The $CITY. format converts each of the codes BR1, BR2, and so on, to the name of the corresponding city. The keyword OTHER formats values in the data set that do not match any values on the left side of the equals sign as INCORRECT CODE. 
      value  $city 'BR1'='Birmingham UK'
                   'BR2'='Plymouth UK'
                   'BR3'='York UK'
                   'US1'='Denver USA'
                   'US2'='Miami USA'
                   other='INCORRECT CODE';
   run;