i hope you are talking about VCD -Value change dump file...
A VCD file is an ASCII file that contains header information, variable definitions, and the value changes for all variables specified in the task calls.
Several system tasks can be inserted in the source description to create and control the VCD file.
This is a STANDARD format and is compatible between different waveform viewers etc. Also most of the simulators can write out VCD files - both VHDL & Verilog versions.