Printing "Hello World" to terminal from some board including nrf51822.

I'm a begginer in embedded program. I have a mbed HRM 1017 that is pin-compatible with Nordic PCA10004. . I'd like to make a simple app to print out "Hello World" to terminal.

#include <stdio.h>

 * Print a greeting message on standard output and exit.
 * On embedded platforms this might require semi-hosting or similar.
 * For example, for toolchains derived from GNU Tools for Embedded,
 * to enable semi-hosting, the following was added to the linker:
 * --specs=rdimon.specs -Wl,--start-group -lgcc -lc -lc -lm -lrdimon -Wl,--end-group
 * Adjust it for other toolchains.

		printf("Hello ARM World!" "\n");
  return 0;

image description

This code was created by eclipse on Mac. I built this code to hex file and copied it to mbed through USB.

although I had been watching terminal by "screen /dev/tty.usbmodem1422 9600", Nothing printed.