Thus far we have studied as to how the data of heterogeneous nature can be grouped together and be referenced as a single unit of structure. Now we come to the next step in our real world problem. Let’s consider the example of students and their marks. In this case, to avoid declaring various data variables, we grouped together all the data concerning the student’s marks as one unit and call it student. The problem that arises now is that the data related to students is not going to be of a single student only. We will be required to store data for a number of students. To solve this situation one way is to declare a structure and then create sufficient number of variables of that structure type. But it gets very cumbersome to manage such a large number of data variables, so a better option is to declare an array.
So, revising the array for a few moments we would refresh the fact that an array is simply a collection of homogeneous data types. Hence, if we make a declaration as:
int temp[20];
It simply means that temp is an array of twenty elements where each element is of type integer, indicating homogenous data type. Now in the same manner, to extend the concept a bit further to the structure variables, we would say,
struct student stud[20] ;
It means that stud is an array of twenty elements where each element is of the type struct student (which is a user-defined data type we had defined earlier). The various members of the stud array can be accessed in the similar manner as that of any other ordinary array.
For example,
struct student stud[20], we can access the roll_no of this array as
stud[0].roll_no;
stud[1].roll_no;
stud[2].roll_no;
stud[3].roll_no;
…
…
…
stud[19].roll_no;
Please remember the fact that for an array of twenty elements the subscripts of the array will be ranging from 0 to 19 (a total of twenty elements). So let us now start by seeing how we will write a simple program using array of structures.
Write a program to read and display data for 20 students.
/*Program to read and print the data for 20 students*/
#include <stdio.h>
struct student { int roll_no;
char name[20];
char course[20];
int marks_obtained ;
};
main( )
{
struct student stud [20];
int i;
printf (“Enter the student data one by one\n”);
for(i=0; i<=19; i++)
{
printf (“Enter the roll number of %d student”,i+1);
scanf (“%d”,&stud[i].roll_no);
printf (“Enter the name of %d student”,i+1);
scanf (“%s”,stud[i].name);
printf (“Enter the course of %d student”,i+1);
scanf (“%d”,stud[i].course);
printf (“Enter the marks obtained of %d student”,i+1);
scanf (“%d”,&stud[i].marks_obtained);
}
printf (“the data entered is as follows\n”);
for (i=0;i<=19;i++)
{
printf (“The roll number of %d student is %d\n”,i+1,stud[i].roll_no);
printf (“The name of %d student is %s\n”,i+1,stud[i].name);
printf (“The course of %d student is %s\n”,i+1,stud[i].course);
printf (“The marks of %d student is %d\n”,i+1,stud[i].marks_obtained);
}
}
The above program explains to us clearly that the array of structure behaves as any other normal array of any data type. Just by making use of the subscript we can access all the elements of the structure individually.
Extending the above concept where we can have arrays as the members of the structure. For example, let’s see the above example where we have taken a structure for the student record. Hence in this case it is a real world requirement that each student will be having marks of more than one subject. Hence one way to declare the structure, if we consider that each student has 3 subjects, will be as follows:
struct student {
int roll_no;
char name [20];
char course [20];
int subject1 ;
int subject2;
int subject3;
};
The above described method is rather a bit cumbersome, so to make it more efficient we can have an array inside the structure, that is, we have an array as the member of the structure.
struct student
{
int roll_no;
char name [20];
char course [20];
int subject [3] ;
};
Hence to access the various elements of this array we can the program logic as follows:
/*Program to read and print data related to five students having marks of three subjects each using the concept of arrays */
#include<stdio.h>
struct student {
int roll_no;
char name [20];
char course [20];
int subject [3] ;
};
main( )
{
struct student stud[5];
int i,j;
printf (“Enter the data for all the students:\n”);
for (i=0;i<=4;i++)
{
printf (“Enter the roll number of %d student”,i+1);
scanf (“%d”,&stud[i].roll_no);
printf(“Enter the name of %d student”,i+1);
scanf (“%s”,stud[i].name);
printf (“Enter the course of %d student”,i+1);
scanf (“%s”,stud[i].course);
for (j=0;j<=2;j++)
{
printf (“Enter the marks of the %d subject of the student %d:\n”,j+1,i+1);
scanf (“%d”,&stud[i].subject[j]);
}
}
printf (“The data you have entered is as follows:\n”);
for (i=0;i<=4;i++)
{
printf (“The %d th student's roll number is %d\n”,i+1,stud[i].roll_no);
printf (“The %d the student's name is %s\n”,i+1,stud[i].name);
printf (“The %d the student's course is %s\n”,i+1,stud[i].course);
for (j=0;j<=2;j++)
{
printf (“The %d the student's marks of %d I subject are %d\n”,i+1, j+1, stud[i].subject[j]);
}
}
printf (“End of the program\n”);
}
Hence as described in the example above, the array as well as the arrays of structures can be used with efficiency to resolve the major hurdles faced in the real world programming environment.