C Structure and Union in C

PAPER: INTRODUCTION PROGRAMMING LANGUAGE USING C
PAPER ID: 20105
PAPER CODE: BCA 105
DR. VARUN TIWARI
(ASSOCIATE PROFESSOR)
(DEPARTMENT OF COMPUTER SCIENCE)
BOSCO TECHNICAL TRAINING SOCIETY,
DON BOSCO TECHNICAL SCHOOL, OKHLA ROAD , NEW DELHI

OBJECTIVES
IN THIS CHAPTER YOU WILL LEARN:
1. TO UNDERSTAND ABOUT STRUCTURE IN C.
2. TO LEARN ABOUT HOW TO DECLARE STRUCTURE IN C.
3. TO LEARN ABOUT HOW TO STORE STRUCTURE IN MEMORY.
4. TO UNDERSTAND COPY OF STRUCTURE ELEMENTS IN C.
5. TO UNDERSTAND ABOUT NESTED STRUCTURE IN C.
6. TO LEARN ABOUT HOW TO USE ARRAY OF STRUCTURE IN C.
7. TO LEARN ABOUT UNION IN C.

STRUCTURE: IT IS REQUIRED TO STORE GROUP OF ALL INFORMATION INTO ONE VARIABLE.
PROGRAMMER CAN USE AN ARRAY TO STORE A GROUP OF DATA ITEM THAT BELONG TO THE SAME
TYPE. BUT IF IT IS REQUIRED TO REPRESENT A COLLECTION OF DATA ITEMS OF DIFFERENT TYPES USING
A SINGLE NAME THEN BE CAN’T WE AN ARRAY. C LANGUAGE PROVIDE A METHOD OF GROUPING ALL
OF THE INFORMATION IN TO ONE VARIABLE IS CALLED A STRUCTURE. A STRUCTURE IS SIMILAR TO A
RECORD. A RECORD CREATED AS A GROUP OF DATA WHICH NEED TO BE PROCESS AS A GROUP FOR
EXAMPLE: FOR ONE STUDENT PROGRAMMER MAY NEED TO BE STORE DATA SUCH AS ROLLNO , NAME
, SUBJECT ,MARKS, TOTAL AND PERCENTAGE. SUPPOSE YOU WANT TO STORE DATA ABOUT A BOOK.
YOU MIGHT WANT TO STORE ITS NAME (STRING),PRICE (FLOAT), NOOFPAGE(INT). IF DATA ABOUT 3
SUCH BOOKS TO BE STORED, THEN WE CAN FOLLOW TWO APPROACH:
1. CONSTRUCT INDIVIDUAL ARRAYS, ONE FOR STORING NAME , ANOTHER FOR STORING PRICE AND
STILL ANOTHER FOR STORING PAGES.
2. USE A STRUCTURE.

EXAMPLE OF FIRST APPROACH:
#include<conio.h>
#include<stdio.h>
void main() {
char name[3]; float price[3];
int page[3],i;
printf("n enter name, price and page of 3 books");
for(i=0;i<=2;i++) {
scanf("%s%f%d",&name[i],&price[i],&page[i]); }
printf("n output value is -:");
for(i=0;i<=2;i++) {
printf("n output is -: %c %f %d",name[i],price[i],page[i]); }
getch(); }

EXAMPLE OF SECOND APPROACH:
void main() {
struct book{
char name; float price;
int page; };struct book b1,b2,b3;
clrscr();
printf("n enter name, price and page of 3 books");
scanf("n %c %f %d",&b1.name,&b1.price,&b1.page);
printf("n output is -:");
printf("n output is -:%c %f %d",b1.name,b1.price,b1.page);
printf("n output is-: %c %f %d",b2.name,b2.price,b2.page);
printf("n output is-: %c %f %d",b3.name,b3.price,b3.page);
getch(); }

STRUCTURE DECLARATION: THIS PROGRAM DEMONSTRATE TWO FUNDAMENTAL ASPECTS OF STRUCTURE.
A). DECLARATION OF STRUCTURE
B) ACCESSING OF STRUCTURE ELEMENT
A) DECLARATION OF STRUCTURE: FOR CREATING A STRUCTURE BE USE STRUCT STATEMENT. THE GENERAL SYNTAX TO CREATE STRUCTURE.
STRUCT <TAGNAME>
{
DATATYPE1 MEMBER VARIABLE1
DATATYPE N MEMBER VARIABLE
};
EX: STRUCT BOOK
{
CHAR P[20];
INT ROLLNO;
FLOAT FEES;
};

