To control LEDs with DE0_Nano

There are some mistakes in your code, I assume they come from a copy/paste error. The include line should be

#include <system.h>

and you didn't close the string in the printf line. You should also end the line with a \n to be sure it is written to the UART.

Are you sure you upload the correct .sof image to the FPGA before you upload and run the software?

And here is a tip: when you show some code, enclose it between [code] and [/code] tags, and you won't loose formatting and indentation.