Add-ons
The company 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 as well as support for background defragmentation of DoubleSpace compressed drives. Optionally, it was possible to let DoubleTools replace the low-level DoubleSpace driver (DBLSPACE.BIN) with one supplied by DoubleTools, enabling enhanced functionality of the product.
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 and, consequently, space savings.
Other products, like later versions of Stacker from Stac Electronics, were capable of converting existing DoubleSpace compressed drives into the Stacker format.
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