ModelSim is a multi-language HDL simulation environment by Mentor Graphics, for simulation of hardware description languages such as VHDL, Verilog and SystemC, and includes a built-in C debugger. ModelSim can be used independently, or in conjunction with Altera Quartus or Xilinx ISE. Simulation is performed using the graphical user interface (GUI), or automatically using scripts. 
ModelSim SE offers high-performance and advanced debugging capabilities, while ModelSim PE is the entry-level simulator for hobbyists and students. ModelSim SE is used in large multi-million gate designs, and is supported on Microsoft Windows and Linux, in 32-bit and 64-bit architectures.
ModelSim XE stands for Xilinx Edition, and is specially designed for integration with Xilinx ISE. ModelSim XE enables testing of HDL programs written for Xilinx Virtex/Spartan series FPGA's without needed physical hardware.
ModelSim can also be used with MATLAB/Simulink, using Link for ModelSim. Link for ModelSim is a fast bidirectional co-simulation interface between Simulink and ModelSim. For such designs, MATLAB provides a numerical simulation toolset, while ModelSim provides tools to verify the hardware implementation & timing characteristics of the design.
ModelSim uses a unified kernel for simulation of all supported languages, and the method of debugging embedded C code is the same as VHDL or Verilog.
ModelSim enables simulation, verification and debugging for the following languages:
- Handbook of Digital Techniques for High-Speed Design, Pearson Education India, 01-Sep-2007
- Reconfigurable Embedded Control Systems, Idea Group Inc (IGI), 30-Nov-2010
- Digital Hardware Design, Laxmi Publications, Ltd., 01-Sep-2008
- Synthesizable VHDL Design for FPGAs, Springer Science & Business Media, 21-Oct-2013
- Modern Automation Systems, Laxmi Publications, Ltd., 01-May-2009
- Industrial Control Technology, William Andrew, 12-Aug-2008
- Recent Advances in Modeling and Simulation Tools for Communication Networks and Services, Springer Science & Business Media, 20-Sep-2007