And I hope all this criticism isn't too down-heartening... at least from my part (though I strongly believe it is the same for others too) it's intended as friendly and genuine constructive criticism.
Not at all. I always welcome constructive criticism; any opportunity to improve myself, I much appreciate. For my part, any criticism I offer, including the linked article itself, I likewise intend to be constructive.
BTW, I got the string "Hello Worldp" from the first program, using the same compiler configuration. I had to use std=c99 to get it to compile (the variable in the for loop).