If this is your first code on mbed, you should rather go to this code /teams/mbed/code/mbed_blinky/

Here is why: This helloword source code (which by the way is identical to mbed_blinky) is associated with an older version of the mbed library. Consequently, if you have hardware newer than the library, your program may not compile.

This code's current library version is https://developer.mbed.org/users/mbed_official/code/mbed/builds/9296ab0bfc11

You can see this for yourself by inspecting the contents of the mbed.bld file, which points to the associated mbed library. https://developer.mbed.org/users/cputalk/code/HelloWorld/file/1e30337600e4/mbed.bld

/teams/mbed/code/mbed_blinky/ is the exact same code (except for less comments) but that code seems to be managed to always associate with the latest available mbed library version.

If you are the sentimental type who prefer "helloworld" and your compile fails, use the "update library" feature in the online compiler to update to the latest mbed library version.

I will also update this fork every now and then. (Latest update 11/11/2015)

If this was helpful in any way, please notify me by posting a comment below, because so far I could not convince anyone that this is even an issue.