A disk compression
software utility
Utility software is software designed to help analyze, configure, optimize or maintain a computer. It is used to support the computer infrastructure - in contrast to application software, which is aimed at directly performing tasks that benefit or ...
increases the amount of information that can be stored on a
hard disk drive of given size. Unlike a
file compression
In information theory, data compression, source coding, or bit-rate reduction is the process of encoding information using fewer bits than the original representation. Any particular compression is either lossy or lossless. Lossless 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.
When information needs to be stored to the hard disk, the utility
compresses the information. When information needs to be read, the utility decompresses the information. A disk compression utility overrides the standard
operating system
An operating system (OS) is system software that manages computer hardware, software resources, and provides common services for computer programs.
Time-sharing operating systems schedule tasks for efficient use of the system and may also i ...
routines. Since all
software application
Software is a set of computer programs and associated documentation and data. This is in contrast to hardware, from which the system is built and which actually performs the work.
At the lowest programming level, executable code consists ...
s access the hard disk using these routines, they continue to work after disk compression has been installed.
Disk compression utilities were popular especially in the early 1990s, when
microcomputer hard disks were still relatively small (20 to 80
megabytes). Hard drives were also rather expensive at the time, costing roughly 10
USD
The United States dollar (symbol: $; code: USD; also abbreviated US$ or U.S. Dollar, to distinguish it from other dollar-denominated currencies; referred to as the dollar, U.S. dollar, American dollar, or colloquially buck) is the official ...
per megabyte. For the users who bought disk compression applications, the software proved to be in the short term a more economic means of acquiring more disk space as opposed to replacing their current drive with a larger one. A good disk compression utility could, on average, double the available space with negligible speed loss. Disk compression fell into disuse by the late 1990s, as advances in hard drive technology and manufacturing led to increased capacities and lower prices.
Common disk compression solutions
Standalone hardware
Some of the initial disk compression solutions were hardware-assisted and utilized add-on compressor/decompressor
coprocessor cards in addition to a software driver. Known solutions include:
* Stacker XT/8 and Stacker AT/16 from
Stac Electronics
* Expanz! and Expanz! Plus from
InfoChip Systems
* DiskDoubler dd2000 from
Datran Corporation
*
MRCI (Microsoft Real-Time Compression Interface) from
Microsoft
Microsoft Corporation is an American multinational technology corporation producing computer software, consumer electronics, personal computers, and related services headquartered at the Microsoft Redmond campus located in Redmond, Washin ...
Standalone software
With increasing PC processor power software-only solutions began to reach or even outperform the performance of hardware-assisted solutions in most scenarios. These compression utilities were sold independently. A user had to specifically choose to install and configure the software.
* Squish
and Squish Plus from
Sundog Software
* Stacker from
Stac Electronics
* XtraDrive from
Integrated Information Technology (IIT)
* SuperStor and SuperStor Pro from
AddStor
* DoubleDisk and DoubleDisk Gold from
Vertisoft Systems
* JAM (JAM.SYS) from JAM Software, Kiev, Ukraine
*
DiskDoubler
DiskDoubler (DD) is a data compression utility for compressing files on the Apple Macintosh platform. Unlike most such programs, which compresses numerous files into a single archive for transmission, DiskDoubler is intended to compress single fi ...
from
Salient Software
* Double Density from
Data Becker
Data Becker GmbH & Co. KG was a German publisher of computer books and a company for software and computer accessories based in Düsseldorf. The company ceased operations in March 2014.
History
It was founded in Düsseldorf on January 7, 1981, ...
Bundled software
The idea of
bundling disk compression into new machines appealed to resellers and users. Resellers liked that they could claim more storage space; users liked that they did not have to configure the software. Bundled utilities included (in chronological order):
*
DR DOS 6.0
DR-DOS (written as DR DOS, without a hyphen, in versions up to and including 6.0) is a disk operating system for IBM PC compatibles. Upon its introduction in 1988, it was the first DOS attempting to be compatible with IBM PC DOS and MS-D ...
