Some displays can show only digits or alphanumeric characters. They are called segment displays, because they are composed of several segments that switch on and off to give appearance of desired glyph. The segments are usually single LEDs or liquid crystals. They are mostly used in digital watches and pocket calculators. There are several types:

• Seven-segment display (most common, digits only)
• Fourteen-segment display
• Sixteen-segment display
• HD44780 LCD controller a widely accepted protocol for LCDs.