Braille is a system of touch reading and writing used by blind persons. Embossed dots are evenly arranged in quadrangular letter spaces, called cells. A full cell is three dots high and two dots wide. Each cell may contain up to six dots. Only 63 different characters can be formed. Braille is a fixed-width font meaning that every character occupies the same amount of space, regardless of how many dots are in the cell. For braille to be read by a blind person, the dots of each cell must be easily discernible by touch and the height of the dots must be sufficient to be easily distinguished from the background.