arrays and functions in c language

MODULE 3
Arrays
INTRODUCTION
Arrays: Array is a sequential collection of similar data items.
Pictorial representation of an array of 5 integers

10 20 30 40 50
A[0] A[1] A[2] A[3] A[4]

 An array is a collection of similar data items.
 All the elements of the array share a common name .
 Each element in the array can be accessed by the subscript(or index) and array name.
 The arrays are classified as:
1. Single dimensional array
2. Multidimensional array.

Single Dimensional Array.

 A single dimensional array is a linear list of related data items of same data type.
 In memory, all the data items are stored in contiguous memory locations.
Declaration of one-dimensional array(Single dimensional array)
Syntax:

datatype array_name[size];



 datatype can be int,float,char,double.
 array_name is the name of the array and it should be an valid identifier.
 Size is the total number of elements in array.
For example:
int a[5];
The above statement allocates 5*2=10 Bytes of memory for the array a.



a[0] a[1] a[2] a[3] a[4]

float b[5];

, The above statement allocatests 5*4=20 Bytes of memory for the array b.


 Each element in the array is identified using integer number called as index.
 If n is the size of array, the array index starts from 0 and ends at n-1.

Storing Values in Arrays

 Declaration of arrays only allocates memory space for array. But array elements are not initialized
and hence values has to be stored.
 Therefore to store the values in array, there are 3 methods
1. Initialization
2. Assigning Values
3. Input values from keyboard through scanf()

Initialization of one-dimensional array
 Assigning the required values to an array elements before processing is called initialization.


data type array_name[expression]={v1,v2,v3…,vn};


Where
 datatype can be char,int,float,double
 array name is the valid identifier
 size is the number of elements in array
 v1,v2,v3…......vn are values to be assigned.


 Arrays can be initialized at declaration time.
Example:
int a[5]={2,4,34,3,4};


2 4 34 3 4


a[0] a[1] a[2] a[3] a[4]


 The various ways of initializing arrays are as follows:
1. Initializing all elements of array(Complete array initialization)
2. Partial array initialization

, 3. Initialization without size
4. String initialization


1. Initializing all elements of array:
 Arrays can be initialized at the time of declaration when their initial values are known in advance.
 In this type of array initialization, initialize all the elements of specified memory size.
 Example:
int a[5]={10,20,30,40,50};
10 20 30 40 50



2. Partial array initialization
 If the number of values to be initialized is less than the size of array then it is called as partial
array initialization.
 In such a case elements are initialized in the order from 0th element.
 The remaining elements will be initialized to zero automatically by the compiler.
 Example:
int a[5]={10,20};

10 20 0 0 0

3. Initialization without size
 In the declaration the array size will be set to the total number of initial values specified.
 The compiler will set the size based on the number of initial values.
 Example:
int a[ ]={10,20,30,40,50};
 In the above example the size of an array is set to 5


4. String Initialization
 Sequence of characters enclosed within double quotes is called as string.
 The string always ends with NULL character(\0)

char s[5]=”SVIT”; We can observe that string length is 4,but size
is 5 because to store NULL character we need
one more location.

So pictorial representation of an array s is as follows:

, S V I T \0
S[0] S[1] S[2] S[3] S[4]




3.1.2 Assigning values to arrays
Using assignment operators, we can assign values to individual elements of arrays.
For example:
int a[3];
a[0]=10;
a[1]=20;
a[2]=30;

10 20 30



a[0] a[1] a[2]


Reading and writing single dimensional arrays.
To read array elements from keyboard we can use scanf() function as follows:

To read 0th element: scanf(“%d”,&a[0]);
To read 1st element: scanf(“%d”,&a[1]);
To read 2nd element: scanf(“%d”,&a[2]);
……
…….
To read n element : scanf(“%d”,&a[n-1]);
th

In general
To read ith element:
scanf(“%d”,&a[i]); where i=0; i<n; i++


To print array elements we can use printf() function as follows:

To print 0th element: printf(“%d”,a[0]);
To print 1st element: printf(“%d”,a[1]);
To print 2nd element :printf(“%d”,a[2]);
……..
……..

To nth element : printf(“%d”,&a[n-1]);
In general
To read ith element:
printf(“%d”,a[i]); where i=0; i<n;