Format (command)

Format (command)
Company type	Software utility
Industry	Computing / Operating systems
Founded	1981
Headquarters	Various (multiplatform)
Products	Disk formatting tool

In the realm of computing, the format command-line tool is utilized for preparing disks and is a fundamental feature in numerous operating systems, including 86-DOS, MS-DOS, IBM PC DOS, OS/2, Microsoft Windows, and ReactOS.

Overview

Typically, this utility carries out several operations on storage devices such as floppy disks, hard drives, solid-state drives (USB), or other magnetic storage media (excluding optical discs):

Resetting the File Allocation Table (FAT) entries to
Resetting the FAT root directory entries to
Verifying each cluster’s status and marking them as either usable or defective within the FAT

The process of disk formatting organizes storage media by establishing a functional filesystem. While Unix-like platforms employ alternative commands to generate various filesystems—including those compatible with DOS, Windows, and OS/2—the format command remains indispensable within DOS and Windows systems for initializing storage devices.

Implementations

This command exists across a broad spectrum of operating systems such as Intel ISIS-II, iRMX 86, MetaComCo TRIPOS, AmigaDOS, Zilog Z80-RIO, Microware OS-9, DR FlexOS, TSL PC-MOS, SpartaDOS X, Datalight ROM-DOS, IBM/Toshiba 4690 OS, PTS-DOS, SISNE plus, and the DEC RT-11 platform.

Microsoft DOS and Windows

In the case of MS-DOS, the format utility has been included since its initial release. Employing the /S ("system") parameter allows installation of a Volume Boot Record by embedding bootstrap code into the first sector. Regardless of this option’s usage, Format always writes a BIOS Parameter Block at the sector’s start.

The /Q flag activates "Quick Format," which bypasses certain formatting procedures and does not erase existing data. In MS-DOS versions 3.2 or earlier, issuing "format" without any arguments would automatically format the current drive; however, from version 3.3 onward, it produces an error if parameters are omitted.

DR/Novell DOS

The format command in DR DOS 6.0 includes its own version that supports disk preparation alongside system boot setup.

FreeDOS

The FreeDOS variant of format was created by Brian E. Reifsnyder and is distributed under the terms of the GPL, consistent with FreeDOS’s open-source philosophy.

ReactOS

ReactOS’s implementation of format originates from a free clone developed by Mark Russinovich for Sysinternals in 1998 under GPL licensing. Later adapted by Emanuele Aliberti in 1999, it accommodates multiple filesystem types including FAT, FAT32, FATX, as well as Linux filesystems like EXT2 and BtrFS, thereby broadening ReactOS’s support for diverse storage formats.

Notes

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