Example

Declare the structure /STUDENT/ to contain either NAME, CLASS, and MAJOR, or NAME, CLASS, CREDITS, and GRAD_DATE:

       STRUCTURE /STUDENT/ 
       CHARACTER*32  NAME 
       INTEGER*2  CLASS 
       UNION 
              MAP 
                     CHARACTER*16 MAJOR 
              END MAP 
              MAP 
                     INTEGER*2  CREDITS 
                     CHARACTER*8  GRAD_DATE 
              END MAP 
       END UNION 
       END STRUCTURE 
       RECORD /STUDENT/ PERSON 

In the above example, the variable PERSON has the structure /STUDENT/, so:

• PERSON.MAJOR references a field from the first map; PERSON.CREDITS references a field from the second map.

• If the variables of the second map field are initialized, and then the program references the variable PERSON.MAJOR, the first map becomes active, and the variables of the second map become undefined.