[[Property:title|Using libraries]]
[[Property:weight|5]]
[[Property:uuid|443320fa-8e5c-fd13-ed20-66e49094f3d5]]
There are two kinds of libraries in Eiffel: precompiled Eiffel libraries and C libraries.

To use an Eiffel precompiled library:
* Open the [[Group Options|Project Settings]]  dialog. 
* Add a new precompile group to your target.
* You must [[Generating executables|recompile]]  your project from scratch for the changes to take effect. 

{{note|You can only use one precompiled library at a time in a project. To use more than one, you should precompile all the libraries you want to use together in a single precompiled library. }}

To use a C library:
* Open the [[Externals Options|Project Settings]]  dialog. 
* Add an include external for the directory where the header files needed to use the library are.
* Add an object external for each object file needed to use the library. These files can be either library files (.lib, .a, etc) or object files (.obj, .o, etc) 
* Click '''OK'''. 
* You must [[Generating executables|recompile]]  your project for the changes to take effect. 

{{seealso|<br/>
[[Generating libraries|Creating libraries]]  <br/>
[[Adding a cluster|Adding classes and clusters from Eiffel libraries without precompiling the library]]  <br/>
[[C externals|Making C calls in Eiffel]]  }}