data that consists of more than just textual information - alphanumeric text can be represented using a limited range of ASCII codes from 32 to 127 with some of the numbers below 32 used as control codes such as 10 for linefeed and 12 for formfeed/clear screen - binary data, by contrast, uses all the codes 0 to 255 and, if it were transmitted as if it were a text file, the control codes could have all sorts of undesired effects - other techniques therefore have to be used for its transmission, e.g. uuencoding