Complex sentence: It was originally used in hand-or typewritten manuscripts to indicate that the text should be typeset in italics, but with the advent of word processing, it has become common in printed text as well.
Split into simpler sentences: It was originally used in hand-written or typewritten manuscripts to indicate that the text should be typeset in a special typeface such as italics. With the advent of word processing, underlining has become common in printed text as well.