structures and unions learning objective today' modern applications need complex data structures to support them structure is collection of related data items of different data types it extends the concept of arrays by storing related information of heterogeneous data types together under single name it is useful for applications that need lot more features than those provided by the primitive data types union is also collection of variables of different data typesexcept that in case of unionsyou can only store information in one field at any one time in this we will learn how structures and unions are declareddefinedand accessed using the language introduction structure is in many ways similar to record it stores related information about an entity structure is basically user-defined data type that can store related information (even of different data typestogether the major difference between structure and an array is that an array can store only information of same data type structure is therefore collection of variables under single name the variables within structure are of different data types and each has name that is used to select it from the structure structure declaration structure is declared using the keyword struct followed by the structure name all the variables of the structure are declared within the structure structure type is generally declared by using the following syntaxstruct struct-name data_type var-name