DriveSpace (initially known as DoubleSpace) is a disk compression utility supplied with MS-DOS starting from version 6.0 in 1993. 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.
In the most common usage scenario, the user would have one hard drive in the computer, with all the space allocated to one partition (usually as drive C:). The software would compress the entire drive contents into one large file in the root partition. On booting the system, the driver would allocate this large file as drive C:, enabling files to be accessed as normal.
Instead of developing its own product from scratch, Microsoft licensed the technology for the DoubleDisk product developed by Vertisoft and adapted it to become DoubleSpace. For instance, the loading of the driver controlling the compression/decompression (DBLSPACE.BIN) became more deeply integrated into the operating system (being loaded through the undocumented pre-load API even before the CONFIG.SYS file).
Microsoft had originally sought to license the technology from Stac Electronics, which had a similar product called Stacker, but these negotiations had failed. Microsoft was later successfully sued for patent infringement by Stac Electronics for violating some of its compression patents. During the court case Stac Electronics claimed that Microsoft had refused to pay any money when it attempted to license Stacker, offering only the possibility for Stac Electronics to develop enhancement products.
A few computer programs, particularly games, were incompatible with DoubleSpace because they effectively bypassed the DoubleSpace driver. DoubleSpace also consumed a significant amount of conventional memory, making it difficult to run memory-intensive programs.
Shortly after its release, reports of data loss emerged. A company called Blossom Software claimed to have found a bug that could lead to data corruption. The bug occurred when writing files to heavily fragmented disks and was demonstrated by a program called BUST.EXE. The company sold a program called DoubleCheck that could be used to check for the fragmentation condition that could lead to the error. Microsoft's position was that the error only occurred under unlikely conditions, but fixed the problem in MS-DOS 6.2.
The fragmentation condition was related to the way DoubleSpace compresses individual clusters (of size, say, 8K), and fits them on the disk, occupying fewer sectors (size 512 bytes) than the fixed number required without DoubleSpace (16 sectors in this example). This created the possibility of a kind of internal fragmentation issue, where DoubleSpace would be unable to find enough consecutive sectors for storing a compressed cluster even if plenty of space was available.
Other potential causes of data loss included the corruption of DoubleSpace's memory areas by other programs, DoubleSpace's memory areas were not protected, because MS-DOS ran in real mode. Microsoft attempted to remedy this in the MS-DOS 6.2 version of DoubleSpace (via a feature called DoubleGuard that would check for such corruption).
The fact that the compressed contents of a compressed drive was stored in a single file implied the possibility of a user accidentally deleting all his/her data by deleting just that file. This could happen if the user inadvertently got access to the host drive, containing this file. The host drive was usually mapped to the letter H: by the compression driver. However, if the compression driver had failed to load the user might see it as drive C:
Turning off the computer before DoubleSpace could finish updating its data structures could also result in data loss. This problem was compounded by Microsoft making write caching enabled by default in the SMARTDRV disk cache software that came with MS-DOS 6.0. Because of this change, after exiting an application, the MS-DOS prompt might appear before all data had been written to the disk. However, due to the lack of a controlled shutdown procedure (as found in modern operating systems), many users saw the appearance of the MS-DOS prompt as an indication that it was safe to switch off the computer, which was typically the case prior to MS-DOS 6.0. Microsoft addressed this issue in MS-DOS 6.2 where the write caching was still enabled by default, but where the cache would be flushed before allowing the command prompt to reappear.
AddStor, Inc. offered an add-on product called Double Tools for DoubleSpace. It contained a number of tools to enhance the functions of the version of DoubleSpace that came with MS-DOS 6.0. This included various diagnostic features, the ability to have compressed removable media auto-mounted as they were used, as well as support for background defragmentation of DoubleSpace compressed drives. To defragment files in the background, it was possible to let DoubleTools replace the low-level DoubleSpace driver (DBLSPACE.BIN) with one supplied by DoubleTools. Replacing the driver also enabled other enhanced functionality of the product, such as the use of 32-bit code paths when it detected an Intel 80386 or higher CPU, caching capabilities and - in addition to its supporting the use of the Upper Memory Area - also permitted the use of Extended Memory for some of its buffers (reducing the driver's total footprint in conventional and upper memory, albeit at the cost of somewhat reduced speed). Another function was the ability to split a compressed volume over multiple floppy disks, being able to see the entire volume with only the first disk inserted (and being prompted to change discs as necessary). It was also possible to share a compressed volume with a remote computer. Double Tools also had the capability to put a special utility on compressed floppy disks that made it possible to access the compressed data even on computers that didn't have DoubleSpace (or Double Tools).
