Function            isstate - is string a state abbreviation

  Syntax              boolean isstate(char *state);

  Prototype in        statehk.h

  Remarks             isstate() looks up the state abbreviation given in
                      States[]. The search is case independent

  Return value        returns TRUE if found, otherwise FALSE.

  Note                in addition to the 50 states, the following are
                      also recognized:

                           CZ   - Canal Zone
                           DC   - District of Columbia
                           GU   - Guam
                           PR   - Puerto Rico
                           VI   - Virgin Islands

  See also            statehk.h
                      iszip(), stateindex()

  Example             #include <statehk.h>

                      {
                           printf("AL is ");
                           if (!isstate("AL"))
                                printf("NOT ");
                           printf("a valid state abbreviation\n");
                      }

  Program output      AL is a valid state abbreviation