The C language
provides a capability that enables the user to define a set of ordered data
items known as an array.
What is an array?
Arrays are collection of similar items (i.e.
ints, floats, chars) whose memory is allocated in a contiguous block of memory.
Declaration of arrays
Arrays must be declared before they
are used like any other variable.
The general form of declaration is:
<data-type> variable-name[SIZE];
Example: int a[10] ;
the above array can be represented as :
a: a[0] a[1] a[2] a[3] a[4] a[5] a[6] a[7] a[8] a[9]
|
0
|
1
|
2
|
3
|
4
|
5
|
6
|
7
|
8
|
9
|
The data type specify the type of
the elements that will be contained in the array, such as int,float or char and
the size indicate the maximum number of elements that can be stored inside the
array.
For example, to declare an integer
array which contains 100 elements we can do as follows:
int a[100];
There are some
rules on array declaration.
The array name has
to follow the rule of variable and the size of array has to be a positive
constant integer.
We can access
array elements via indexes array_name[index]. Indexes
of array starts from 0 not 1 so the highest elements of an array is array_name[size-1].
Initializing
Arrays:
It is like a
variable, an array can be initialized. To initialize an array, we provide
initializing values which are enclosed within curly braces in the declaration
and placed following an equals sign after the array name.
Here is an example of initializing
an integer array.
int list[5] = {2,1,3,7,8};
The following program to count the no of positive and
negative numbers
/* Program to count the no of positive and negative
numbers*/
#include< stdio.h >
main( )
{
int a[50],n,count_neg=0,count_pos=0,i;
printf(“Enter the size of the array\n”);
scanf(%d,&n);
printf(“Enter the elements of the array\n”);
for (i=0;i < n;i++)
scanf(%d,&a[i]);
for(i=0;i < n;i++)
{
if(a[i]< 0)
count_neg++;
else
count_pos++;
}
#include< stdio.h >
main( )
{
int a[50],n,count_neg=0,count_pos=0,i;
printf(“Enter the size of the array\n”);
scanf(%d,&n);
printf(“Enter the elements of the array\n”);
for (i=0;i < n;i++)
scanf(%d,&a[i]);
for(i=0;i < n;i++)
{
if(a[i]< 0)
count_neg++;
else
count_pos++;
}
printf(“There are %d negative numbers in the
array\n”,count_neg);
printf(“There are %d positive numbers in the array\n”,count_pos);
}
printf(“There are %d positive numbers in the array\n”,count_pos);
}
Multidimensional
Arrays
An array with more
than one index value is called a multidimensional
array.
Often there is a
need to store and manipulate two dimensional data structure such as the
matrices & tables. Here array has two subscripts. One subscript denotes row
& the other the column.
To declare a multidimensional array we can do
follow syntax
Syntax:
<data_type> array_name[ ][ ];
Example: int m[3][3];
Here m is declared
as a matrix having 3 rows (numbered from 0 to 2) and 3 columns (numbered 0
through 2). The first element of the matrix is m[0][0] and the last row last
column is m[2][2].
Example:
int
table[2][3]={0,0,0,1,1,1};
Initializes the elements of first row to zero and second row
to 1. The initialization is done row by row. The above statement can be
equivalently written as
int
table[2][3]={{0,0,0},{1,1,1}}
