In C, structures can be nested. A structure can be defined within in another structure. The members of the inner structure can be accessed using the variable of the outer structure as shown below:
outer–struct–variable.inner–struct–variable.membername
An example for a nested structure is shown below:
1 2 3 4 5 6 7 8 9 10 11 12 13 | struct student { struct { char fname[20]; char mname[20]; char lname[20]; } name; char grade; }; struct student s1; strcpy(s1.name.fname, "satish"); |
In the above example, student is the outer structure and the inner structure name consists of three members: fname, mname and lname.
Structures and Functions
We know that the functions are the basic building blocks of a C program. So, it is natural for C language to support passing structures as parameters in functions. We pass a copy of the entire structure to the called function. Since the function is working on a copy of the structure, any changes to structure members within the function are not reflected in the original structure. The syntax for passing the structure variable as a parameter is shown below:
1 2 3 4 5 6 7 8 9 | return–type function–name(struct structname var) { —— —— —— return expression; } |
We can access and assign values to the members of a structure in a number of ways. As mentioned earlier, the members themselves are not variables. They should be linked to the structure variables in order to make them meaningful members. The link between a member and a variable is established using the member operator ‘ . ‘ which is also known as dot operator or period operator. The syntax for accessing a structure member is as shown below:
structure–varaible.membername
Examples of accessing the members of the student structure are shown below:
1 2 3 4 | student1.name student1.age |
Structure Initialization
Like any other data type, a structure variable can be initialized at compile time. An example of compile time initialization of the student structure is shown below:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 | struct student { char name[20]; char rollno[15]; int age; char grade; }; struct student student1 = { "teja", "10A1", 26, 'A' }; struct student student2 = { "raju", "10A2", 24, 'B' }; |
In the above example: teja, 10A1, 26 and A are assigned to student1’s name, rollno, age and grade. Whereas raju, 10A2, 24, B are assigned to student2’s name, rollno, age and grade.
Note: Partial initialization of a structure variable is supported. For example we can assign values to name and rollno and leave out age and grade. In case of partial initialization, the default values for int type is zero. For float and double it is 0.0. For characters and strings it is ‘\0’.
An example for dynamic initialization is shown below:
1 2 3 4 5 6 | gets(student1.name); gets(student1.rollno); scanf("%d", & student1.age); scanf("%c", & grade); |
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