The following command searches all of the Arduino core code and bootloaders for "hello world." It's not there.
I thought...new duemilanove boards had 'hello world...
@retrolefty (from another thread)
Show the open source code or it didn't happen.
The bootloaders in the Arduino distribution do not put any code in program memory. Nothing in the bootloader itself executes a "Morse Code '1'" program sequence or "hello world" either.
When Arduino boards are set for release from manufacturing, apparently a sketch is loaded into program memory (also: a serial number is placed in EEPROM).
I haven't found any references to indicate what program is put in there. Older "Genuine" Arduino Duemilanove cards apparently had the "Blink" example program put there. I don't have one of the Uno cards, and so haven't been able to observe the Morse Code '1' that was reported by Grumpy_Mike (who, apparently, knows his Morse).
I burned the optiboot loader into ATmega328p CPUs on several of my homebrew cards. Before ever loading a program of any kind, it gives three quick flashes of the LED and the pattern repeats after a second or so. (I didn't time it with a stopwatch, and I don't really care). I also put an optiboot-loaded '328p on my "Genuine" Duemilanove card.
I will mention in passing that the optiboot loader works just fine with the FTDI interface of all of my cards In the Arduino IDE, I select Uno as the card type and it still uses /dev/ttyUSB0 on my Linux systems and the same COM port (COM7 or COM8 or some such thing) as it did before on my Windows XP system. Not so much as a hiccup.
Anyhow, back to the Morse Mystery:
Vendors of cards other than "Genuine" Arduino Uno cards may put something other than the "didahdahdahdah" pattern of the Morse '1'. I mean, if I were doing it, "hello world" might be something I would put there. That was my first example.
I kind of doubt that anyone would put "what a goose I am" (my second example) into their product, but I threw that in there as a possibility just because I felt like it. (It amused me to do so.)
If I were serious about this, I would make the LED blink a copyright notice (in International Morse Code) so that unauthorized copies of the product could be detected by Customs as they sneakily tried to make their way into the mainstream. (But I'm not really serious.)
IBM did something like that in the BIOS of the original PC back in 197-something. Their office suite looked for the IBM copyright notice text in their BIOS ROM and refused to run on a clone. That was typical of IBM, but not very acceptable in the brand new (at the time) culture of Personal Computing. I seem to recall that, putting it mildly, the IBM office suite was not a huge commercial success.