DiskDoubler (DD) is a
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 compression ...
utility for compressing
file
File or filing may refer to:
Mechanical tools and processes
* File (tool), a tool used to ''remove'' fine amounts of material from a workpiece
**Filing (metalworking), a material removal process in manufacturing
** Nail file, a tool used to gent ...
s on the
Apple Macintosh
The Mac (known as Macintosh until 1999) is a family of personal computers designed and marketed by Apple Inc. Macs are known for their ease of use and minimalist designs, and are popular among students, creative professionals, and software en ...
platform. Unlike most such programs, which compresses numerous files into a single archive for transmission, DiskDoubler is intended to compress single files "in place" to save space on the drive. When such a file is opened, DiskDoubler decompresses the file before handing it off to the application for use. A later addition, AutoDoubler, adds 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 (; trademarked as UNIX) is a family of multitasking, multiuser computer operating systems that derive from the original AT&T Unix, whose development started in 1969 at the Bell Labs research center by Ken Thompson, Dennis Ritchie, and ot ...
Compress
compress is a Unix shell compression program based on the LZW compression algorithm. Compared to more modern compression utilities such as gzip and bzip2, compress performs faster and with less memory usage, at the cost of a significantly lo ...
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
Macworld/iWorld was an information technology trade show with conference tracks dedicated to the Apple Macintosh platform. It was held annually in the United States during January. Originally ''Macworld Expo'' and then ''Macworld Conference & Expos ...
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
Guy Kawasaki (born August 30, 1954) is an American marketing specialist, author, and Silicon Valley venture capitalist. He was one of the Apple employees originally responsible for marketing their Macintosh computer line in 1984. He popularized ...
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, codenamed "Big Bang", and also known as Mac OS 7, is a graphical user interface-based operating system for Macintosh computers and is part of the classic Mac OS series of operating systems. It was introduced on May 13, 1991, by Apple Co ...
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
Fifth Generation Systems, Inc., was a computer security company founded October 1984 in Baton Rouge, Louisiana, United States by Robert Mitchell, Leroy Mitchell, Roger Ivey, and Bruce Ray. All four later left the company. Fifth Generation's initi ...
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
A fat binary (or multiarchitecture binary) is a computer executable program or library which has been expanded (or "fattened") with code native to multiple instruction sets which can consequently be run on multiple processor types. This results ...
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
LZ77 and LZ78 are the two lossless data compression algorithms published in papers by Abraham Lempel and Jacob Ziv in 1977 and 1978.
They are also known as LZ1 and LZ2 respectively. These two algorithms form the basis for many variations includi ...
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
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, able to create self-extract ...
, the two main archivers in use on the Mac in the 1990s. DiskDoubler also had the capability of decompressing StuffIt and
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 ...
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
The Finder is the default file manager and graphical user interface shell used on all Macintosh operating systems. Described in its "About" window as "The Macintosh Desktop Experience", it is responsible for 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
Classic Mac OS
Mac OS (originally System Software; retronym: Classic Mac OS) is the series of operating systems developed for the Macintosh family of personal computers by Apple Computer from 1984 to 2001, starting with System 1 and ending with Mac OS 9. The ...
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 main reason for better performance was the fact that compressing a file and writing it was faster than writing the original file as the bottleneck was to be found in hard disk I/O times. The same is correct for reading and decompressing files.
The product also included a
freeware
Freeware is software, most often proprietary, that is distributed at no monetary cost to the end user. There is no agreed-upon set of rights, license, or EULA that defines ''freeware'' unambiguously; every publisher defines its own rules for the f ...
(but
closed source
Proprietary software is software that is deemed within the free and open-source software to be non-free because its creator, publisher, or other rightsholder or rightsholder partner exercises a legal monopoly afforded by modern copyright and inte ...
) 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
The Motorola 68020 ("''sixty-eight-oh-twenty''", "''sixty-eight-oh-two-oh''" or "''six-eight-oh-two-oh''") is a 32-bit microprocessor from Motorola, released in 1984. A lower-cost version was also made available, known as the 68EC020. In keepin ...
, which greatly improved performance. AutoDoubler was also included as a new feature.
Now Software
__NOTOC__
Now Software was the producer of Now Up-to-Date & Contact, a calendaring software and contact manager for individuals and groups, for macOS and Windows. The company was incorporated in 1989.
Now Software, then based in Portland, Oregon, ...
also introduced a product in this space called Now Compress. Aladdin Software eventually brought out their own solution as well, as StuffIt SpaceSaver. All of these products had a following during the era of small
hard drive
A hard disk drive (HDD), hard disk, hard drive, or fixed disk is an electro-mechanical data storage device that stores and retrieves digital data using magnetic storage with one or more rigid rapidly rotating platters coated with magnet ...
s.
Eventually, a combination of shrinking Mac marketshare, changes to the underlying filesystem and ever-increasing drive space killed off this product niche.
With the introduction of
Mac OS X Snow Leopard
Mac OS X Snow Leopard (version 10.6) is the seventh major release of macOS, Apple's desktop and server operating system for Macintosh computers.
Snow Leopard was publicly unveiled on June 8, 2009 at Apple’s Worldwide Developers Conference. ...
, Apple introduced a similar technology known as Transparent Compression into
HFS Plus
HFS Plus or HFS+ (also known as Mac OS Extended or HFS Extended) is a journaling file system developed by Apple Inc. It replaced the Hierarchical File System (HFS) as the primary file system of Apple computers with the 1998 release of Mac OS ...
.
See also
*
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 ...
References
* Guy Kawasaki
"Defying Gravity" ''Macworld'', December 1993
* E-mail conversations with both of the original authors.
External links
Review: Norton DiskDoubler Pro 1.1macutils converts between different Macintosh file encodings; supposedly can unpack DiskDoubler archives
Classic Mac OS software
Data compression software
1990 software
Discontinued software