B) ACCESSING OF STRUCTURE ELEMENT: WE CAN EASILY ACCESS MEMBER VARIABLE BY USING
STRUCTURE VARIABLE:
EX: STRUCT STD
{
INT A;
INT B;
CHAR P1[20];
}A1,B1,A2; //TYPE –I STRUCTURE VARIABLE DECLARATION
STRUCT STD P1,P2,P3; //TYPE – II STRUCTURE VARIABLE DECLARATION

STORAGE OF STRUCTURE IN MEMORY: STRUCTURE ELEMENTS ARE ALWAYS STORED IN CONTIGUOUS
MEMORY LOCATIONS. EXAMPLE IS-:
void main() {
struct book {
char name;
float price;
int pages; };
struct book b1={'b',130.00,550};
clrscr();
printf("n address of name %u",&b1.name);
printf("n address of price -: %u",&b1.price);
printf("n address of pages -%u",&b1.pages);
getch(); }

STORAGE OF STRUCTURE IN MEMORY:

COPY OF STRUCTURE ELEMENT IN C: STRUCTURE ELEMENTS CAN BE COPIED EITHER PIECE-MEAL OR ALL AT ONE SHOT. BOTH
THESE APPROACHES ARE SHOWN IN THE FOLLOWING EXAMPLE:
void main() { struct book {
char name[10]; float price; int pages; };
struct book b1={"vivek",123.34,550}; struct book b2,b3;
clrscr();
strcpy(b2.name,b1.name);
b2.price=b1.price;
b2.pages=b1.pages;
b3=b2; //copying structure variable
printf("n %s n %f n %d",b1.name,b1.price,b1.pages);
getch(); }

NESTED STRUCTURE IN C: ONE STRUCTURE CAN BE NESTED WITHIN ANOTHER STRUCTURE. USING THIS
FACILITY , COMPLEX DATA TYPES CAN BE CREATED. THE FOLLOWING PROGRAM SHOWN NESTED
STRUCTURE AT WORK:
void main() {
struct student {
char name[20],subject[20];int age; };
struct book {
char bname[20]; int bid;
struct student e; };
struct book b1={"let us c",101,"vivek","C programming",10};
clrscr();
printf("n bname=%s n bid=%d name=%s n subject=%s n
age=%d",b1.bname,b1.bid,b1.e.name,b1.e.subject,b1.e.age); getch();
}

ARRAY OF STRUCTURE IN C: WE KNOW THAT WE CAN CREATE ARRAY WITH IN STRUCTURE & WE CAN ALSO
CREATE STRUCTURE VARIABLE AS ARRAY. IN WHICH WE CAN STORE NO OF RECORDS IN ROWS. IF YOU ARE
CREATING STRUCTURE VARIABLE OF ARRAY THAT YOU DON’T HAVE TO CREATE ALL STRUCTURE VARIABLE
AS ARRAY EXCEPT CHARACTER.
EX: void main() {
struct stud{ char name[20]; int age; }b1[3];//array of structure
int i; clrscr();
for(i=0;i<2;i++) {
printf("n enter student name-:");
scanf("%s",&b1[i].name);
printf("n enter age-:");
scanf("%d",&b1[i].age);}
for(i=0;i<2;i++) {
printf("n name is-: %s",b1[i].name);
printf("n age is -: %d",b1[i].age); }
getch(); }

Union in C: union are derived data types , the way structures are : union and structure look alike , but are
arranged in totally different activity.
A structure enables us treat a number of different variables stored at different places in memory. Unlike
this a union enables us to treat the same space in memory as a number of different variables.
#include<conio.h> #include<stdio.h>
void main() { union book {
int bid; float p; } b1;
struct book1 { int bid1; float p1; } b2;
clrscr(); printf("n Enter two number first for union and second for structure-:");
scanf("%d%d",&b1.bid,&b2.bid1);
printf("n %dn %d",b1.bid,b2.bid1);
printf("n Enter two float value first union and second structure-:");
scanf("%f%f",&b1.p,&b2.p1);
printf("n %fn %f",b1.p,b2.p1);
getch(); }

C Structure and Union in C

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