One Dimensional arrays

Arrays can be classified into

• One‒Dimensional arrays

• Two‒Dimensional arrays

• Multi‒Dimensional arrays

ONE‒DIMENSIONAL ARRAYS

The collection of data items can be stored under a one variable name using only one subscript, such a variable is called the one‒dimensional array.

A one dimensional array or single dimensional array is a type of linear array, whose elements are accessed with a single subscript, which can either represent a row or column.

1. Array Declaration

Arrays are declared in the same manner as an ordinary variables except that each array name must have the size of the array i.e., number of elements accommodated in that array.

Like variables, the array must be declared before they are used.

The subscript of an array can be integer constant, integer variable or an expression that yields an integer value.

Example:

int a[5];

int marks [5];

char name [10];

float avg [10];

Where,

'a' is the name of the array with 5 subscripts of integer data types and the computer reserves five storage locations, name is character array of 10 and avg is floating variable.

NOTE: When working with arrays, remember that the first element of an array is indexed by zero, and the last element is. indexed by the number of elements in the array minus one.

2. Features of Arrays

• An array is a derived data type. It is used to represent a collection of elements of the same data type.

• The elements can be accessed with base address (index) and the subscripts define the position of the element.

• In array, the elements are stored in continuous memory location. The starting memory location is represented by the array name and it is known as the base address of the array.

• It is easier to refer the array elements by simply incrementing the value of the subscript.

3. Processing of an Array

The entire array cannot be accessed with single operation. So, the array elements must be accessed on an element‒by‒element basis. This can be usually done with the help of the loop, when each pass of the loop is used to access an array element, thus the number of passes through the loop will therefore equal the number of array elements to be processed.

Example 1: Program to read 5 data items from input and store them in an array and display their sum.

/*Program to read 5 data and store them in an array and display their sum *

#include <stdio.h>

#include <conio.h>

void main()

{

       /* Local definitions */

       int a[5], sum=0,i;  /* 'a' is the array with 5 subscripts of integer* /

       /* Statements */

       clrscr();

       printf("Enter 5 integer numbers\n");

       for(i=1;i<=5;i++)

       {

              scanf("%d", &a[i]);

              sum=sum+a[i];

       } /* for */

       printf("The sum of given numbers is: %d\n", sum);

       getch();

} /* main */

OUTPUT:

Enter 5 integer numbers

120 45 69 390

The sum of given numbers is : 669

EXPLANATION: This has an array which is ready to hold 5 integer elements, the loop established to accept 5 numbers, while reading from input each time the subscript of an array varies depending upon loop variable and calculating their sum.

4. Array Initialisation

The values can be initialised to an array, when they are declared like ordinary variables, otherwise they hold garbage values.

The array can be initialized in the following two ways:

i) At compile time

ii) At run time

i) At compile time

Syntax: data type array_name[size] ={ List of values };

Description: The list of values must be separated by commas.

Example: int marks[3]= {70,80,90};

This statement declares the variable marks as an array of 3 elements and will be assigned to values specified in list as shown below.

Like ordinary variables, the values to the array can be initialised as follows.

marks[0]=70;

marks[1]=80;

marks[2]=90;

These elements can be used like ordinary variables.

Character array can also be initialised in similar fashion.

Example:

char name[ ] = { 'L', 'A', 'K'}; = { 'Ĺ‚'A','K'};

The above statement declares the name variable as an array of character initialised with the string 'LAK'.

ii) At Run time

The array can be explicitly initialized at run time.

Example:

while (i<=10)

{

      if (i<5)

            sum[i]=0;

      else

            sum[i]=sum[i]+i;

}

EXPLANATION: The while loop checks the condition i<=10. If condition is true then if statement checks the condition i<5, if condition is true then sum[i] the assigned to zero else sum[i] assigned as sum[i]+i.

Like, the array can also be initialized by reading data item from the input.

Example:

int n[2];

scanf("%d %d", &n[0], &n[1]);

Here array n is declared as integer type variable. n[0], n[1] it reads through the scanf() function.

We can assign initial values to the elements of an array like just as you can assign initial values to variables when they are declared. This is done by simply listing the initial values of the array, starting from the first element. Values in the list are separated by commas and the entire list is enclosed in a pair of braces.

The statement int A[5] = { 0, 0, 0, 0, 0 }; declares an array called A to contain five integer values and initializes each of these elements to zero. In a similar fashion, the statement int B[5] = {1, 2, 3, 4, 5} sets the value of B[0] to 1, B[1] to 2, B[2] to 3, and so on.

Arrays of characters are initialized in a similar manner; thus the statement char characters[5] = { 'a', 'b', 'c', 'd', 'e' }; defines the character array letters and initializes the five elements to the characters ‘a', 'b', 'c', 'd', and 'e' respectively.

It is not necessary, to completely initialize an entire array. If fewer initial values are specified, only an equal number of elements are initialized. The remaining values in the array are set to zero. The figure below shows, how the arrays can be initialised.

Example:

 float data[100] = {10, 20, 30};

The above initializes the first three values of data to 10, 20, and 30, and sets the remaining 97 elements to zero.

Example: Initializing Arrays

#include <stdio.h>

int main(void)

{

        int values[10] = {1, 2, 3, 4, 5 };

        int i;

        for (i = 5; i < 10; ++i)

                values[i] = i * i;

        for (i = 0; i < 10; ++i)

                printf ("array values[%i] = %i\n", i, values[i]);

return 0;

}

5. Entering data into the array

The data can be entered into an array using the input statement as well as loop statements.

Example 1: Program to accept 5 numbers and print whether the number is even or odd.

/* Program to print whether the number is odd or even */

#include <stdio.h>

#include <conio.h>

void main()

{

     int a[5],i;   /* Local definitions */

     for(i=0;i<5;i++)

     {

          printf("Enter the %d number: ",i+1);

          scanf("%d", &a[i]);

     } /* for */

     for(i=0;i<5;i++)

     {

          if(a[i]%2==0)

          printf("%d Number is even. \n",a[i]);

          else

          printf("%d Number is odd. \n",a[i]);

     } /* for */

     getch();

} /* main */

INPUT:

Enter the 1 number: 17

Enter the 2 number: 38

Enter the 3 number: 79

Enter the 4 number: 80

Enter the 5 number: 76

OUTPUT:

17 Number is odd

38 Number is even

79 Number is odd

80 Number is even

76 Number is even

EXPLANATION: This program reads 5 integers into an array, then read array values one by one and evaluate whether the number is even or odd number and print them.

Example 2: Program to sort the given strings alphabetically.

/* Program to sort the given strings alphabetically */

#include <stdio.h>

#include <conio.h>

#include <ctype.h>

void main()

{

        int i,j;

        char b[20];

        printf("Enter the text to sort : ");

        gets (b);

        printf("Sorted Text are: ");

        for(i=65;i<=90;i++)

        {

                for(j=0;j<30;j++)

                {

                        if(b[j]==toupper(i) || b[j]==tolower(i))

                        printf("%c", b[j]);

                } /* for */

        } /* for */

        getch();

} /* main */

OUTPUT:

Enter the text to sort: VRBPublishers

Sorted Text are : BbehilPRrssuV

EXPLANATION: The above program gets the string characters from the keyboard. ASCII equivalents of alphabets are used to sort out the given string. The toupper() and tolower() string functions in if statement used to ignore the priority of characters i.e., capital or small letters are treated the same. If the character value given by for loop i and string b[] value denoted by for loop j are same that value gets printed. Because the value of a character supplied by the outer for loop are taken alphabetically.