I have some problem trying to organize C and header file for my project. I use mbed LPC11U24, and mbed library is updated to latest version. In the top right corner i selected mbed LPC11U24 platform. In my project for example i have 3 files and i want to turn on and off LEDs : 1. main.cpp 2. header_extern.c 3. header_extern.h 1. main.cpp file contains code: {{/media/uploads/elektronika1/main.cpp_file.png}} 2. header_extern.c file contains code: {{/media/uploads/elektronika1/heade.c_file.png}} 3. header_extern.h file contains functions prototype: {{/media/uploads/elektronika1/header.h_files.png}} The main problem is when i use separated c and header files and try to compile it a got lots of errors. If i try to organize all code in one file (main.cpp) everything work perfect. Why this happend? Why i can't call functions which are defined in header_extern.c from file main.cpp? Should i use same older mbed library and which one? this picture show compile errors: {{/media/uploads/elektronika1/compile_errors.png}}