So the code instructs the FPGA (or, more accurately, the Verilog compiler) to examine the number and set dispoutput based on the input. The <= character, by the way, are a non-blocking assignment.

This paper focuses on the implementation and simulation of 4-bit, 8-bit and 16-bit carry look-ahead adder based on Verilog code and compared for their performance in Xilinx.