People always say to be careful not to derefrence a pointer that points to address 0 because then your program will crash, well they didn't do their research properly
this code writes to address 0 and then reads it and just writes a purple character on screen. (check kernel.c)
first install qemu (qemu.org) or your favourite virtualization tool then look at the last line in run.sh
you need nasm and gcc, and just use the script run.sh