I am using robot C v 3.0, and I am trying to get input and print it on the console, printf(); doesn't work, any ideas?

nxtDisplayTextLine(2, "%2.2f", variable);
try that.

Depends on where you want to print the output.
nxtDisplayTextLine() will print the output to the NXT LCD screen. If you want to print the output to the debug console then use either writeDebugStream or writeDebugStreamLine. The syntax is exactly like printf.