DiskDoubler
Encyclopedia
DiskDoubler is a data compression
utility for compressing file
s on the Apple Macintosh platform. Unlike most such programs, which compress numerous files into a single archive for transmission, DiskDoubler was intended to compress single files "in place" to save space on the drive. When such a file was opened, DiskDoubler would decompress the file before handing it off to the application for use. A later addition, AutoDoubler, added background compression, finding and compressing files automatically when the computer was idle.
DiskDoubler was created by Terry Morse and Lloyd Chambers, fellow employees at a small software firm that went out of business in 1989. Chambers had already released a version of the Unix
Compress
utility on the Mac as MacCompress, and while working on another "real" project, Chambers wrote DiskDoubler in his spare time. When demonstrating their new product at a local Mac store, they noticed that it was DiskDoubler that got all of the attention. It was first shown publicly at the San Francisco MacWorld Expo in April 1990 (normally in January, but delayed that year) and by the end of the show had sold 500 copies. By the summer they were selling 1000 copies a month.
Realizing they needed real marketing muscle, they approached Symantec
, who agreed to include it in their Symantec Utilities for Macintosh (SUM) package for a pittance. Unimpressed by the offer, they instead asked Guy Kawasaki
to front them a $25,000 development loan, raised a similar amount on their own, and formed Salient Software. After four months sales were over $50,000 a month. When System 7
shipped in June 1991 sales took off, as the new system was rather hungry for drive space. The company was eventually sold to Fifth Generation Systems in 1992. They also repackaged it in a suite as SuperDoubler 4.0, including AutoDoubler, DiskDoubler, and a file-copy speedup known as CopyDoubler. For some time, DiskDoubler was the second-best selling product on the Mac, second only to After Dark, the popular screen saver. Fifth Generation was later sold, somewhat ironically, to Symantec, who re-released it as a fat binary
as Norton DiskDoubler Pro 1.1. Symantec "sat" on the product and it slowly disappeared over the next year.
DiskDoubler concentrated on speed, originally supporting only a single variety of the LZ78 compression algorithm used in Compress/MacCompress to avoid having to try different settings. Nevertheless the compression results were quite reasonable, notably on text files. Better yet, DiskDoubler was extremely fast, generally twice as fast as StuffIt
, and 50% faster than Compact Pro
, the two main archivers in use on the Mac in the 1990s. DiskDoubler also had the capability of decompressing StuffIt and PackIt
files, which it did much faster than those programs could. Over the years DiskDoubler eventually ended up with four different algorithms, typically using the fastest compressor, DD1, for a first pass, and then running the most effective, DD3+, when the machine was idle. DiD3+ provided the highest compression of any Mac-based compression software, using knowledge of specific file types to improve over a "generic" LZW
scheme.
Users typically interacted with DiskDoubler via an additional menu placed in the Macintosh Finder
. Selecting a file, or group of them, the user selects Compress from the DD menu. The file in question is quickly compressed and replaced by a similar icon stamped with a small "DD" tag to indicate it was compressed. The original Mac OS
did not include any sort of composite icon support, so DiskDoubler had to copy and modify every icon it found and then hand those modified icons back to the Finder with a new file type. When a file was compressed, its (hidden) file type flag was changed to the one DiskDoubler "made up", making the Finder display the modified icon.
AutoDoubler (AD) was a small software daemon
for which speed was the main concern, since AD was intended to be used "invisibly". For this reason it first used the AD1/DD1 "fastest" method to compress as many files as possible as quickly as it could, and then when that was complete it would go back and re-compress with DD3+ if the machine was still idle. DD/AD was so invisible that it would compress anything outside the System folder, including applications and various resources.
The product also included a freeware
(but closed source) decompressor known as DDExpand. Since DiskDoubler was intended to compress "in place" and generally be invisible, most users set up DiskDoubler to decompress automatically when copying files to other media so that it would open fine on other people's machines. Additionally, since the program decompressed files as they were opened, the simple action of archiving files using another utility like StuffIt automatically decompressed the files before they were inserted into the new archive. For these reasons the DiskDoubler format was rarely seen "in the wild", and DDExpand was rarely needed. DiskDoubler did include an option for this, however, which would combine several files into one archive. These could sometimes be found in software libraries, but was generally frowned upon.
DiskDoubler created a market for similar products. The first attempt to produce a similar product resulted in SuperDisk!, which, when released, was faster than DiskDoubler but offered less compression. SuperDisk! also offered "on the fly" compression, which DiskDoubler had not added at that point. An updated version of DiskDoubler fought back with a new compression scheme that ran entirely in the 256-byte cache of the 68020, which greatly improved performance. AutoDoubler was also included as a new feature. Now Software
also introduced a product in this space: Now Compress. Aladdin eventually brought out their own solution as well, StuffIt SpaceSaver. All of these products had a following during the era of small hard drives.
