7-Segment Display Common Cathode
Seven-segment displays are widely used in digital clocks, electronic meters, basic calculators, and other electronic devices that display numerical information.
Hexadecimal digits can be displayed on seven-segment displays. Today, a combination of uppercase and lowercase letters is commonly used for A–F; this is done to obtain a unique, unambiguous shape for each hexadecimal digit (otherwise, a capital ‘D’ would look identical to a ‘0’ and a capital ‘B’ would look identical to an ‘8’). Also the digit ‘6’ must be displayed with the top bar lit to avoid ambiguity with the letter ‘b’.