A tablet computer is a mobile computer with a touchscreen display, circuitry and battery in a single unit. Tablets come equipped with sensors, including cameras, a microphone and an accelerometer, and the touchscreen display uses finger or stylus gesturessubstituting for the use of computer mouse and keyboard. They usually feature on-screen, pop-up virtual keyboards for typing. Tablets may include physical buttons for basic features such as speaker volume and power, and ports for network communications and battery charging. Tablets are typically larger than smartphones or personal digital assistants at 7 inches (18 cm) or larger, measured diagonally. Tablets can be classified into several categories according to the presence and physical appearance of keyboards.Slates and booklets do not have a physical keyboard and typically feature text input performed through the use of a virtual keyboard projected on a touchscreen-enabled display. Hybrids and convertibles do have physical keyboards, although these devices typically also make virtual keyboards available.