Ctags is a programming tool that generates an index (or tag) file of names found in source and header files of various programming languages to aid code comprehension. Depending on the language, functions, variables, class members, macros and so on may be indexed. These tags allow definitions to be quickly and easily located by a text editor, a code search engine, or other utility. Alternatively, there is also an output mode that generates a cross reference file, listing information about various names found in a set of language files in human-readable form.