Vertisoft, the company who developed the DoubleDisk program that Microsoft subsequently licensed and turned into DoubleSpace, developed and sold a DoubleSpace add-on program called SpaceManager, which contained a number of usability enhancements. It also offered improved compression ratios.
Other products, like later versions of Stacker from Stac Electronics, were capable of converting existing DoubleSpace compressed drives into their own format.
MS-DOS 6.2 featured a new and improved version of DoubleSpace. The ability to remove DoubleSpace was added. The program SCANDISK introduced in this release was able to scan the non-compressed and compressed drives, including checks of the internal DoubleSpace structures. Security features (known as DoubleGuard) were added to prevent memory corruption from leading to data loss. The memory footprint of the DoubleSpace driver was reduced compared to the version shipped in MS-DOS 6.0. A fix was made to the fragmentation issue discussed above.
Following a successful lawsuit by Stac Electronics regarding demonstrated patent infringement, Microsoft released MS-DOS 6.21 without DoubleSpace. A court injunction also prevented any further distribution of the previous versions of MS-DOS that included DoubleSpace.
MS-DOS 6.22 contained a reimplemented version of the disk compression software, but this time released under the name DriveSpace. The software was essentially identical to the MS-DOS 6.2 version of DoubleSpace from a user point of view, and was compatible with previous versions.
Windows 95 had full support of DoubleSpace/DriveSpace via a native 32-bit driver for accessing the compressed drives, along with a graphical version of the software tools. MS-DOS DriveSpace users could upgrade to Windows 95 without any troubles. Furthermore, the Microsoft Plus! for Windows 95 pack contained version 3 of DriveSpace. This version introduced new compression formats (HiPack and UltraPack) with different performance characteristics for even greater compression ratios along with a tool that could recompress the files on the disk using the different formats, depending on how frequently the files were used. One could upgrade from DriveSpace 2 to DriveSpace 3, but there was no downgrade path back to DriveSpace 2. One could, however, decompress a DriveSpace 3 drive. The DOS device driver of DriveSpace 3 had a memory footprint of around 150 KB because of all these new features. This caused difficulty for users rebooting into the MS-DOS mode of Windows 95 for running games, because of the reduced amount of conventional memory that was available.
DriveSpace 3 also shipped with Windows 95 OSR2 but many features were disabled unless Plus! was also installed. DriveSpace could also not be used with FAT32, making it of little use on PCs with large hard drives.
Windows 98 shipped with DriveSpace 3 as part of the operating system. Functionality was the same as in Windows 95 with Plus!.
Because of the removal of real mode support, FAT32 going mainstream and the decreasing popularity of DriveSpace, DriveSpace in Windows ME had only limited support. DriveSpace no longer supported hard disk compression, but still supported reading and writing compressed removable media, although the only DriveSpace operation supported beside that was deleting and reallocating compressed drives.
It is possible to restore full function of DriveSpace 3 (unofficially) in Windows ME, copying the executable file from a Windows 98 installation and using it to replace the executable included with Windows ME. After that, one could compress new drives as they could do on Windows 98.
DMSDOS, a Linux kernel driver, was developed in the late 1990s to support both the reading and writing of DoubleSpace/DriveSpace disks. However, reading and especially writing to compressed filesystems is reliable only in specific versions of the 2.0, 2.1 or 2.2 versions of the kernel.
While DR-DOS supported its own disk compression technology (originally based on SuperStor, later on Stacker), Novell DOS 7 in 1993 and higher introduced an emulation of the undocumented pre-load API in order to provide seamless support for DoubleSpace as well. Since the DR-DOS drivers were DPMS-enabled whereas the MS-DOS one's where not, this did not offer any advantages for DR-DOS users, but allowed easier coexistance or migration due to the possibility of shared use of already existing compressed volumes in multi-boot scenarios. DR-DOS 7.02 and higher also added support for DriveSpace in 1998.
