Wikipedia
ACDSee, ACDSee Pro and ACDSee Free are image organizer, viewer, and RAW / image editor programs for Microsoft Windows and Mac OS X 10.6 and higher, developed by ACD Systems International Inc. ACDSee was originally distributed as a 16-bit application for Windows 3.0 and later supplanted by a 32-bit version for Windows 95. ACDSee Pro 6 adds native 64-bit support.
ACDSee's main competitors are Adobe's Photoshop Lightroom and Apple's Aperture.
ACDSee's main features are speed, lossless RAW/image editing, image batch processing, metadata ( Exif/ IPTC), with support to edit/embed metadata in image files, rating, keywords, and categories, and geotagging/ GPS support. Judging the image quality of a picture is fast due to next/previous image caching, fast image/RAW decoding and support for one-click toggling between 100% and fit screen zoom mode anywhere inside the image. For professional users most of ACDSee's features can be accessed via keyboard.
ACDSee displays a tree view of the file structure for navigation with thumbnail images of the selected folder, and a preview of a selected image. ACDSee started as an image organizer/viewer, but over time had image editing and RAW development (Pro version) capabilities added. The thumbnails generated by ACDSee are cached so that they do not need to be regenerated.
Unlike programs such as Adobe Lightroom, ACDSee only stores image metadata in its database. Lightroom stores the changes made to images in its database also, not affecting the files on disk. ACDSee's database can be backed up, and exported/imported as XML or binary.
The photo manager is available as a consumer version, and a pro version which provides additional features, and additional image editing capabilities. In 2012, ACDSee Free was released, without advanced features.