Ctags parses source code and produces a sort of index mapping the names of significant entities (e.g. functions, classes, variables) to the location where that entity is defined. This index is used by editors like vi and emacsen to allow moving to the definition of a user-specified entity.

Exuberant Ctags supports all possible C language constructions and multiple other languages such as assembler, AWK, ASP, BETA, Bourne/Korn/Z shell, C++, COBOL, Eiffel, Fortran, Java, Lisp, Lua, Makefile, Pascal, Perl, PHP, Python, REXX, Ruby, S-Lang, Scheme, Tcl, Verilog, Vim and YACC.