printf not printing on console

Output is buffered.

stdout is line-buffered by default, which means that '\n' is supposed to flush the buffer. Why is it not happening in your case? I don't know. I need more info about your application/environment.

However, you can control buffering with setvbuf():

setvbuf(stdout, NULL, _IOLBF, 0);

This will force stdout to be line-buffered.

setvbuf(stdout, NULL, _IONBF, 0);

This will force stdout to be unbuffered, so you won't need to use fflush(). Note that it will severely affect application performance if you have lots of prints.

Apparently this is a known bug of Eclipse. This bug is resolved with the resolution of WONT-FIX. I have no idea why though. here is the link: Eclipse C Console Bug.

You could try writing to stderr, rather than stdout.

fprintf(stderr, "Hello, please enter your age\n");

You should also have a look at this relevant thread.

Try setting this before you print:

setvbuf (stdout, NULL, _IONBF, 0);