I have lost all my pictures out of i photos, i did not delete them, i just switched application and then when i went to i photos they had all gone ? does anyone know where to find them or how do i do a system restore on a imac ? i am new to macs, i know how to do pc but not sure on this ? also i keep having a terminal box popping up when i start that says darwin inside the box ? please help, i have lost all pictures of my baby boy .

Thanks alot