Array Basic

TOPIC : ARRAY

Array is used to store collection of variables of same data type. It may be single dimensional type or multidimensional type.Arrays help a lot ,instead of defining variables again and again, use a single array with multiple variables you want to define.

It consists of contiguous memory locations, lowest address corresponds to first element in the array.

Single dimensional arrays

Syntax:

type arrayname[ array size] = {};

Type: type can be any c++ data type
Array size: array size must be integer constant greater than zero
Array name: valid c++ identifier

Example:   int x[1]={10};             ==>  Note:   x is an array of one integer with array size one.
Example:   int x[10];                     ==>  Note:   here x is an array of 10 integers
                 you can assign integers values to this example through For loop
                 for(int i =0 ; i< 10 ; i++)    
                 {
                     x[i]= i + 2;
                 }
arrays integers value will b 2,3,4,5,6,7,8,9,10,11

Initialization: Arrays can be initialize in two ways weather one by one as in above example or using a single statement.

Example using single statement:
int x[5] = {1,2,3,4,5};           

Example without Array size:
int x[ ]  = {1,2,3,4,5};            ==>  Note:  it is also correct but the difference is array size is undefined


Array index:
Every element in the array has its number called index number. Lowest number 0 is called base index. It means first element in the array has its index number 0. Starts from 0 and then goes on to 1,2,3 ....
Now the question is what is advantage of index number and how can we use it. Lets take an example,

Example:
int x[5] = {10,20,30,40,50};          

now let say i want to assign a value 40 in the array to a variable z of type integer , i define like this using its index number. The index numbers for above array are these

Array elements	Index number
10	0
20	1
30	2
40	3
50	4

using index number of 40 that is 3 ,
int z = x[3];

Program code:

Multi Dimensional Arrays

Syntax:

type array_name [size 1] , [size 2] , ... , [size n];

Example:  for three dimensional array

int threedim[5][6][2];

Two Dimensional Arrays:

Two dimensional arrays are the simplest form of multi-dimensional arrays

Syntax:

type array_name [size 1] [size 2];

Array name              : valid c++ identifier

Type                         :  valid c++ data type

[size 1][size 2]          :  two dimensional array size 

Two dimensional arrays can be easily understand if you consider it as a table which has size 1 number of rows and size 2 number of columns.Look at this example

Example:     

                     int x [ 3 ][ 4 ];          ==> two dimensional array with three rows and four columns

Consider this two dimensional array as table which has three rows and four columns.

	Column 0	Column 1	Column 2	Column 3
Row 0	x [0][0]	x[0][1]	x [0][2]	x [0][3]
Row 1	x [1][0]	x [1][1]	x [1][2]	x [1][3]
Row 2	x [2][0]	x [2][1]	x [2][2]	x [2][3]

Thus every element in the array x can be identified by form x[ i ][ j ] , where i and j are can be considered as subscripts.

Initialization:
Multidimensional arrays can be initialized by specifying each row with braces separated by comma's.
Example:
int x[3][4] = { {10,20,30,40} , {50,60,70,80} , {90,100,110,120} };

It can also be initialized like this

int x[3][4]= { 10,20,30,40,50,60,70,80,90,100,110,120 };


Accessing Elements Using indexing:
From the table as shown above you can see that how element can b accessed using subscripts i.e row index and column index.

Program code: