structures_notes.md

Structures in C

What is a Structutre?

• A structure is a user defined data type in C. A structure creates a data type that can be used to group items of possibly different types into a single type.

Array Vs Structure

• An array is a collection of variables of same data type whereas a structure is a collection of variables of different data type.

Defining a Structure

To define a structure, you must use the struct statement. The struct statement defines a new data type, with more than one member. The format of the struct statement is as follows:

struct [structure_name] {

   member definition;
   member definition;
   ...
   member definition;
} [one or more structure variables];

Example of defining a structure:

struct Books {
   char  title[50];
   char  author[50];
   char  subject[100];
   int   book_id;
} book;

Accessing Structure Members

To access any member of a structure, we use the member access operator (.). You would use the keyword struct to define variables of structure type. The following example shows how to use a structure in a program:

#include <stdio.h>
 
struct Student {
   char  Name[50];
   char  Class[50];
   int   RollNo;
   int   Age;
   float Height;
};
 
int main( ) {

   struct Student St1;        /* Declare St1 of type Student */

   /* Student1 data entry */
   printf("Enter Student data: \n");
   printf("Name: ");
   scanf("%s", St1.Name); 
   printf("Class: ");
   scanf("%s", St1.Class); 
   printf("Roll No: ");
   scanf("%d", &St1.RollNo); 
   printf("Age: ");
   scanf("%d", &St1.Age); 
   printf("Height (in cm): ");
   scanf("%f", &St1.Height); 

   /* print Student1 info */
   printf( "Student 1 Name : %s\n", St1.Name);
   printf( "Student 1 Class : %s\n", St1.Class);
   printf( "Student 1 Roll No : %d\n", St1.RollNo);
   printf( "Student 1 Age : %d\n", St1.Age);
   printf( "Student 1 Height : %f\n", St1.Height);
return 0;
}

Example 2, adding complex numbers using structures:

#include<stdio.h>
struct comp{
    float real;
    float imag;
};
struct comp comp1,comp2;
int main(){
    struct comp result;
    printf("Enter Complex Number 1: ");
    scanf("%f%f",&comp1.real, &comp1.imag);
    printf("Enter Complex Number 2: ");
    scanf("%f%f",&comp2.real,&comp2.imag);
    result.real = comp1.real + comp2.real;
    result.imag = comp1.imag + comp2.imag;
    printf("The sum is %.2f + i%.2f\n", result.real,result.imag);
    return 0;
}

Array of Structures

An array of structres in C can be defined as the collection of multiple structures variables where each variable contains information about different entities. The array of structures in C are used to store information about multiple entities of different data types. The array of structures is also known as the collection of structures.

Example:

    #include<stdio.h>  
    struct student{    
    	int rollno;    
    	char name[10];    
    };    
    int main()
    {    
    	int i;    
    	struct student st[5];    
    	printf("Enter Records of 5 students");    
    	for(i=0;i<5;i++)
	{    
    		printf("\nEnter Rollno: ");    
    		scanf("%d",&st[i].rollno);    
    		printf("\nEnter Name: ");    
    		scanf("%s",&st[i].name);    
	}	    
    	printf("\nStudent Information List:");    
    	for(i=0;i<5;i++)
	{    
    		printf("\nRollno:%d, Name:%s \n",st[i].rollno,st[i].name);    
    	}    
        return 0;    
    }