I have a project linked correctly with the BL51 linker. If I change this linker by the Extended Linker (LX51)it returns the following error: - ERROR L121: IMPROPER FIXUP MODULE: C:\KEIL6.23\C51\LIB\C51C.LIB (PRINTF) SEGMENT: ?PR?PRINTF?PRINTF OFFSET: 000068H And the same for RAND fucntion. I guess I should recompile libraries in C:\KEIL6.23\C51\LIB\ in order to use the LX51 linker. Can anybody help me? Thanks Aitor