-Arrays are defined in much the same manner as ordinary variables, except that each array name must be accompanied by a size specification (i.e., the number of elements).

-An array is a collection of variables of the same type that are referred to through a common name. A specific element in an array is accessed by an index.

-An array is a group of related data items that share a common name.

-The individual values are called elements. The elements are:  a[0], a[1], a[2] .......a[9].

-The name of the array(a) contains the address of the first location i.e., a[0].

-The elements are stored in continuous memory locations during compilation.

-The elements of the array are physically and logically adjacent. When an array is passed as an argument to a function, its address is actually passed.

-The lowest address corresponds to the first element and the highest address to the last element.

-For a one-dimensional array, the size is specified by a positive integer expression(size), enclosed in square brackets. The expression is usually written as a positive integer constant.

-In general terms, a one-dimensional array definition may be expressed as

  storage_class   data_type   array[ expression] ;

-The storage-class is optional, default values are automatic(auto) for arrays that are defined within a function or a block, and external( extern)for arrays that are defined outside of a function.

Eg: Several typical one-dimensional array definitions are shown below.

   int x[100];

  char  text[80];

  static char message[25];

  static float n[12];

Integer arrays

                                                                                           int a[10];

/*defines an array a of size 10, as a block of 10 contiguous elements in memory */

    

Character Arrays

char name[11];

-To define a character array, need to define an array of size n+1 characters. This is because all character arrays are terminated by a NULL character (“\0”).

-Where name[0] through name[9] will contain the characters comprising the name, and name[10] will store the NULL character.

Types of Arrays

Basically, arrays can divide into two types. They are:

  1. One Dimensional Array:

  - An array with only one subscript is called a one-dimensional array or 1- d array. It is used to store a list of values, all of which share a common name and are separable by subscript values.

2. Two Dimensional Array:

  - An array with two subscripts is termed a two-dimensional array.

  - A two-dimensional array, it has a list of given variable-name using two subscripts. We know that a one-dimensional array can store a row of elements, so, a two-dimensional array enables us to store multiple rows of elements.

One-dimensional Arrays:

-The general form of declaring a one-dimensional array is

  data_type     array_name [size];

-Where data-type refers to any data type supported by C, array-name should be a valid C identifier, the size indicates the maximum number of storage locations (elements) that can be stored.

The general form of initializing an array of one-dimension is as follows:

  data_type     array_name [size] = {list of values};

-The values in the list are separated by commas.

-One array is used to store a group of values. A loop (using, for loop) is used to access each value in the group.

Two-dimensional array:

-An array with two subscripts is termed a two-dimensional array.  

Eg:   int a[] [];

-A two-dimensional array, it has a list of given variable -name using two subscripts. We know that a one-dimensional array can store a row of elements, so, a two-dimensional array enables us to store multiple rows of elements.  

Eg: A table of elements or a Matrix representation.

-The syntax of declaring a two-dimensional array is:

  data_type   array_name [rowsize] [ colsize];

-Row size and column size should be integer constants.

-Total number of location allocated = (row size * column size).

-Row-number range from 0 to rowsize-1 and column-number range from 0 to colsize-1.  

Eg: int m[3] [3];

Applications of Arrays:

1. Arrays are used to store a list of values.

2. Arrays are used to Perform Matrix Operations ( Addition, Multiplication & Transpose)

3. Arrays are used to implement Search Algorithms. ( Linear Search & Binary Search).

4. Arrays are used to implement Sorting Algorithms ( Insertion Sort, Bubble Sort, Selection Sort, Quick Sort, Merge Sort, etc.,).

5. Arrays are used to implement Data structures ( Stacks & Queues).

6. Arrays are also used to implement CPU Scheduling Algorithms.