Hello, i have created a simple "hello world" application with one button. click on the button and "hello world!" appears in the center of the window. it works fine. Now, i include 2 simple plain c file in this project: info.h info.c I would like to call the info() function from the info.c and return/output its result in the window like the message "hello world!" when i push the button. My intention is to use plain c as core and obj-c as GUI. How can i do this without to change/rewrite c-code inside info.c to use obj-c GUI? here is the hello world project with obj-c and c-files: http://www.mediafire.com/download.php?znhwmwnyzzz Would you please download it and make the necessary changes for me so that i can use it as a example to better understand how it works. Thank you!