Dear All, 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 when I type "step into" key , the cursor didn't match with new module ,it match with the posititon in old module.I found it seem to be due to DMO file Because after build only .DMO keep old time. other is update to new time. It is my big trouble ,because I couldn't study next when this bottleneck is still existed . BR.