Arrays in 'C' Language

Array in 'C' Language: 

• Array is a collection of more than one elements having same data type.
• Elements having same data type are called as homogeneous elements.
• We can also say that array is a list of elements. 
• There are three types of arrays :

1) One-dimensional Array : 

• An array which store its elements into a single row is called one dimensional array.
• This dimension is basically row.

2) Two-dimensional Array : 

• An array which store its elements using row and column (two dimensions) that means in tabular or matrix form is called two-dimensional array.
• These two dimensions are basically row and colum.

3) Multi-dimensional Array : An array which have more than two dimensions to store its elements is called multi-dimensional array.

Array Operations :

• We can perform three basic operations with an array variable such as declaring array, initializing array and accessing elements of an array.
• Way of performing these operations is as below

Declaration of Array : 

• Since 'C' is a compiled language we must declare an array before using it.
• An array can be declared by using following syntax 

     data_type array_name[size];
 Where
     data_type specifies type of elements that       we want to store into array.
     array_name indicates name of array it is       an identifier.
     size specifies no of elements that can be         stored into respective array.

• For example int num[20]; determines that num is an array of type integer with size 20 that means num can store 20 integer values in it.
• For 2-D array syntax is 

     data_type array_name[row][col];
 Where
     data_type specifies type of elements that       we want to store into array.
     array_name indicates name of array it is       an identifier.
     row specifies no. of rows in array.
     col specifies no. of  columns in array.


Initialization of Array : 

• Array can be initialized at the time of declaring array itself or after declaration.
• Every element of array has an index.
• Array index always starts with 0.
• We can assign multiple values to array indices at a time or can assign single element to array index individually.
• Syntax : 

     data_tye array_name[size]={ value1,value2,value3,....};
           Or
     array_name[index] = value;

• For example : 

      int num[5]={10,20,30,45,56};

• Here we are storing 5 elements into array num while declaring it.
• Now consider 

     int num[5];
     num[0]=10;
     num[1]=20;
     num[2]=30;
     num[3]=45;
     num[4]=56;

• Here we store array elements individually. Both of the above two examples results in same array.

Accessing elements of an Array :

• Array elements can be accessed by using index of array element.
• Syntax : array_name[index];
• We can also iterate through array by using loop.

Example : Consider following programs

Program 1: 

int main()

{

   int num[5]={10,20,30,45,56};

   printf(" %d  ",num[2];

   return 0;

}

Output :

 30

Program 2:

int main()

{

   int num[5]={10,20,30,45,56};

   int i;

   for(i=0;i<=4;i++)

     printf("%d\n ",num[i]);

   return 0;

}

Output :

10

20

30

45

56


Memory Representation of a Two-Dimensional Array : 

• Array elements always gets stored at a consecutive (Sequencial or serial) memory allocations.
• Name of array always represents a base address (starting address or address of element at 0th position) of an array.
• There are two ways how computer system stores an array elements into memory.
• Those ways are called as row major form and column major form of memory allocation.
• In row major form elements of array gets stored at consecutive memory locations row-wise.
• Where as in column major form elements of array gets stored at consecutive memory locations column-wise.
• For example : Consider two dimensional array as 

     int num[2][3]={(2,4,6),(13,3,7)};                 An array with two rows and three columns.

 Assume that base address of array is 100   then in row major form elements will gets   stored as :

In column major form above array will get stored as :

Passing Array to Function as an Argument :

• We can also pass entire array to function as a argument to perform operations on it.
• Consider following program to find maximum element of array 

Output :

Note : Similarly we can write program to find minimum element of an array do it as an assignment.

                

(Applications of Array)