I've found that I didn't know all the keywords that X++ language has. For example, keywords "window" and "at". And it is probably not so strange, because they are doing the following: position and resize output window. For example, the following code:
static void weirdKeywordsTest()
window 20, 6 at 20, 20;
print "Weird keywords";
Will position output window somewhere in the center and will make it quite small. Furthermore, the maximal window size that can be achieved by using these keywords is 78x22, which is just slightly bigger than default one and only by number of lines. I have no idea why one might need those. Any suggestions?