The standard C/C++ editor is provided by the CDT plug-in that provides C and C++ extensions to the workbench. It provides syntax highlighting, formatting of code and content assistance when editing C/C++ code. See the C/C++ Development User Guide in the dynamic help for more information.

If this is not the default editor, right-click on a source file in the Project Explorer view and select Open With → C/C++ Editor from the context menu.