Prerequisites
Install Iverilog and GTKWave from http://iverilog.icarus.com/, http://gtkwave.sourceforge.net/
- or
apt install iverilog gtkwave
Commands
$ git clone https://github.com/sarthak7gupta/VerilogAdderSubtractor16bit.git
$ cd VerilogAdderSubtractor16bit
$ iverilog -o vas PrefixAddSub16.v PrefixAddSub16_tb.v
$ vvp vas
$ gtkwave testbench.vcd &