These common anode/cathode are internally shorted so we need to connect only one COM pin. There are 10 pins, in which 8 pins are used to refer a,b,c,d,e,f,g and h/dp, the two middle pins are common anode/cathode of all he LEDs. We can refer each segment 'a,b,c,d,e,f,g' and for dot character we will use 'h'.
As shown in the above image of a 7-segment display, it consists of 8 LEDs, each LED used to illuminate one segment of unit and the 8 thLED used to illuminate DOT in 7 segment display. We can refer each segment as a LINE, as we can see there are 7 lines in the unit, which are used to display a number/character. It is also able to form some alphabets like A, B, C, H, F, E, etc.ħ segment displays are among the simplest display units to display the numbers and characters.
As its name indicates, it is made of seven different illuminating segments which are arranged in such a way that it can form the numbers from 0-9 by displaying different combinations of segments. They are most commonly used in electronic devices like digital clocks, timers and calculators to display numeric information. A seven-segment display (SSD) is a widely used electronic display device for displaying decimal numbers from 0 to 9.