(1991), from
Digital Research
Digital Research, Inc. (DR or DRI) was a company created by Gary Kildall to market and develop his CP/M operating system and related 8-bit, 16-bit and 32-bit systems like MP/M, Concurrent DOS, FlexOS, Multiuser DOS, DOS Plus, DR DOS and Gr ...
, included a custom version of
AddStor's ''SuperStor''.
*
PalmDOS 1.0
DR-DOS (written as DR DOS, without a hyphen, in versions up to and including 6.0) is a disk operating system for IBM PC compatibles. Upon its introduction in 1988, it was the first DOS attempting to be compatible with IBM PC DOS and MS-D ...
(1992), from
Novell (after acquiring Digital Research), included a
DPMS-enabled version of ''SuperStor''.
*
MS-DOS 6.0
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 ope ...
(1993), from
Microsoft
Microsoft Corporation is an American multinational technology corporation producing computer software, consumer electronics, personal computers, and related services headquartered at the Microsoft Redmond campus located in Redmond, Washin ...
, included ''
DoubleSpace
DriveSpace (initially known as DoubleSpace) 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 ...
'',
which was based in part on
Vertisoft Systems' ''DoubleDisk''. MS-DOS 6.0 introduced the so-called
DOS preload API
DOS is shorthand for the MS-DOS and IBM PC DOS family of operating systems.
DOS may also refer to:
Computing
* Data over signalling (DoS), multiplexing data onto a signalling channel
* Denial-of-service attack (DoS), an attack on a communicati ...
, an undocumented
challenge–response type interface which allowed the disk compression software (
DBLSPACE.BIN) to be loaded automatically even before
CONFIG.SYS was processed.
*
PC DOS 6.1 (1993), from
IBM, while the original release did not include a disk compressor, a custom version of ''SuperStor/DS'' (after acquiring AddStor) was included in a later release, also introducing the preload API in the PC DOS line.
*
MS-DOS 6.2
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 ope ...
(1993), from
Microsoft
Microsoft Corporation is an American multinational technology corporation producing computer software, consumer electronics, personal computers, and related services headquartered at the Microsoft Redmond campus located in Redmond, Washin ...
, included an improved version of ''DoubleSpace''.
*
Novell DOS 7
DR-DOS (written as DR DOS, without a hyphen, in versions up to and including 6.0) is a disk operating system for IBM PC compatibles. Upon its introduction in 1988, it was the first DOS attempting to be compatible with IBM PC DOS and MS-D ...
(1993), from Novell, included a DPMS-enabled version of ''
Stacker 3.12'' (
STACKER.BIN) from
Stac Electronics, which also supported compressed data exchange with remote
NetWare and
PNW servers also running Stacker in order to avoid unnecessary recompression when copying files.
It also introduced support for the DOS 6 preload API in order to maintain compatibility with Microsoft's DoubleSpace in multi-boot scenarios.
A similar mechanism was used to load the optional single- or multi-user
SECURITY" \n\n\nsecurity.txt is a proposed standard for websites' security information that is meant to allow security researchers to easily report security vulnerabilities. The standard prescribes a text file called \"security.txt\" in the well known locat ...
component.
*
PTS-DOS Extended 6.4 (1994), from
PhysTechSoft
PTS-DOS (aka PTS/DOS) is a disk operating system, a DOS clone, developed in Russia by PhysTechSoft and Paragon Technology Systems.
History and versions
PhysTechSoft was formed in 1991 in Moscow, Russia by graduates and members of MIPT, inf ...
, included a disk compression component named ''Folder'' (
FOLDER.SYS)
*
PC DOS 6.3 (1994), from IBM, included a version of ''SuperStor/DS''.
*
MS-DOS 6.22
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 ope ...
(1994), from Microsoft, included ''
DriveSpace
DriveSpace (initially known as DoubleSpace) 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 th ...
'', which was ''DoubleSpace'' with a different
compression algorithm
In information theory, data compression, source coding, or bit-rate reduction is the process of encoding information using fewer bits than the original representation. Any particular compression is either lossy or lossless. Lossless compressio ...
(
DRVSPACE.BIN), after
MS-DOS 6.21
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 oper ...
had to ship without any disk compression software at all for legal reasons.
*
PC DOS 7.0 (1995), from IBM, included a DPMS-enabled version of ''
Stacker 4.02'' from Stac Electronics.
*
Windows 95
Windows 95 is a consumer-oriented operating system developed by Microsoft as part of its Windows 9x family of operating systems. The first operating system in the 9x family, it is the successor to Windows 3.1x, and was released to manufacturi ...
(1995), from Microsoft, included an updated version of ''
DriveSpace 2''.
*
Windows 95 OSR2 (1996), from Microsoft, included a stripped-down version of ''
DriveSpace 3''.
*
Windows 95 Plus! (1996), from Microsoft, included the full version of ''DriveSpace 3''.
*
OpenDOS 7.01
DR-DOS (written as DR DOS, without a hyphen, in versions up to and including 6.0) is a disk operating system for IBM PC compatibles. Upon its introduction in 1988, it was the first DOS attempting to be compatible with IBM PC DOS and MS-D ...
(1997), from
Caldera
A caldera ( ) is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber in a volcano eruption. When large volumes of magma are erupted over a short time, structural support for the rock above the magma chamber is ...
(after acquiring Novell DOS), included a DPMS-enabled version of ''Stacker 3.12''.
*
DR-DOS 7.02
DR-DOS (written as DR DOS, without a hyphen, in versions up to and including 6.0) is a disk operating system for IBM PC compatibles. Upon its introduction in 1988, it was the first DOS attempting to be compatible with IBM PC DOS and MS-D ...
(1998), from Caldera, included a DPMS-enabled version of ''Stacker 3.12''.
DR-DOS 7.02 also added support for Microsoft's ''DriveSpace''.
*
PC DOS 2000 (1998), from IBM, included a DPMS-enabled version of ''Stacker 4.02''.
*
Windows 98
Windows 98 is a consumer-oriented operating system developed by Microsoft as part of its Windows 9x family of Microsoft Windows operating systems. The second operating system in the 9x line, it is the successor to Windows 95, and was released to ...
(1998), from Microsoft, included the full version of ''DriveSpace 3''.
*
DR-DOS 7.03 (1999), from Caldera, included a DPMS-enabled version of ''Stacker 3.12''.
*
Windows 98 SE
Windows 98 is a consumer-oriented operating system developed by Microsoft as part of its Windows 9x family of Microsoft Windows operating systems. The second operating system in the 9x line, it is the successor to Windows 95, and was released to ...
(1999), from Microsoft, included the full version of ''DriveSpace 3''.
*
PTS-DOS Pro 2000
PTS-DOS (aka PTS/DOS) is a disk operating system, a DOS clone, developed in Russia by PhysTechSoft and Paragon Technology Systems.
History and versions
PhysTechSoft was formed in 1991 in Moscow, Russia by graduates and members of MIPT, info ...
(1999), from
Paragon Technology Software, included a disk compression component named ''DATACOMP''.
Other solutions
* Squeeze, a resident DOS file compressor for
Lotus 1-2-3
Lotus 1-2-3 is a discontinued spreadsheet program from Lotus Software (later part of IBM). It was the first killer application of the IBM PC, was hugely popular in the 1980s, and significantly contributed to the success of IBM PC-compatibles i ...
and
Lotus Symphony files from Turner Hall Publishing
* Squish Plus ROM from
Sundog Software, but distributed exclusively through
Personalized Software (now
Thaddeus Computing), was a special
ROM
Rom, or ROM may refer to:
Biomechanics and medicine
* Risk of mortality, a medical classification to estimate the likelihood of death for a patient
* Rupture of membranes, a term used during pregnancy to describe a rupture of the amniotic sac
* ...
chip containing a custom version of Squish Plus with only 36 KB footprint adapted for the
HP Portable Plus
The Hewlett-Packard HP 110 (aka HP Portable and HP 45710A) is an MS-DOS compatible portable computer released in 1984. It uses a Harris 80C86 running at 5.33 MHz with of RAM. It has an 80 character by 16 line monochrome () l ...
.
*
Double Tools for DoubleSpace from
Addstor was an add-on product, enhancing the functionality of the
DoubleSpace
DriveSpace (initially known as DoubleSpace) 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 ...
bundled with
MS-DOS 6.0
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 ope ...
.
* Multimedia Stacker from
Helix Software was a bundle of Stac's
DPMS-enabled Stacker 4.01 combined with
Helix Cloaking
DOS Protected Mode Services (DPMS) is a set of extended DOS memory management services to allow DPMS-enabled DOS drivers to load and execute in extended memory and protected mode.
Not being a DOS extender by itself, DPMS is a minimal set of ex ...
and utilities, utilizing Cloaking's built-in DPMS server to relocate and run in
protected mode.
* THS filesystem (1994–1996 by Thomas Scheuermann), a compressed file system driver for
Linux
Linux ( or ) is a family of open-source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically packaged as a Linux distribution, w ...
, which could read some
CVFs.
* DMSDOS (1996), a Linux kernel driver,
to support the reading and writing of DoubleSpace, DriveSpace 2 & 3, as well as Stacker 3 & 4 volumes.
While
Windows XP
Windows XP is a major release of Microsoft's Windows NT operating system. It was released to manufacturing on August 24, 2001, and later to retail on October 25, 2001. It is a direct upgrade to its predecessors, Windows 2000 for high-end and ...
, from Microsoft, included both a native support and a
command
Command may refer to:
Computing
* Command (computing), a statement in a computer language
* COMMAND.COM, the default operating system shell and command-line interpreter for DOS
* Command key, a modifier key on Apple Macintosh computer keyboards
* ...
named that compresses files on
NTFS
New Technology File System (NTFS) is a proprietary journaling file system developed by Microsoft. Starting with Windows NT 3.1, it is the default file system of the Windows NT family. It superseded File Allocation Table (FAT) as the preferred fil ...
systems, that is not implemented as a separate "compressed drive" like those above.
Operation
Disk compression usually creates a single large file, which becomes a
virtual hard drive. This is similar to how a single physical hard drive can be
partitioned into multiple virtual drives. The compressed drive is accessed via a
device driver.
Compressing existing drives
All drives would initially be empty. The utility to create a drive would usually offer to "compress a current drive". This meant the utility would:
* Create an empty compressed drive, stored on the existing drive.
* Transfer existing files on the old drive to the new compressed drive.
* Increase the size of the new compressed drive as necessary to accommodate more files and allow empty space when done.
* When all files were transferred, the drive letters would be swapped.
Usually certain
system files would not be transferred. For example, OS
swap file
Swap or SWAP may refer to:
Finance
* Swap (finance), a derivative in which two parties agree to exchange one stream of cash flows against another
* Barter
Science and technology
* Swap (computer programming), exchanging two variables in the ...
s would remain only on the host drive.
Compressing the boot drive
A device driver had to be loaded to access the compressed drive. A compressed drive C: required changes to the
boot process
In computing, booting is the process of starting a computer as initiated via hardware such as a button or by a software command. After it is switched on, a computer's central processing unit (CPU) has no software in its main memory, so so ...
as follows:
* The
System BIOS loads sector 0 of the first physical hard drive (
Master Boot Record).
* The partition sector loads sector 0 of the bootable partition (
Volume Boot Record). In this case, it's the host drive.
* Host drive sector 0 loads (in the case of
DOS
DOS is shorthand for the MS-DOS and IBM PC DOS family of operating systems.
DOS may also refer to:
Computing
* Data over signalling (DoS), multiplexing data onto a signalling channel
* Denial-of-service attack (DoS), an attack on a communicat ...
