I also started to use Keil Software (a beginner). I have tried to run Dhry.uv2 in \keil\c51\example\dhry and it works. However, I tried to sdd some empty line between statements in every module such as Dhry.c or time.c ,I found "step into" didn't match with new module ,it match with old module.I had modify options for each module but it doesn't work. I found it seem to be due to DMO file Also May I know: 1) how do I create a .dmo file 2) what is the usage of it? 3) When should I use it?