But is that an O or an 0? Of course, care was taken to display them differently, and the same could have been done with l and 1, as coding fonts commonly do now.
No, the real reason is that upper case was customary for telegrams and then teletypes. Upper case was well established before CRT displays came into play.
No, the real reason is that upper case was customary for telegrams and then teletypes. Upper case was well established before CRT displays came into play.