hi, recently i instaled uvision 2.38 on my computer.but when i want to build and compile a project the uvision halts . when i erase the "#include <reg51.h>" command the uvision don't stop but i get the "error C202: 'TH1': undefined identifier" error message" please tell me what is the problem. i must say that i don't have the problem with the previous versions" thanks very much.