Eventually, a combination of shrinking Mac marketshare, changes to the underlying filesystem and ever-increasing drive space killed off this product niche.
Data compression
In computer science and information theory, data compression, source coding or bit-rate reduction is the process of encoding information using fewer bits than the original representation would use....
utility for compressing file
Computer file
A computer file is a block of arbitrary information, or resource for storing information, which is available to a computer program and is usually based on some kind of durable storage. A file is durable in the sense that it remains available for programs to use after the current program has finished...
s on the Apple Macintosh platform. Unlike most such programs, which compress numerous files into a single archive for transmission, DiskDoubler was intended to compress single files "in place" to save space on the drive. When such a file was opened, DiskDoubler would decompress the file before handing it off to the application for use. A later addition, AutoDoubler, added background compression, finding and compressing files automatically when the computer was idle.
DiskDoubler was created by Terry Morse and Lloyd Chambers, fellow employees at a small software firm that went out of business in 1989. Chambers had already released a version of the Unix
Unix
Unix is a multitasking, multi-user computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs, including Ken Thompson, Dennis Ritchie, Brian Kernighan, Douglas McIlroy, and Joe Ossanna...
Compress
Compress
Compress is a UNIX compression program based on the LZC compression method, which is an LZW implementation using variable size pointers as in LZ78.- Description of program :Files compressed by compress are typically given the extension .Z...
utility on the Mac as MacCompress, and while working on another "real" project, Chambers wrote DiskDoubler in his spare time. When demonstrating their new product at a local Mac store, they noticed that it was DiskDoubler that got all of the attention. It was first shown publicly at the San Francisco MacWorld Expo in April 1990 (normally in January, but delayed that year) and by the end of the show had sold 500 copies. By the summer they were selling 1000 copies a month.
Realizing they needed real marketing muscle, they approached Symantec
Symantec
Symantec Corporation is the largest maker of security software for computers. The company is headquartered in Mountain View, California, and is a Fortune 500 company and a member of the S&P 500 stock market index.-History:...
, who agreed to include it in their Symantec Utilities for Macintosh (SUM) package for a pittance. Unimpressed by the offer, they instead asked Guy Kawasaki
Guy Kawasaki
Guy Kawasaki is a Silicon Valley venture capitalist, bestselling author, and Apple Fellow. He was one of the Apple employees originally responsible for marketing the Macintosh in 1984. He is currently a Managing Director of Garage Technology Ventures, and has been involved in the rumor reporting...
to front them a $25,000 development loan, raised a similar amount on their own, and formed Salient Software. After four months sales were over $50,000 a month. When System 7
System 7 (Macintosh)
System 7 is a single-user graphical user interface-based operating system for Macintosh computers. It was introduced on May 13, 1991 by Apple Computer. It succeeded System 6, and was the main Macintosh operating system until it was succeeded by Mac OS 8 in 1997...
shipped in June 1991 sales took off, as the new system was rather hungry for drive space. The company was eventually sold to Fifth Generation Systems in 1992. They also repackaged it in a suite as SuperDoubler 4.0, including AutoDoubler, DiskDoubler, and a file-copy speedup known as CopyDoubler. For some time, DiskDoubler was the second-best selling product on the Mac, second only to After Dark, the popular screen saver. Fifth Generation was later sold, somewhat ironically, to Symantec, who re-released it as a fat binary
Fat binary
A fat binary is a computer program with code native to multiple Instruction sets which can consequently be run on multiple processor types. The usual method of implementation is to include a version of the machine code for each instruction set, preceded by code compatible with all operating...
as Norton DiskDoubler Pro 1.1. Symantec "sat" on the product and it slowly disappeared over the next year.
DiskDoubler concentrated on speed, originally supporting only a single variety of the LZ78 compression algorithm used in Compress/MacCompress to avoid having to try different settings. Nevertheless the compression results were quite reasonable, notably on text files. Better yet, DiskDoubler was extremely fast, generally twice as fast as StuffIt
StuffIt
StuffIt is a family of computer software utilities for archiving and compressing files on the Macintosh and Microsoft Windows platforms: it was originally produced for the Macintosh. An old version for Linux and Sun Solaris 2.7 or later is also available...
