Structure In C Language

 Introduction

• Structure can be defined as,"A finite collection of heterogenous elements".
• A Keyword "Struct" is used to declare  a structure.

Syntax-:

                     struct structure name

                            { datatype member name 1;

                               datatype member name 2;

                                 -

                                 -

                                 -

                               datatype member name n;

                             };

Example-:

                       struct Emp

                            { int id;

                               char name[10];

                               float salary;

                             };

• The structure declaration, however does not allocate any memory or consume storage space.Memory allocated for the structure,when we declare a variable of the structure.

Example-:

                     struct Emp

                            {  int id;

                               char name[10];

                               float salary;

                             };

                            struct Emp e1;

• After the compilation of above code,the memory is allocated for the structure variable e1.

sizeof(e1)=4+10+4 =>18 bytes

Initialization Of Structure Variable

• A Structure can be initialize in the same way as other datatype are initialize.Initializing a structure means assigning some constant to member of the structure.
• A Structure can be initialize by providing legal values,according to the structure member to structure variable in the following manner.

Example-:

                    struct Emp

                            { int id;

                               char name[10];

                               float salary;

                             };

                   struct emp e1={0001,"Sudarshan",20000.78};

Accessing Structure Element

• Individual member of a structure variable are referenced by using dot (.) notation in the following manner.

Syntax-:

                      structure variable name.member name;

Example-:

                           e1.id;

                           e1.name;

                           e1.salary;

Initialization Of Structure Variable At Runtime

• A structure variable can also be initialize at runtime in following manner-:

Program-:

struct Emp

{ int id;

   char name[15];

   float per;

};

struct emp e1={0001,"Sudarshan",20000.78},e2;

printf("Enter the id,name and salary-:");

scanf(" %d %s %f ",&e2.id,&e2.name,&e2.salary);

printf("\n Structure Variable Have The Following Value:-\n");

printf("ID=%d,NAME=%s,SALARY=%f",e1.id,e1.name,e1.salary\n);

printf("ID=%d,NAME=%s,SALARY=%f",e2.id,e2.name,e2.salary);

getch();

}

Output-:

Enter the id,name and salary-:0002

Arun

25000.782

 Structure Variable Have The Following Value:-

ID=0001 NAME=Sudarshan SALARY=20000.78

ID=0002 NAME=Arun SALARY=25000.78

Finding Structure Size

• The sizeof operator is a uniary operator used to calculate the sizeof data type,this operator is applied at all the data type.
• The operator return the sizeof the variable or expression in bytes, To calculate the size of structure using the sizeof operator the following syntax is used.

Syntax-:

                Variable=sizeof(structure variable name);

Program-:

struct Emp

{ int id;

   char name[15];

   float per;

};

struct emp e1={0001,"Sudarshan",20000.78};

printf("\n Size of Emp is %d".,sizeof(e1));

getch();

} 

Output-:

Size of Emp is 18.