating system.

MS-DOS was the result of the language developed in the seventies that was used by IBM for its mainframe operating system. Microsoft acquired the rights to meet IBM specifications. IBM licensed and re-released it on August 12, 1981 as PC DOS 1.0 for use in their PCs. Although MS-DOS and PC DOS were initially developed in parallel by Microsoft and IBM, the two products diverged after twelve years, in 1993, with recognizable differences in compatibility, syntax, and capabilities.

During its lifetime, several competing products were released for the x86 platform, and MS-DOS went through eight versions, until development ceased in 2000. Initially MS-DOS was targeted at Intel 8086 processors running on computer hardware using floppy disks to store and access not only the operating system, but application software and user data as well. Progressive version releases delivered support for other mass storage media in ever greater sizes and formats, along with added feature support for newer processors and rapidly evolving computer architectures. Ultimately it was the key product in Microsoft's growth from a programming language company to a diverse software development firm, providing the company with essential revenue and marketing resources. It was also the underlying basic operating system on which early versions of Windows ran as a GUI. It is a flexible operating system, and consumes negligible installation space.

Nexus file

The NEXUS file format (usually .nex or .nxs) is widely used in bioinformatics. Several popular phylogenetic programs such as PAUP*, MrBayes, Mesquite,, MacClade and SplitsTree use this format.

Printf format string

printf format string refers to a control parameter used by a class of functions in the input/output libraries of C and many other programming languages. The string is written in a simple template language: characters are usually copied literally into the function's output, but format specifiers, which start with a % character, indicate the location and method to translate a piece of data (such as a number) to characters.

"printf" is the name of one of the main C output functions, and stands for "print formatted". printf format strings are complementary to scanf format strings, which provide formatted input (parsing). In both cases these provide simple functionality and fixed format compared to more sophisticated and flexible template engines or parsers, but are sufficient for many purposes.

Many languages other than C copy the printf format string syntax closely or exactly in their own I/O functions.

Mismatches between the format specifiers and type of the data can cause crashes and other vulnerabilities. The format string itself is very often a string literal, which allows static analysis of the function call. However, it can also be the value of a variable, which allows for dynamic formatting but also a security vulnerability known as an uncontrolled format string exploit.


RT-11 ("RT" for real-time) is a discontinued small, single-user real-time operating system for the Digital Equipment Corporation PDP-11 family of 16-bit computers. RT-11 was first implemented in 1970 and was widely used for real-time systems, process control, and data acquisition across the full line of PDP-11 computers.

Real-Time Messaging Protocol

Real-Time Messaging Protocol (RTMP) was initially a proprietary protocol developed by Macromedia for streaming audio, video and data over the Internet, between a Flash player and a server. Macromedia is now owned by Adobe, which has released an incomplete version of the specification of the protocol for public use.

The RTMP protocol has multiple variations:

The "plain" protocol which works on top of and uses TCP port number 1935 by default.

RTMPS, which is RTMP over a TLS/SSL connection.

RTMPE, which is RTMP encrypted using Adobe's own security mechanism. While the details of the implementation are proprietary, the mechanism uses industry standard cryptographic primitives.

RTMPT, which is encapsulated within HTTP requests to traverse firewalls. RTMPT is frequently found utilizing cleartext requests on TCP ports 80 and 443 to bypass most corporate traffic filtering. The encapsulated session may carry plain RTMP, RTMPS, or RTMPE packets within.

RTMFP, which is RTMP over UDP instead of TCP, replacing RTMP Chunk Stream. The Secure Real-Time Media Flow Protocol suite has been developed by Adobe Systems and enables end‐users to connect and communicate directly with each other (P2P).While the primary motivation for RTMP was to be a protocol for playing Flash video, it is also used in some other applications, such as the Adobe LiveCycle Data Services ES.

TRS-80 Model 4

The TRS-80 Model 4 was the last Z80-based home computer family sold by Radio Shack from April 1983 through autumn 1991.

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