DEF File Extension

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

What is the .DEF file type?

The DEF file extension is attributed to module definition files saved in a plain text format. DEF was developed by Cadence Design Systems for programs created via Microsoft Visual C++ as well as other C++ software development tools.

DEF files are normally used when building a dynamic link library (DLL) for various software applications. Their aim is to provide the application linker with data on attributes, exports, etc. of different modules or libraries and connect a large number of components.

Typically, .def files have at least two sections. The first one is the LIBRARY statement that takes just one line. It is used to indicate that the .def file belongs to some particular DLL. The second one is the EXPORTS statement that contains the list of the functions and possible ordinal values of each function that will be exported by the DLL.

DEF file are necessary if the software developer doesn't use _declspec or _dllexport export functions. A .def file is typically accompanied by a matching .lef file to represent all required information about the components in an ASCII format.

Software to open or convert DEF files

You can open DEF files with the following programs: 

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