FPGA vendors provide design software that support their devices. It does four main things:
There are usually two versions: one free that supports low to medium density FPGA devices, and a full (non-free) version of the same software for big devices.
The free software is usually fine to start with because it is similar in functionality to the full version, and today's low to medium density devices are very capable.
Here's a summary of the features/limitations of the software:
|Design-entry||VHDL, Verilog, ABEL, Schematic, EDIF||VHDL, Verilog, SystemVerilog, AHDL, Schematic, EDIF|
|Core generator||Yes (CORE Generator)||Yes (MegaWizard Plug-Ins)|
|Functional simulation||No||No (last version with simulation was 9.1SP2)|
|Testbench simulation||Use ISim||Use ModelSim-Altera Starter Edition|
|Synthesis/P&R||Free version limited to small & medium devices||Free version limited to small & medium devices|
|FPGA editor||Yes (FPGA editor)||Yes (Chip Editor)|
|Embedded logic analyzer||ChipScope PRO (a separate product - not free)||SignalTap II (included in Quartus II Web/Lite edition)|
|Older versions||Available from ISE Classics||Available from the Quartus II Software Archive|
|OS support||Windows + Linux||Windows + Linux|
|Price||Free version: $0|
Full version: starting at $2995 for a 12 month license
|Free version: $0|
Full version: $2995 for a 12 month license
|Software matrix||Check here||Check here|
As of this writing (May 2013), Quartus-II is better overall - it runs faster, has a better GUI, better HDL support and includes one killer feature: SignalTap II embedded logic analyzer, which is easy to use and available in the free edition. Altera's low point is their simulator - they dropped their own integrated simulator but didn't have anything to replace it so rely on ModelSim for now.
Xilinx traditionally had better silicon, and Altera better software... this seems to still hold true.