This document contains Verilog code for several basic digital logic components: a 4:1 multiplexer, JK flip-flop, 4-to-2 encoder, 2-to-4 decoder, 1:4 demultiplexer, asynchronous counter that counts from 0-3 repeatedly, and a skipping counter that counts 0-1-3-0 repeatedly. Each component is defined in a separate module with inputs, outputs, and logic assignments to implement the desired function.