) the DOS BIOS (
IO.SYS
is an essential part of MS-DOS and Windows 9x. It contains the default MS-DOS device drivers (hardware interfacing routines) and the DOS initialization program.
Boot sequence
In the PC bootup sequence, the first sector of the boot disk is ...
,
IBMBIO.COM etc.) Depending on the version, only the first few sectors of the file or the whole file may be loaded into memory. In the first case, the loaded stub contains another loader loading the remainder of the file from disk. In the case of DR-DOS, the BIOS is packed and will decompress itself through an embedded decompression routine.
* The DOS BIOS then loads the DOS kernel (
MSDOS.SYS
MSDOS.SYS is a system file in MS-DOS and Windows 9x operating systems.
In versions of MS-DOS from 1.1x through 6.22, the file comprises the MS-DOS kernel and is responsible for file access and program management. MSDOS.SYS is loaded by the DOS BI ...
,
IBMDOS.COM etc.)
* If the DOS supports the
preload API, the DOS BIOS attempts to load a preloadable compression driver
(
DBLSPACE.BIN,
DRVSPACE.BIN or
STACKER.BIN) from the root of the host drive and attempts to communicate with it through the DOS preload API.
If the driver responds as expected, the DOS BIOS will keep the driver, if not, it will get discarded.
If kept and configured accordingly, drive letters may get swapped, so that the compressed drive becomes C:.
* The DOS BIOS starts
CONFIG.SYS processing by looking for the file in the root of the boot drive. In the case of DR-DOS,
DCONFIG.SYS
CONFIG.SYS is the primary configuration file for the DOS and OS/2 operating systems. It is a special ASCII text file that contains user-accessible setup or configuration directives evaluated by the operating system's DOS BIOS (typically residing ...
takes precedence over CONFIG.SYS, if present.
* Compression drivers not loaded through the preload API may be loaded through
DEVICE statements.
* Depending on configuration and if this hasn't happened already, drive letters may get swapped, so that the compressed drive becomes C:.
* Processing continues from compressed drive.
Performance impact
On systems with slower hard drives, disk compression could actually increase system performance. This was accomplished two ways:
* Once compressed, there was less data to be stored.
* Disk accesses would often be batched together for efficiency.
If the system had to wait frequently for hard drive access to complete (
I/O bound
In computer science, I/O bound refers to a condition in which the time it takes to complete a computation is determined principally by the period spent waiting for input/output operations to be completed. This is the opposite of a task being CPU bo ...
) converting the hard drive to compressed drives could speed up the system significantly. Compression and decompression of the data increases the CPU utilization. If the system was already
CPU bound
{{Unreferenced, date=April 2007
In computer science, a computer is CPU-bound (or compute-bound) when the time for it to complete a task is determined principally by the speed of the central processor: processor utilization is high, perhaps at 100% ...
, disk compression decreases overall performance.
Drawbacks
Some common drawbacks to using disk compression:
* Not all compression utilities would confirm the absence of errors in the
FAT file system before compressing a disk in place. Some errors, such as
crosslinked files, could result in additional data loss during the transfer process.
* The compressed drive is only visible if the device driver is loaded and the compressed drive is mounted. A
boot disk
A boot disk is a removable digital data storage medium from which a computer can load and run (boot) an operating system or utility program. The computer must have a built-in program which will load and execute a program from a boot disk meeting ...
, for example, might not contain the driver. (This was not normally an issue for solutions that came bundled with the operation systems unless booting foreign operating systems, as system utilities like
SYS were modified to copy the compression drivers to boot disks by default,
and the corresponding operation systems would also fall back to look for them on drives other than the boot disk if they couldn't be found there.)
* Uninstallation was problematic if the expanded size of data on the compressed disk was larger than the normal disk capacity.
* Users did not always realize that the large file on the host drive contained the compressed drive. While it was usually "hidden" by default,
users who did find the large file curious or suspicious were able to delete it. This would normally result in data loss.
