Hello everyone I am relatively new to the 8051. I am running in to problem creating a simple app with the ATMEL89C55. I created a new project called test and insert 2 files, test.c and STARTUP.A51. It is my understanding that the STARTUP file is required to reset the memory of the microcontroller. In my test.c, all I have is a printf statement. When I create the target I get 2 warnings: ***Warning L1: Unresolved external symbol symbol: ?B_SWITCH0 module: STARTUP.OBJ (?C_STARTUP) etc... When I try to run it under the debug mode, it seems to be stuck in an endless loop on the statements: IF IDATALEN <> 0 MOV R0,#IDATALEN - 1 CLR A IDATALOOP: MOV @R0,A DJNZ R0,IDATALOOP ENDIF Any help would be greatly appreciated. Much thanks in advance. Thomas