You can toggle an alphabetic character between upper and lower case by simply inverting bit five. Note that you cannot convert a string of numeric characters to their equivalent binary representation by simply stripping the H.O. nibble from each digit in the string. 010203h, not the correct value which is 7Bh. Most printers support IBM's character set as well. Worse still, different machines often use these control codes in different ways.
End of line is a particularly troublesome example.
Apple Macintosh, Apple II, and many other systems mark the end of line by a single CR character. UNIX systems mark the end of a line with a single LF character. Needless to say, attempting to exchange simple text files between such systems can be an experience in frustration. Fortunately, such conversions are rather simple.