<p>What is the difference between using angle brackets and quotes in an <code>include</code> directive?</p>
<ul>
<li><code>#include &lt;filename&gt;</code></li>
<li><code>#include &quot;filename&quot;</code></li>
</ul>

What differs is the locations in which the preprocessor searches for the file to be included.
```
#include <filename>
```
The preprocessor searches in an implementation-defined manner, normally in directories pre-designated by the compiler/IDE. This method is normally used to include header files for the C standard library and other header files associated with the target platform.
```
#include "filename"
```
The preprocessor also searches in an implementation-defined manner, but one that is normally used to include programmer-defined header files and typically includes same directory as the file containing the directive (unless an absolute path is given).
For GCC, a more complete description is available in the GCC
documentation on search paths
.