CVF may refer to:
Climate Vulnerable Forum
Carrier Vessel Future, the project name for the Queen Elizabeth class aircraft carrier
Courchevel Airport's IATA code, France
Cyprus Volleyball Federation
Competing values framework
Computer Vision Foundation
Compressed Volume File, container file for compressed FAT volumes by Microsoft DoubleSpace/DriveSpaceComparison of DOS operating systems
This article details various versions of DOS-compatible operating systems.Comparison of file systems
The following tables compare general and technical information for a number of file systems.Disk compression
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 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 routines. Since all software applications 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 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.Disk partitioning
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, 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 much free space and another nearly totally allocated.Disk utility
A disk utility is a utility program that allows a user to perform various functions on a computer disk, such as disk partitioning and logical volume management, as well as multiple smaller tasks such as changing drive letters and other mount points, renaming volumes, disk checking, and disk formatting, which are otherwise handled separately by multiple other built-in commands. Each operating system (OS) has its own basic disk utility, and there are also separate programs which can recognize and adjust the different filesystems of multiple OSes. Types of disk utilities include disk checkers, disk cleaners and disk space analyzersFAT filesystem and Linux
Linux has several filesystem drivers for the File Allocation Table (FAT) filesystem format. These are commonly known by the names used in the mount command to invoke particular drivers in the kernel: msdos, vfat, and umsdos.File Allocation Table
File Allocation Table (FAT) is a computer file system architecture and a family of industry-standard file systems utilizing it. The FAT file system is a continuing standard which borrows source code from the original, legacy file system and proves to be simple and robust. It offers useful performance even in lightweight 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 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 up to 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. As disk drives evolved, the capabilities of the file system have been extended accordingly, resulting in three major file system variants: FAT12, FAT16 and FAT32. The FAT standard has also been expanded in other ways while generally preserving backward compatibility with existing software.
With the introduction of more powerful computers and operating systems, as well as the development of more complex file systems for them, FAT is no longer the default file system for usage on Microsoft Windows computers.FAT file systems are still commonly found on floppy disks, flash and other solid-state memory cards and modules (including USB flash drives), as well as many portable and embedded devices. FAT is the standard file system for digital cameras per the DCF specification.LOGO.SYS
LOGO.SYS is a core system file used by Windows 9x operating systems to display its boot-up message.
It is present and used in the Windows 95, Windows 98, and Windows ME products. It is not present in the Windows NT family of operating systems, such as Windows XP.
There are three variants of the file:
LOGO.SYS: the "Starting Windows" message, with the Windows logo. The file is located in the root directory of the boot drive. This is usually C:\, but with drive compression, like DriveSpace, this is the host drive (often H:\). The default LOGO.SYS file is also stored in IO.SYS and used by MS-DOS during startup if LOGO.SYS could not be found. The display of the logo can be disabled by adding a LOGO=0 setting to the Options section in the MS-DOS 7 configuration file MSDOS.SYS.
LOGOW.SYS: the "Please wait while Windows is shutting down" message. The file is located in the Windows directory, which by default is C:\WINDOWS. The Windows logo is shown only in Windows 95 and 98. No error will be shown if the file cannot be found.
LOGOS.SYS: the "It is now safe to turn off your computer" message. The file is located in the Windows directory. This message is displayed when Windows has successfully shut down to MS-DOS but is not configured to return to the prompt (COMMAND.COM) again. On systems with proper ACPI support and ATX power supply, the PC may power down instead. If the file cannot be found, the same message is displayed in text mode. No error will be shown if the file cannot be found.LOGO.SYS is in fact an 8-bit RLE-encoded Windows bitmap file with a resolution of exactly 320×400 pixels at 256 colors. This is displayed in the otherwise little-used 320x400 VGA graphics mode, a compromise to allow the display of a 256-color image with high vertical (but not horizontal) resolution on all compatible systems, even those with plain VGA cards (which could only show 16 colors with high horizontal resolution) and without needing any additional graphics drivers. The mode appears, to any attached monitor, to be identical to the more common 640x400 graphics or 720x400 text modes, and is therefore stretched to a standard 4:3 aspect ratio (meaning the pixels appear to be 1.67x (2/1.2) wider than they are tall, instead of square - as they would be on a full 640x480 VGA display) on a typical 4:3 monitor of the time, and on monitors of other shapes (5:4, 16:9, etc.) when set to display standard video modes in their original aspects with letterbox borders. This lent the startup screens a peculiar, characteristic "feel" and made them more suited to certain subjects (which disguised the horizontal blockiness or made good use of the vertical resolution) than others (which accentuated it), meaning some skill was needed in choosing an image that would still be aesthetically pleasing - or even clear enough to be properly interpreted - once resized.
