An Introduction To VHDL:

The Theory
           The power of the FPGA/CPLD is that we can design our own custom 'IC' (integrated circuit), if you will, to accomplish a task instead of combining together several other pre-existing IC's. Here is the 'circuit' in schematic for that we will build using VHDL software:

           You can see how the entire circuit is made of standard logic gates; encoders, or gates & mux's. The input is given from the DIP_Switches and Output to the LEDS. After building the vhdl program you can see this exact schematic in quartus II, just go to Tools -> Netlist Viewers -> RTL Viewer.