I create a new project from Keil C51 IDE and then add my source code into it. When invoked linker links my project, the error occurs as follows: *****FTAA ERROR L210:I/O ERROR ON INPUT FILE EXCEPTION 0021H: PATH OR FILE NOT FOUND FILE CCAPI.OBJ I searched my folder for the file ccapi.obj and really did not found it. I know the file ccapi.obj can not be generated by compiler. But I do pnot set the directive SRC in my code or project setting. Any one can give me a hand ? What does caused the result? Thanks any help in advance!