There are fixed and programmable FPGA devices.

• VSLI (Very Large Scale Integration)

Lookup Tables (LUTs)

In an FPGA logic cell/block, there is an n-input LUT that serves as a $2^n$ address memory

The DE1 and DE0 boards use 4-input LUTs

Multiplexers (Muxes)

Multiplexers allow the routing of inputs to an output to be controlled by a signal