Words that are reserved for implementing syntax in files used as inputs to the Quartus^® II software. Such files include AHDL Text Design Files (.tdf), VHDL Design Files (.vhd), Verilog Design Files (.v), Project Configuration Files (.quartus), Entity Settings Files (.esf), Compiler Settings Files (.csf), and Simulator Settings Files (.ssf). For example, the keyword OF is reserved in AHDL files, and therefore cannot be used as an unquoted symbolic name in an TDF File.