Hi Lyndon,

As stated on the Keil website Michael referenced, putchar (used by printf) is implementation dependent.

Unlike a PC environment, the compiler can't know what kind of hardware you have for I/O (LCD? RS232? blinking LEDs?), so you need to write the appropriate function for putchar (and getchar), then maybe recompile the stdio library...unless these came with your board, and in that case you must install them where the compiler can find them.

My compiler's putchar function was simply a return, so it would not do anything (but no error!!).

Dennis