the key word here is "typing". as maverick correctly points out, the added space is used to increase readability when using monospaced typewriter fonts. when using a proportional font, the extra space is not used. this reminds me of the English professor who insisted that papers be typewritten, not printed with proportional fonts, because, he said, the typewritten pages were easier to read. that would have come as a shock to a great many experts on type-setting.