Arrays

                        Arrays

Let suppose, in any company-branch there are 100 employees. And we have to write a program to read and print the salary of these entire 100 employees. So in this case we will require 43 different integer variables. So as to overcome that C programming language provides a data structure called the array, which can store a fixed-size sequential collection of elements of the same type. An array is used to store a collection of data, but it is often more useful to think of an array as a collection of variables of the same type.

Instead of declaring individual variables, such as number0, number1, ..., and number99, you declare one array variable such as numbers and use numbers[0], numbers[1], and ..., numbers[99] to represent individual variables. A specific element in an array is accessed by an index.

All arrays consist of contiguous memory locations. The lowest address corresponds to the first element and the highest address to the last element.         

Note:- 1)An an array of size n the index range from 0 to n-1.

          2)Array is a collection of similar data elements( or data type).

Delclaration of array-

To declare an array in C, a programmer specifies the type of the elements and the number of elements required by an array as follows:

          type name[ size ];

This is called a single-dimensional array. The arraySize must be an integer constant greater than zero and type can be any valid C data type. For example, to declare a 10-element array called balance of type double, use this statement:

double balance[10];

initializing array:-  You can initialize array in C either one by one or using a single statement as follows:

double balance[5] = {1000.0, 2.0, 3.4, 17.0, 50.0};

The number of values between braces { } can not be larger than the number of elements that we declare for the array between square brackets [ ]. Following is an example to assign a single element of the array:

If you omit the size of the array, an array just big enough to hold the initialization is created. Therefore, if you write:

double balance[] = {1000.0, 2.0, 3.4, 17.0, 50.0};

You will create exactly the same array as you did in the previous example.

balance[4] = 50.0;

The above statement assigns element number 5th in the array a value of 50.0. Array with 4th index will be 5th ie. last element because all arrays have 0 as the index of their first element which is also called base index. Following is the pictorial representation of the same array we discussed above:

Accessing elements of the array:- An element is accessed by indexing the array name. This is done by placing the index of the element within square brackets after the name of the array. For example:

double salary = balance[9];

The above statement will take 10th element from the array and assign the value to salary variable. Following is an example which will use all the above mentioned three concepts viz. declaration, assignment and accessing arrays:

#include<stdio.h>

int main ()

{

   int n[ 10 ]; /* n is an array of 10 integers */

   int i,j;

   /* initialize elements of array n to 0 */        

   for ( i = 0; i < 10; i++ )

   {

      n[ i ] = i + 100; /* set element at location i to i + 100 */

   }

  

   /* output each array element's value */

   for (j = 0; j < 10; j++ )

   {

      printf("Element[%d] = %d\n", j, n[j] );

   }

   return 0;

}

When the above code is compiled and executed, it produces the following result:

Element[0] = 100

Element[1] = 101

Element[2] = 102

Element[3] = 103

Element[4] = 104

Element[5] = 105

Element[6] = 106

Element[7] = 107

Element[8] = 108

Element[9] = 109

Calculating the length of the array:- It is given by the total number of elements stored in it.

Length = upper_bound – lower_bound +1

Upper_bound=> index of last element.

Lower-bound=> index of first element.

Usually lower_bound=0 (zero).

8

7

5

11

13

15

Arr[0]         arr[1]        arr[2]        arr[3]          arr[4]        arr[5]

Therefore,  length=5-0+1=6