See also
*
RAM compression
*
Data compression
In information theory, data compression, source coding, or bit-rate reduction is the process of encoding information using fewer bits than the original representation. Any particular compression is either lossy or lossless. Lossless compressio ...
*
Disk fragmentation
In computing, file system fragmentation, sometimes called file system aging, is the tendency of a file system to lay out the contents of files non-continuously to allow in-place modification of their contents. It is a special case of data fragme ...
*
Executable compression
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 origina ...
*
Self-extracting archive
A self-extracting archive (SFX or SEA) is a computer executable program which contains compressed data in an archive file combined with machine-executable program instructions to extract this information on a compatible operating system and ...
*
cramfs
The compressed ROM/RAM file system (or cramfs) is a free ( GPL'ed) read-only Linux file system designed for simplicity and space-efficiency. It is mainly used in embedded and small-footprint systems.
Unlike a compressed image of a conventional ...
*
e2compr
The ext2 or second extended file system is a file system for the Linux kernel (operating system), kernel. It was initially designed by French software developer Rémy Card as a replacement for the extended file system (ext). Having been design ...
*
SquashFS
Squashfs is a compressed read-only file system for Linux. Squashfs compresses files, inodes and directories, and supports block sizes from 4 KiB up to 1 MiB for greater compression. Several compression algorithms are supported. Squashfs is ...
*
MDFAT
DriveSpace (initially known as DoubleSpace) 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 ...
(DoubleSpace)
*
BitFAT (DoubleSpace)
*
MDBPB (DoubleSpace)
Notes
[In crosslinked files, two files are storing at least part of their data in the same location. At least part of one file (the "bad" file) is always lost in this instance. However, if the "bad" file is copied and then deleted, part of the "good" file is deleted as well. Microsoft SCANDISK was created, in part, to perform a better check of the file system prior to compression than the ]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 ope ...
CHKDSK
In computing, CHKDSK (short for "check disk") is a system tool and command in DOS, Digital Research FlexOS, IBM/Toshiba 4690 OS, IBM OS/2, Microsoft Windows and related operating systems. It verifies the file system integrity of a volume and ...
utility.
[For example, DOS associated up to four ]attributes
Attribute may refer to:
* Attribute (philosophy), an extrinsic property of an object
* Attribute (research), a characteristic of an object
* Grammatical modifier, in natural languages
* Attribute (computing), a specification that defines a prope ...
with files: System, Hidden, Read-Only, and Archive. Files with the System or Hidden attributes are often not displayed by default. Files with the System or Read-Only attribute cannot be deleted with the ERASE
Erase may refer to:
*Data erasure, a method of software-based overwriting that completely destroys all electronic data
*Data remanence, the residual representation of data that has been, in some way, nominally erased or removed
* ''Erase'' (album ...
or DEL
Del, or nabla, is an operator used in mathematics (particularly in vector calculus) as a vector differential operator, usually represented by the nabla symbol ∇. When applied to a function defined on a one-dimensional domain, it denotes ...
DOS command. Most compression utilities would mark the drive file with at least one or more of the System, Hidden, and Read-Only attributes (many would use all three). However, files marked with such attributes can be viewed and deleted by other means. In addition, the user can also remove attributes.
References
External links
*
* ff.
*
* {{cite journal , journal=
Smart Computing , url=http://www.smartcomputing.com/editorial/article.asp?article=articles/archive/l0504/9834/9834.asp&guid= , title=How To... Compress Hard Drives , date=April 1999
Compression
Compression may refer to:
Physical science
*Compression (physics), size reduction due to forces
*Compression member, a structural element such as a column
*Compressibility, susceptibility to compression
* Gas compression
*Compression ratio, of a ...
Compression
Compression may refer to:
Physical science
*Compression (physics), size reduction due to forces
*Compression member, a structural element such as a column
*Compressibility, susceptibility to compression
* Gas compression
*Compression ratio, of a ...
Utility software types
Compression file systems