Structures and Unions, Giving values to members, Initializing structure, Functions and structures, Passing structure to elements to functions, Passing entire function to functions, Arrays of structure, Structure within a structure and Union.

A structure is a user-defined data type containing a collection of logically related data which may be of different types such as int, double, char, and so on. All of them are encapsulated (packed) in a single unit with a single name. The classes of C++ are in fact generalization of C-structures. A class in C++ with only public members is similar to a C-structure. All members of a structure in C are by default public. However, in a class declaration in C++, if there is no access specifier, the members are private by default. We know that arrays can be used to represent a group of data items that belong to the same type, such as int or float. This restriction is not there in structures.

A program to determine the number of words and average word length is given in Program. It uses the strtok function to separate the words in a given string. The program given below uses the same technique to separate the words in a given string and determine and print the frequency of these words.

Since structures are multivalue, multitype data objects, they can be considered to form a useful tool in manipulation of quantities such as vectors, complex variables, etc. For this we define functions of the type struct, i.e., the return value of the function is a structure. The function may have arguments of type struct besides other arguments. Let us define a structure with three components of vector as its data members as shown below.

Let us use structure complex to represent a complex number and write a simple program containing only the main function. Thus, we can define structure complex either in the main function or before it as a global definition.