A complex number is also a multivalue object. It consists of two parts: real part and imaginary part. The imaginary part carries symbol i which is equal to √-1 . A complete number is written as sum of the real part and the imaginary part as shown below.

When structures are used to keep record of employees, students, and so on, we would need to sort them according to some criterion. For employees, it may be according to alphabetical order, designation, or pay.

Pointers to structures may be declared as we declare pointers to any other data type. Like arrays and functions, the name of structure carries the address of the structure where the values of its various members are stored. Therefore, the pointer may be initialized by the name of structure which is a constant pointer to the structure. Program illustrates the declaration and use of pointer to a structure.

In this method, the declaration starts with typedef followed by key word struct. The data members of the structure are placed between a pair of curly braces after struct. The type name is placed after the closing right brace (}). This is explained in the following example:

The program given below reads the information about a person and prints it on the screen. It uses a structure containing a pointer member name to represent the information about a person. Note that the program uses the dstr_read function.

The C language permits structures to be nested, in which a structure can contain structure members. A structure may be declared inside another structure. Also, a structure may be a data member of another structure. The important thing to note is how to initialize the data members of inner structures and how to access the data members of inner structures. The use of such nested structures facilitates representation and processing of complex data.

Consider the problem of comparison of two valid dates d₁ and d₂. There are three possible outcomes of this comparison: d₁ == d₂ (dates are equal), d₁ > d₂ (date d₁ is greater, i.e., occurs after d₂) and d₁ < d₂(date d₁ is smaller, i.e., occurs before d₂). Let us write a function that accepts two dates as structures dl and d2 of type struct date and returns 0 if the dates are equal, 1 if d₁ is later than d₂ and -1 if date d_l is earlier than d₂.

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.