The .x file extension is most commonly associated with Lex source code files. These files contain source code that has been written in the Lex programming language. The X files can be used to create a C program using a lex utility that is included with most Unix distributions.
The .x file extension is also used for Alysis SuperDisk self-extracting archive files, Microsoft Direct-X SDK files, Stardent AVS X bitmap image files, X-file animation file Direct3D files, FPS Creator Model files, Chemical modeller output files, XBLite program files and X11 server import image files.
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File.org aims to be the go-to resource for file type- and related software information. We spend countless hours researching various file formats and software that can open, convert, create or otherwise work with those files.
If you have additional information about the X file format or software that uses files with the X suffix, please do get in touch - we would love hearing from you.