Chapter 9

structures

What is a Structure ?

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

Syntax for creating structures

why use structures ?

We can create the data types in the Hi-Tech structure separately but when the number of properties in a structure increases it becomes difficult for us to create data variables without structures in a nut shell.

a) structures keep the data organised

b) structures make data management easy for the programmer

Array of Structures in C

Just like in a Array of integers and Array of floats and array of characters we can create an Array of structures

struct employee hytek [50]; // an array of structures

We can access the data using

hytek [0]. code = 1000;

hytek [1]. code = 1001; // and so on……

Initializing Structures

Structures can also be initialised as follows :::

struct employee Kuldeep = {1000,72.342,"Kuldeep sharma" };
struct employee happy = {1001,72.346,"happy sharma" };
struct employee ashish={0};//all elements set to 0

Structures in memory

Structures are stored in contiguous memory locations for the structure u1 of type struct hytek memory layout looks like this

In an array of structures these users data are stored adjacent to each other

Pointer to Structures

A pointer to structure can be created as follows

struct employee *ptr;

ptr = &e1;

Now we can print structure elements

printf(“%d”,*(ptr).code);

Arrow Operator

Instead of writing*(ptr).code, we can use Arrow operator to access structure properties as follows

*(ptr).code or ptr-> code
Here -> is known as the arrow operator

Passing Structures to a Function

A structure can be passed to a function just like any other data type

void show(struct employee e); //function prototype

Typedef keyword

We can use the typedef keyword to create an additional name for data type in C typedef is more commonly used with structures

#include <stdio.h &gt;>  
int main()  
{  
typedef unsigned int unit;  
unit i,j;  
i=10;  
j=20;  
printf("Value of i is :%d",i);  
printf("\nValue of j is :%d",j);  
return 0;  
}