The key assignment of a telephone differs in the way the numbers are arranged when compared to keypads on calculators, cash registers or the numeric keypad on the computer keyboard. The numbers 1, 2 and 3 are located at the top and the 9 is bottom right. In addition, the star and hash keys are at the bottom left and right, on either side of the zero. These two keys can be used to access special features on the phone or telephone network.
Often, in addition to numbers, keys also have three or four letters printed on them. This enables phone lines to be selected not only via numbers, but also through combinations of letters or names. Dialling using letter sequences is very common in North America.