For LOGO.SYS or the equivalent embedded image in IO.SYS, Windows will also animate the image's color information using palette rotation; the image is static, but may have the illusion of movement as colors are changed.
As the files are literally just standard RLE-compressed .BMPs (with an entirely optional custom tag segment) renamed to ".SYS", they may be opened and edited using image editing tools such as MS Paint, and the contents replaced with user-selected pictures; the only conversion needed is to change the file extension, and to ensure they are in the correct resolution and color depth (with dithering if needed). However, the process is not foolproof:
Ensuring the aspect ratio is correct can be confusing, as it is usually displayed in a horizontally compressed form on a screen with square pixels (the most reliable method being to edit at full size, crop to 4:3, then resize to 320x400)
The loading indicator animation was created using palette rotation. The number of palette entries to rotate is determined by the otherwise seldom used biClrImportant field of the BITMAPINFOHEADER structure. Image editing software usually discarded this data, so it was often not possible to retain it. Some logo creation utilities were specifically created to restore the cycling function and allow creating custom animations.
Just like the bootsplash screens in earlier versions of Windows, there was a hard but poorly documented limit on how large the compressed file could be, because of the very limited memory available during the boot process (the very reason that RLE was used in the first place - a plain BMP would have been 125kb and thus entirely too large; the default images are around 10 to 70kb each). If the file was too large, it would either simply fail to display or cause the system to crash, which required the user to reboot and drop into DOS mode before the logo had a chance to load, and either delete it or rename it to prevent the system trying to display it again before it could be fixed or replaced. Staying below, and moreover editing an image to bring it below this limit was an imprecise science that mostly required taking advantage of the particular characteristics of RLE, e.g. ensuring there were sufficient areas of the screen with long horizontal runs of the same color, by reducing the dither quality or color reduction mode, shrinking it slightly and adding a black border a few pixels wide all around, etc. Each run allowed a two byte code to represent a strip many pixels wide, and hence blank spaces or areas of flat color compressed very tightly, whereas regions with no repeated colors at all were at best uncompressed, at worst slightly larger than they would otherwise have been.List of Microsoft Windows components
The following is a list of Microsoft Windows components.List of features removed in Windows XP
As the next version of Windows NT after Windows 2000, as well as the successor to Windows ME, Windows XP introduced many new features but it also removed some others. Following is a list of these.MRCI
MRCI may refer to:
Microsoft Realtime Compression Interface, an optional hardware interface for Microsoft DoubleSpace/DriveSpace
Multireference configuration interaction, a method in quantum chemistryMicrosoft Plus!
Microsoft Plus! is a discontinued commercial operating system enhancement product by Microsoft. The last edition is the Plus! SuperPack, which includes an assortment of screensavers, themes, and games, as well as multimedia applications. The Microsoft Plus! product was first announced on January 31, 1994 under the internal codename "Frosting". The first edition was
an enhancement for Windows 95, Windows 95 Plus!
The enhancements that make up Microsoft Plus! were generally developed by Microsoft itself. The Plus! packs also included games and content from third-party companies; for example, in Plus! for Windows XP, the HyperBowl game developed by Hyper Entertainment Inc. was included. Plus! features that enhance the base operating system or provide utility are generally included free of charge in the next release of Windows.
Microsoft Plus! was discontinued in favor of Windows Ultimate Extras in Windows Vista.QEMM
Quarterdeck Expanded Memory Manager (QEMM) is a memory manager produced by Quarterdeck Office Systems in the late 1980s through late 1990s. It was the most popular third-party memory manager for the MS-DOS and other DOS operating systems.Star Drive
Star Drive (stylized as Star*Drive) is a science fiction campaign setting that was published in 1998 by TSR, Inc. for the Alternity role-playing game. Alternity's first setting was detailed in the Star Drive Campaign Setting (1998).It was written by David Eckelberry and Richard Baker. This setting book also requires the Player's Handbook and Gamemaster Guide for the Alternity game system. Much of the material created for this campaign setting was later reused in the d20 Future supplement of the d20 Modern role-playing game.Windows 95
Windows 95 (codenamed Chicago) 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 manufacturing on August 15, 1995, and generally to retail on August 24, 1995. Windows 95 merged Microsoft's formerly separate MS-DOS and Windows products, and featured significant improvements over its predecessor, most notably in the graphical user interface (GUI) and in its simplified "plug-and-play" features. There were also major changes made to the core components of the operating system, such as moving from a mainly co-operatively multitasked 16-bit architecture to a 32-bit preemptive multitasking architecture.
