Structures in C language are basically user-defined data types that enables the user to create a data type that can group elements of different data types into it.
Thus, it contains different data types to be represented by a single Structure name.
Creating Structures in C
C language uses the struct keyword to create a structure.
Syntax:
struct Structure_Name
{
Datatype data_member1;
Datatype data_member2;
.
.
Datatype data_memberN;
};
As mentioned above, C language uses the struct keyword to build a structure. Inside the curly brackets, the user can define the data members necessary to serve the purpose of the particular program. These data members are the basic C language variables of different data types such as int, float, double, char, etc.
It is mandatory to add a semi-colon (;) after the closing curly bracket of a particular structure.
Example:
struct Student_info
{
char name[100];
char address[100];
char division[50];
int roll_num;
};
In the above code snippet, we have created a structure as Student_info to serve the purpose of Student Information. Within the structure, we have declared data members: name, address, division, and roll_num with their particular data type.
Declaration of Structure Variables
Structure Variables enable the user to access the data-members declared inside the structure.
Either of the following ways can be used to declare Structure Variables in C:
- Declaration of Structure variables after the Structure definition
- Declaration of Structure variables along with the Structure definition
1. Declaration of Structure variables after the Structure definition
Syntax:
struct Structure_Name
{
Datatype data_member1;
Datatype data_member2;
.
.
Datatype data_memberN;
};
struct Structure_Name Variable1, Variable2,.., VariableN;
Example:
struct Student_info
{
char name[100];
char address[100];
char division[50];
int roll_num;
};
struct Student_info S1, S2;
In the above snippet of code, we have created Structure Variables S1 and S2 for the Structure Student_info after the declaration of the structure.
2. Declaration of Structure variables along with the Structure definition
Syntax:
struct Structure_Name
{
Datatype data_member1;
Datatype data_member2;
.
.
Datatype data_memberN;
} Structure_variable1, Structure_variable2;
Example:
struct Student_info
{
char name[100];
char address[100];
char division[50];
int roll_num;
}S1, S2;
In the above piece of code, we have created the Structure Variables S1 and S2 along with the declaration of the structure Student_info.
Initializing Structure Data Members
The C Structure data members cannot be initialized while declaring them. They need to be separately assigned values after the declaration of data members of the structure.
Example: Declaring Structure Data members while declaring them gives an error
struct Student_info
{
char *name = "Safa"; // This statement gives compilation error
};
As mentioned above, the Structure data members need to be initialized separately after the declaration.
Syntax:
Structure_Name.Structure_data_member_name = Value
Accessing data members in a Structure
C uses the period or member access operator (.) to access the data members of the structure.
Syntax:
Structure_variable_name.Structure_data_member_name
Example:
#include <stdio.h>
struct Student_info
{
char *name;
char *address;
char *division;
int roll_num;
};
int main()
{
struct Student_info S1;
S1.name = "Safa Mulani";
S1.address = "Pune";
S1.division = "A";
S1.roll_num = 24105;
printf("The Student Information is as follows:n");
printf("nName: %s", S1.name);
printf("nAddress: %s", S1.address);
printf("nDivision: %s", S1.division);
printf("nRoll Number: %d", S1.roll_num);
return 0;
}
Here, we have created variable S1 of type struct. Further, we have accessed the structure variables: name, address, division and roll_num using S1.
Output:
The Student Information is as follows: Name: Safa Mulani Address: Pune Division: A Roll Number: 24105
Array of Structure
C allows the users to use an array to represent the data elements of the Structure.
Syntax:
struct Structure_Name array_name[size];
In the below snippet of code, we have created an array ‘S’ of structure Student_info with size = 3.
Example:
#include<stdio.h>
struct Student_info
{
char name[100];
char division[50];
int roll_num;
};
void main()
{
struct Student_info S[3];
for(int i = 0; i < 3; i++)
{
printf("nEnter Student Details:n");
printf("nName:t");
scanf("%s", S[i].name);
printf("nDivision:t");
scanf("%s", S[i].division);
printf("nRoll Number:t");
scanf("%d", &S[i].roll_num);
}
printf("nStudent Information:n");
for(int i = 0; i < 3; i++)
{
printf("nName: %s", S[i].name);
printf("nRoll Number: %d", S[i].roll_num);
printf("nDivision: %s", S[i].division);
}
}
Output:
Enter Student Details: Name: Safa Division: A Roll Number: 23105 Enter Student Details: Name: Aman Division: B Roll Number:21042 Enter Student Details: Name: Divya Division: D Roll Number: 2134 Student Information: Name: Safa Roll Number: 23105 Division: A Name: Aman Roll Number: 21042 Division: B Name: Divya Roll Number: 2134 Division: D
Structure as Function Parameters
C enables programmers to pass a Structure as an argument to a function in a similar fashion of passing variables/arrays as arguments to functions.
Example:
#include <stdio.h>
struct Evaluation
{
char name[50];
int score;
};
void display_details(struct Evaluation e1);
int main()
{
struct Evaluation e;
printf("Name: ");
scanf("%[^n]%*c", e.name);
printf("Score: ");
scanf("%d", &e.score);
display_details(e); // passing structure as an argument
return 0;
}
void display_details(struct Evaluation e1)
{
printf("nEvaluation details.....n");
printf("Name: %s", e1.name);
printf("nScore: %d", e1.score);
}
Output:
Name: Safa Score: 56 Evaluation details..... Name: Safa Score: 56
Nested Structures
Nested Structures in C basically defining one structure into another structure i.e. it permits one structure to have another structure as a variable.
Example:
struct Student_info
{
char *name;
char *Branch_name;
struct Evaluation
{ char *division;
int hsc_score;
int ssc_score;
int roll_num;
}eval;
}student;
In the above snippet, We have created a structure Student_info wherein we have represented another structure Evaluation as a member of it.
You can access the nested structs using struct1_var.struct2_var.struct2_innervar
For example, in the above example, we used student as struct 1 variable and eval for the nested struct. We can access the inner variables as student.eval.ssc_score;
Pointers in Structure
C allows us to have a pointer to a structure. The arrow (->) operator enables the user to access the data members of the structure having a pointer to it.
Syntax:
struct Structure_Name
{
Datatype data_member1;
Datatype data_member2;
.
.
Datatype data_memberN;
};
int main()
{
struct Structure_Name *pointer_name;
}
Example:
#include<stdio.h>
struct Student_info
{
char *name;
int roll_num;
};
int main()
{
struct Student_info *St, S;
St = &S;
printf("nEnter Student Details:n");
printf("nName:t");
scanf("%s", St->name);
printf("nRoll Number:t");
scanf("%d", &St->roll_num);
printf("nStudent Information:n");
printf("nName: %s", St->name);
printf("nRoll Number: %d", St->roll_num);
return 0;
}
Output:
Enter Student Details: Name: Safa Roll Number: 1234 Student Information: Name: Safa Roll Number: 1234
Conclusion
Thus, in this article, we have understood the concept of Structures in C language.