This site contains a free C compiler dedicated to all micro controller fans.
This compiler is intended to work with AVR micro controllers from ATMEL.
The principle is to create assembler code from C code using micro-IDE studio and create assembler hex file to be loaded to the AVR chip using the free avr studio from ATMEL.(it will be used as debugger).
Its very simple to work with the studio, after writing your code in C language all you have to do is click one button and it will automatically compile and build and load to the micrcontroller.
To make things more easier for debugging LCD16x2 is connected in 4 bit mode to port E and its possible to print text or variable continent using simple commands.