Opening 51 files

Have a problem opening a .51 file? We collect information about file formats and can explain what 51 files are. Additionally we recommend software suitable for opening or converting such files.

What is the .51 file type?

The occurrence of numerical indexes like .51 in the role of a filename extension relates primarily to the versioned project backup files created in Pro/Engineer, an exceedingly powerful and complex parametric CAD system from PTC. Pro/Engineer addresses precision design needs in a number of technology-reliant industries.

In Pro/Engineer, a system of automatic versioned backups is maintained, in order to safeguard user data and provide traceability. Every time the current project is changed, but before any changes are committed, its copy is saved into a file with an additional numerical extension like .51. Thus, the .51 file is the fifty-first copy of an actively edited Pro/Engineer project. Pro/Engineer recognizes versioned backups by their indexes and treats them accordingly.

Since dotted numerical indexes are commonly used in filenames to reflect a file's position within a series, a trailing index like .51 can easily become an interim extension, if the original extension is somehow missing. If the correct file type is known, a proper extension should be added manually. Otherwise, one can get clues about the file type/format from the 'magic number' in the file's header.

In Microsoft Windows, the true extension can simply be hidden through the "Hide extensions for known file types" option (on by default). To avoid confusion, this option should always be off.

Apart from that, numerical suffixes like .51 are used to designate volumes of split files. A split file is usually a large file broken down into multiple parts, with each part a separate file (volume) whose numeric index denotes its place in the joining sequence. Before a split file can be used as a whole, all its parts must be present and rejoined with one of multiple file splitting/joining tools.

Software to open or convert 51 files

You can open 51 files with the following programs:
3D-Tool by 3D-Tool GmbH & Co. KG
3D-Tool by 3D-Tool
Photo Gallery
Photo Gallery by Microsoft Corporation

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