File Allocation Table (FAT) is a file system developed for personal computers and was the default filesystem for MS-DOS and Windows 9x operating systems. Originally developed in 1977 for use on floppy disks, it was adapted for use on hard disks and other devices. The increase in disk drives capacity required four major variants: FAT12, FAT16, FAT32, and ExFAT. FAT was replaced with NTFS as the default file system on Microsoft operating systems starting with Windows XP. Nevertheless, FAT continues to be used on flash and other solid-state memory cards and modules, many portable and embedded devices because of its compatibility and ease of implementation.
Disk partitioning or disk slicing is the creation of one or more regions on secondary storage, so that each region can be managed separately. These regions are called partitions. It is typically the first step of preparing a newly installed disk after a partitioning scheme is chosen for the new disk before any file system is created. The disk stores the information about the partitions' locations and sizes in an area known as the partition table that the operating system reads before any other part of the disk. Each partition then appears to the operating system as a distinct "logical" disk that uses part of the actual disk. System administrators use a program called a partition editor to create, resize, delete, and manipulate the partitions. Partitioning allows the use of different filesystems to be installed for different kinds of files. Separating user data from system data can prevent the system partition from becoming full and rendering the system unusable. Partitioning can also make backing up easier. A disadvantage is that it can be difficult to properly size partitions, resulting in having one partition with too much free space and another nearly totally allocated.
ZIP is an archive file format that supports lossless data compression. A ZIP file may contain one or more files or directories that may have been compressed. The ZIP file format permits a number of compression algorithms, though DEFLATE is the most common. This format was originally created in 1989 and was first implemented in PKWARE, Inc.'s PKZIP utility, as a replacement for the previous ARC compression format by Thom Henderson. The ZIP format was then quickly supported by many software utilities other than PKZIP. Microsoft has included built-in ZIP support in versions of Microsoft Windows since 1998 via the "Plus! 98" addon for Windows 98. Native support was added as of the year 2000 in Windows ME. Apple has included built-in ZIP support in Mac OS X 10.3 and later. Most free operating systems have built in support for ZIP in similar manners to Windows and macOS.
The A20, or address line 20, is one of the electrical lines that make up the system bus of an x86-based computer system. The A20 line in particular is used to transmit the 21st bit on the address bus.
RAR is a proprietary archive file format that supports data compression, error correction and file spanning. It was developed in 1993 by Russian software engineer Eugene Roshal and the software is licensed by win.rar GmbH. The name RAR stands for Roshal Archive.
7-Zip is a free and open-source file archiver, a utility used to place groups of files within compressed containers known as "archives". It is developed by Igor Pavlov and was first released in 1999. 7-Zip has its own archive format called 7z, but can read and write several others.
fdisk is a command-line utility for disk partitioning. It has been part of DOS, DR FlexOS, IBM OS/2, and early versions of Microsoft Windows, as well as certain ports of FreeBSD, NetBSD, OpenBSD, DragonFly BSD and macOS for compatibility reasons. Windows 2000 and its successors have replaced fdisk with a more advanced tool called diskpart.
StuffIt Expander is a proprietary, freeware, closed source, decompression software utility developed by Allume Systems. It runs on the classic Mac OS, macOS, and Microsoft Windows. Prior to 2011, a Linux version had also been available for download.
LZX is an LZ77 family compression algorithm, a slightly improved version of DEFLATE. It is also the name of a file archiver with the same name. Both were invented by Jonathan Forbes and Tomi Poutanen in the 1990s.
WinRAR is a trialware file archiver utility, developed by Eugene Roshal of win.rar GmbH. It can create and view archives in RAR or ZIP file formats, and unpack numerous archive file formats. To enable the user to test the integrity of archives, WinRAR embeds CRC32 or BLAKE2 checksums for each file in each archive. WinRAR supports creating encrypted, multi-part and self-extracting archives.
LHA or LZH is a freeware compression utility and associated file format. It was created in 1988 by Haruyasu Yoshizaki, a doctor, and originally named LHarc. A complete rewrite of LHarc, tentatively named LHx, was eventually released as LH. It was then renamed to LHA to avoid conflicting with the then-new MS-DOS 5.0 LH command. The original LHA and its Windows port, LHA32, are no longer in development because Yoshizaki is busy at work.
Stac Electronics, originally incorporated as State of the Art Consulting and later shortened to Stac, Inc., was a technology company founded in 1983. It is known primarily for its Lempel–Ziv–Stac lossless compression algorithm and Stacker disk compression utility for compressing data for storage.
Norton Utilities is a utility software suite designed to help analyze, configure, optimize and maintain a computer. The latest version of the original series of Norton Utilities is Norton Utilities 16 for Windows XP/Vista/7/8, released 26 October 2012.
The following tables compare general and technical information for a number of file archivers. Please see the individual products' articles for further information. They are neither all-inclusive nor are some entries necessarily up to date. Unless otherwise specified in the footnotes section, comparisons are based on the stable versions—without add-ons, extensions or external programs.
Executable compression is any means of compressing an executable file and combining the compressed data with decompression code into a single executable. When this compressed executable is executed, the decompression code recreates the original code from the compressed code before executing it. In most cases this happens transparently so the compressed executable can be used in exactly the same way as the original. Executable compressors are often referred to as executable packers, runtime packers, software packers, software protectors, or even "polymorphic packers" and "obfuscating tools".
PC Tools is a collection of software utilities for DOS developed by Central Point Software.
A disk compression software utility increases the amount of information that can be stored on a hard disk drive of given size. Unlike a file compression utility, which compresses only specified files—and which requires the user to designate the files to be compressed—an on-the-fly disk compression utility works automatically through resident software without the user needing to be aware of its existence. On-the-fly disk compression is therefore also known as transparent, real-time or online disk compression.
DriveSpace is a disk compression utility supplied with MS-DOS starting from version 6.0 in 1993 and ending in 2000 with the release of Windows Me. The purpose of DriveSpace is to increase the amount of data the user could store on disks by transparently compressing and decompressing data on-the-fly. It is primarily intended for use with hard drives, but use for floppy disks is also supported. This feature was removed in Windows XP and later.
A self-extracting archive is a computer executable program which combines compressed data in an archive file with machine-executable code to extract the information. Running on a compatible operating system, it does not need a suitable extractor in the target computer to extract the data. The executable part of the file is known as a decompressor stub.
The Unarchiver is a proprietary freeware data decompression utility, which supports more formats than Archive Utility, the built-in archive unpacker program in macOS. It can also handle filenames in various character encodings, created using operating system versions that use those character encodings. The latest version requires Mac OS X Lion or higher. The Unarchiver does not compress files.
