What are structures and unions?

A structure contains an ordered group of data objects . Unlike the elements of an array, the data objects within a structure can have varied data types. Each data object in a structure is a member or field. A union is an object similar to a structure except that all of its members start at the same location in memory.

A struct in the C programming language (and many derivatives) is a composite data type (or record) declaration that defines a physically grouped list of variables under one name in a block of memory , allowing the different variables to be accessed via a single pointer or by the struct declared name which returns the …

C unions allow data members which are mutually exclusive to share the same memory . This is quite important when memory is valuable, such as in embedded systems. Unions are mostly used in embedded programming where direct access to the memory is needed.