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Structures

What is a structure in C

Example: storing employee information

  • Structures are user defined data type.
  • Supporse we want to store information of 10,000 employees working at Abc Pvt. Ltd.
    • Name
    • Address
    • Email
    • Employee id
  • Clearly we need some user defined data type which contains only this information.

Defining a structure

                        

                            struct [structure_name]
                            {
                                //data_type var 1
                                //data_type var 2
                                //data_type var 3 ..
                            }
                            [structure_variables];

Defining a structure to store students ID, marks and favourite character

                            

                                struct Student
                                {
                                    int id;
                                    int marks;
                                    char fav_char;
                                } s1,s2,s3;
                                // new datatype whose name is student and this is achieved by structure;

Declaring a structure;

We can either declare a structure along with structure definition or separately.

                        

                        //Declaring a structure along with structure definition
                        #include <stdio.h>
                        struct Employee
                        {
                            int id;
                            char name[53];
                            float marks;
                         };

                        struct Employee e1,e2;

                         int main()
                        {
                            return 0;
                        }
                    
                    
                        

                        //Declaring a structure separate from structure definition
                        #include <stdio.h>
                        struct Employee
                        {
                            int id;
                            char name[53];
                            float marks;
                        } e1,e2;
                        
                         int main()
                        {
                            struct Employee tt;
                            //this creates one more variables
                            return 0;
                         }

Initializing a structure;

We can either initialize a structure along with structure definition or separately.

                        

                        //Initializing a structure along with structure definition
                        #include <stdio.h>
                        struct Employee
                        {
                            int id;
                            float marks;
                         };

                        struct Employee e1,e2;

                        int main()
                        {
                            struct Employee e1;
                            e1.id = 12;
                            e1.marks = 34.12;
                            return 0;
                         }
                        
                        
                        
                        //Initializing a structure separate from structure definition
                        #include <stdio.h>
                        struct Employee
                        {
                            int id;
                            float marks;
                         };
                        
                         int main()
                        {
                            struct Employee e1 = {12, 34.12};
                            return 0;
                         }

Accessing structure members

  • Array elements are accessed using the subscrpt variable (arr[0],arr[1]...).
  • In a similar fashion, structure members are accessed using dot[.] operator
  • [.] is called as "structure member operator"
  • To access the member of the structure, we use this operator in between "Structure name" & "member name"
                        

                                #include <stdio.h>
                                #include <string.h>
                                struct Student
                                {
                                    int id;
                                    int marks;
                                    char fav_char;
                                    char name[34];
                                };
                                int main()
                                {
                                    struct Student harry, ravi;
                                    harry.id = 1;
                                    harry.marks = 466;
                                    strcpy(harry.name, "Harry Coder");
                                    harry.fav_char = 'p';
                                    ravi.id = 2;
                                    ravi.marks = 466;
                                    ravi.fav_char = 'p';
                                    strcpy(ravi.name, "Ravi Kumar");
                                    struct Student subham = {3, 466, 'p', "Subham Kumar"};
                                    // printf("Harry got %d marks", harry.marks);
                                    // quick quiz
                                    // print all information of a given student
                                    printf("Harry's full name is %s, ID is %d, marks = %d and favourite character = %c \n", harry.name, harry.id, harry.marks, harry.fav_char);
                                    printf("Ravi's full name is %s, ID is %d, marks = %d and favourite character = %c\n", ravi.name,
                                           ravi.id, ravi.marks, ravi.fav_char);
                                    printf("Subham's full name is %s, ID is %d, marks = %d and favourite character = %c\n", subham.name, subham.id, subham.marks, subham.fav_char);
                                    return 0;
                                }