When digital panel meters first appeared on the market the convention of using a full-scale display range of "000" to "1999" for 3½ digit meters and "0000" to "19999" for 4½ digit meters became an industry standard. And, for reasons still unknown to this writer, the leading left-most "1" (also referred to as the most significant digit, or MSD) became known as the infamous "half-digit". This half-digit represents the one-thousands digit on a 3½ digit meter and the ten-thousands digit on a 4½ digit meter.
