Pragmatically, when you have a chunk of recognizable text in the right column, it strongly indicates that you should not attempt to interpret the corresponding hex bytes as binary data. And if you don't have text, then it very likely is binary data. In old COBOL programs much of the data is stored as strings (albeit in EBCDIC rather than ASCII), so what this usually tells you is whether you're looking at data or program, which is a very important distinction when you're trying to decipher a core dump. Even if your binary machine code happens to fall in the range of characters, it'll just be gibberish on the right, which tells you at a glance that it's probably not text.