Accompanied by an extensive marketing campaign, Windows 95 introduced numerous functions and features that were featured in later Windows versions, such as the taskbar, the "Start" button and the ways the user could navigate.Three years after its introduction, Windows 95 was succeeded by Windows 98. Microsoft ended extended support for Windows 95 on December 31, 2001.Windows 98
Windows 98 (codenamed Memphis) is a graphical operating system developed by Microsoft as part of its Windows 9x family of operating systems. It is the successor to Windows 95, and was released to manufacturing on May 15, 1998, and to retail on June 25, 1998. Like its predecessor, Windows 98 is a hybrid 16-bit and 32-bit monolithic product with the boot stage based on MS-DOS. The startup sound for Windows 98 was composed by Microsoft sound engineer Ken Kato, who considered it to be a "tough act to follow".Windows 98 was succeeded by Windows 98 Second Edition (SE) on May 5, 1999, which, in turn, was succeeded by Windows ME on September 14, 2000. Microsoft ended mainstream support for both Windows 98 and 98 SE on June 30, 2002, and extended support on July 11, 2006.Windows ME
Windows Millennium Edition, or Windows ME (marketed with the pronunciation of the pronoun "me" and codenamed Millennium), is a graphical operating system developed by Microsoft as part of its Windows 9x family of operating systems. It is the successor to Windows 98, and was released to manufacturing on June 19, 2000, with general availability on September 14, 2000.
Windows ME was the last operating system released in the Windows 9x series which was targeted specifically at home PC users, and included Internet Explorer 5.5, Windows Media Player 7, and the new Windows Movie Maker software, which provided basic video editing and was designed to be easy to use for home users. Microsoft also updated the graphical user interface, shell features, and Windows Explorer, with some of those first introduced in Windows 2000, which had been released as a business-oriented operating system seven months earlier. Windows ME could be upgraded to Internet Explorer 6 SP1 (but not to SP2 (SV1) or Internet Explorer 7), Outlook Express 6 SP1 and Windows Media Player 9 Series. Microsoft .NET Framework up to and including version 2.0 is supported; however, versions 2.0 SP1, 3.x, and greater are not. Office XP was the last version of Microsoft Office to be compatible with Windows ME.
Windows ME was a continuation of the Windows 9x model and still DOS-based like its predecessors, but with restricted access to real mode MS-DOS in order to decrease system boot time. In 2001, Windows XP was released and became Windows ME's successor, popularizing most of its features and introducing more visual themes.XB Machine
xB Machine has been a virtual operating system that was small enough to fit on a USB drive. The last version seems to have been 0.9.1.5 in mid of 2008. It brought a secure computing environment that anonymized all internet activity, and had portable encrypted file storage. It had been developed and offered by XeroBank and based on a modified Gentoo Linux distribution. It could be executed as a virtual machine through a QEMU hypervisor, VMWare, VirtualBox, and any other major virtualization system. It could also be booted from on USB or burned to CD for booting. Virtualization, along with the native implementation of a Tor onion routing for internet connectivity and other encryption and privacy tools, had been utilized to increase the security and anonymity of the user.
The developers claimed that it is the most secure operating system in the world
and that the technology involved is highly resistant to hacking and spying, even in the most hostile environments. The details and transactions inside each xB Machine account were protected with 256-bit AES encryption. The software also had a self-destruct sequence for eliminating any traces that a user may have left behind on the drivespace after using xB Machine. Meanwhile, Xerobank offers a modular package with xB Browser, xB Mail, and xB VPN, parts of it running only for customers of the bank.
Features of XB Machine have been:
LiveCD or bootable ISO on Windows, Linux and Mac OS X
VMware detection and support
KQEMU accelerator kernel module
Includes xB Browser (Firefox with inbuilt Tor network)
Includes xB Mail (generic Thunderbird ATM)
Torrent support via cTorrent