, and 50% faster than Compact Pro
Compact Pro
Compact Pro is a software data compression utility for archiving and compressing files on the Apple Macintosh platform. It was a major competitor to StuffIt in the early 1990s, producing smaller archives in less time, as well as being distributed via shareware which greatly helped its popularity...
, the two main archivers in use on the Mac in the 1990s. DiskDoubler also had the capability of decompressing StuffIt and PackIt
PackIt
PackIt is a software data compression utility for archiving and compressing files on the Apple Macintosh platform. It was the first such program to see widespread use on the Mac, and most Mac software archives accepted uploads only in PackIt format for some time...
files, which it did much faster than those programs could. Over the years DiskDoubler eventually ended up with four different algorithms, typically using the fastest compressor, DD1, for a first pass, and then running the most effective, DD3+, when the machine was idle. DiD3+ provided the highest compression of any Mac-based compression software, using knowledge of specific file types to improve over a "generic" LZW
LZW
Lempel–Ziv–Welch is a universal lossless data compression algorithm created by Abraham Lempel, Jacob Ziv, and Terry Welch. It was published by Welch in 1984 as an improved implementation of the LZ78 algorithm published by Lempel and Ziv in 1978...
scheme.
Users typically interacted with DiskDoubler via an additional menu placed in the Macintosh Finder
Macintosh Finder
The Finder is the default file manager used on Mac OS and Mac OS X operating systems; it is responsible for the overall user-management of files, disks, network volumes and the launching of other applications...
. Selecting a file, or group of them, the user selects Compress from the DD menu. The file in question is quickly compressed and replaced by a similar icon stamped with a small "DD" tag to indicate it was compressed. The original Mac OS
Mac OS
Mac OS is a series of graphical user interface-based operating systems developed by Apple Inc. for their Macintosh line of computer systems. The Macintosh user experience is credited with popularizing the graphical user interface...
did not include any sort of composite icon support, so DiskDoubler had to copy and modify every icon it found and then hand those modified icons back to the Finder with a new file type. When a file was compressed, its (hidden) file type flag was changed to the one DiskDoubler "made up", making the Finder display the modified icon.
AutoDoubler (AD) was a small software daemon
Daemon (computer software)
In Unix and other multitasking computer operating systems, a daemon is a computer program that runs as a background process, rather than being under the direct control of an interactive user...
for which speed was the main concern, since AD was intended to be used "invisibly". For this reason it first used the AD1/DD1 "fastest" method to compress as many files as possible as quickly as it could, and then when that was complete it would go back and re-compress with DD3+ if the machine was still idle. DD/AD was so invisible that it would compress anything outside the System folder, including applications and various resources.
The product also included a freeware
Freeware
Freeware is computer software that is available for use at no cost or for an optional fee, but usually with one or more restricted usage rights. Freeware is in contrast to commercial software, which is typically sold for profit, but might be distributed for a business or commercial purpose in the...
(but closed source) decompressor known as DDExpand. Since DiskDoubler was intended to compress "in place" and generally be invisible, most users set up DiskDoubler to decompress automatically when copying files to other media so that it would open fine on other people's machines. Additionally, since the program decompressed files as they were opened, the simple action of archiving files using another utility like StuffIt automatically decompressed the files before they were inserted into the new archive. For these reasons the DiskDoubler format was rarely seen "in the wild", and DDExpand was rarely needed. DiskDoubler did include an option for this, however, which would combine several files into one archive. These could sometimes be found in software libraries, but was generally frowned upon.
DiskDoubler created a market for similar products. The first attempt to produce a similar product resulted in SuperDisk!, which, when released, was faster than DiskDoubler but offered less compression. SuperDisk! also offered "on the fly" compression, which DiskDoubler had not added at that point. An updated version of DiskDoubler fought back with a new compression scheme that ran entirely in the 256-byte cache of the 68020, which greatly improved performance. AutoDoubler was also included as a new feature. Now Software
Now Software
Now Software was the producer of Now Up-to-Date & Contact, a software calendar and contact manager for individuals and groups. On August 27, 2009, the company released Now X, the successor to Now Up-to-Date & Contact....
also introduced a product in this space: Now Compress. Aladdin eventually brought out their own solution as well, StuffIt SpaceSaver. All of these products had a following during the era of small hard drives.
Eventually, a combination of shrinking Mac marketshare, changes to the underlying filesystem and ever-increasing drive space killed off this product niche.
External links
- Review: Norton DiskDoubler Pro 1.1
- macutils, converts between different Macintosh file encodings; supposedly can unpack DiskDoubler archives
- DiskDoubler Pro 4.1 for Mac OS 9