Structures

Arrays can be used to handle several elements of the same type together. However, sometimes it would be useful to handle several data elements of different types as a unit. In C++ structures are used for this purposes.

Structures (like arrays) are called structured data types, i.e. they have a structure defined by the programmer. A structure is declared:

struct type_name
{
    data_type member_name1;
    ...
    data_type member_nameN;
};

This defines a new type called type_name which can be used as any other type in C++. Note the semicolon (;) at the end. It is a mandatory while declaring a structure.

The individual members in the structure act like any other variable with the type data_type. The members can be accessed using . (dot) operator:

struct Student
{
    string name;
    int student_number;
};
...
Student st; // Declare a new variable of type Student
...
st.name = "Harry Potter";
cin >> st.student_number;

The members of a structure can also be initialized with literals of the same type as the members:

Student harry=
{
    "Harry Potter", 12345
};

The members are initialized in the order they appeared at the declaration. A new value can be assigned to a structure with =, but comparison ( == and != ) is not possible.

The members can be of any type, including arrays:

struct Grade
{
    string name,
    int problem_points[4];
};
...
Grade grade1;
...
grade1.problem_points[2] = 5;

On the other hand, the elements of any array can be of any type, too, including structures:

Student students[200];
...
students[0].name = "Ron Weasley";
cin >> students[54].student_number;

A struct is an aggregate of elements of (nearly) arbitrary types. Structures allow the programmer to define a new data type and group related components together. When structure is passed as a parameter of a function, by default it is passed by value but it can be passed by reference as well.

Reference: fredosaurus, wikipedia, msdn

Previous post

Next post