Imag­ine dial­ing a phone num­ber by hav­ing to look up each dig­it one at a time in the phone book. Nor­mal­ly, you look up the num­ber and remem­ber all sev­en dig­its long enough to get it dialed. Even with one dig­it at a time, you would have to remem­ber each dig­it long enough…