1. C - Arrays
C programming language provides a data structure called the array, which can store a fixed-size sequential
collection of elements ofthe same type. An array is used to store a collection ofdata, but it is often more useful to
think of an array as a collection of variables of the same type.
Instead of declaring individual variables, such as number0, number1, ..., and number99, you declare one array
variable such as numbers and use numbers[0],numbers[1],and ..., numbers[99]to representindividual variables.
A specific element in an array is accessed by an index.
All arrays consistofcontiguous memorylocations. The lowest address corresponds to the first element and the
highest address to the last element.
Declaring Arrays
To declare an array in C, a programmer specifies the type of the elements and the number of elements required
by an array as follows:
typearrayName[arraySize];
This is called a single-dimensional array. The arraySize must be an integer constant greater than zero
and type can be any valid C data type. For example, to declare a 10-element array called balance of type
double, use this statement:
double balance[10];
Now balance is avariable array which is sufficient to hold upto 10 double numbers.
Initializing Arrays
You can initialize array in C either one by one or using a single statement as follows:
double balance[5]={1000.0,2.0,3.4,7.0,50.0};
The number of values between braces { } can not be larger than the number of elements that we declare for the
array between square brackets [ ].
If you omit the size of the array, an array just big enough to hold the initialization is created. Therefore, if you
write:
double balance[]={1000.0,2.0,3.4,7.0,50.0};
You will create exactly the same array as you did in the previous example. Following is an example to assign a
single element of the array:
balance[4]=50.0;
The above statementassigns elementnumber 5th in the array with a value of 50.0. All arrays have 0 as the index
of their first elementwhich is also called base indexand last index of an array will be total size of the array minus
1. Following is the pictorial representation of the same array we discussed above:

2. Accessing Array Elements
An element is accessed by indexing the array name. This is done by placing the index of the element within
square brackets after the name of the array. For example:
double salary = balance[9];
The above statement will take 10th element from the array and assign the value to salary variable. Following is
an example which will use all the above mentioned three concepts viz. declaration, assignment and accessing
arrays:
#include <stdio.h>
int main ()
{
int n[ 10 ]; /* n is an array of 10 integers*/
inti,j;
/* initialize elementsofarray n to 0 */
for ( i = 0; i< 10; i++ )
{
n[ i ] = i + 100; /* setelementat location i to i + 100 */
}
/* output each array element'svalue */
for (j = 0; j < 10; j++ )
{
printf("Element[%d]=%dn",j, n[j]);
}
return 0;
}

3. Out put:
Element[0] = 100
Element[1] = 101
Element[2] = 102
Element[3] = 103
Element[4] = 104
Element[5] = 105
Element[6] = 106
Element[7] = 107
Element[8] = 108
Element[9] = 109
C Arrays in Detail
Arrays are important to C and should need lots of more details. There are following few important concepts
related to array which should be clear to a C programmer:
Concept Description
Multi-dimensional arrays
C supports multidimensional arrays.The simplestform ofthe
multidimensional arrayis the two-dimensional array.
Passing arrays to functions
You can pass to the function a pointer to an array by specifying the
array's name withoutan index.
Return array from a function C allows a function to return an array.
Pointer to an array
You can generate a pointer to the firstelementof an array by sim ply
specifying the array name,withoutany index.
Multi-dimensional Arrays in C
C programming language allows multidimensional arrays. Here is the general form of a multidimensional array
declaration:
type name[size1][size2]...[sizeN];
For example, the following declaration creates a three dimensional 5 .10 . 4 integer array:
intthreedim[5][10][4];
Two-Dimensional Arrays:
The simplest form of the multidimensional array is the two-dimensional array. A two-dimensional array is, in
essence,a listof one-dimensional arrays. To declare a two-dimensional integer array of size x,y you would write
something as follows:
typearrayName[ x ][ y ];

4. Where type can be any valid C data type and arrayName will be a valid C identifier.A two-dimensional array can
be think as a table which will have x number of rows and y number of columns. A 2-dimensional array a, which
contains three rows and four columns can be shown as below:
Thus, every element in array a is identified by an element name of the form a[ i ][ j ], where a is the name of the
array, and i and j are the subscripts that uniquely identify each element in a.
Initializing Two-Dimensional Arrays:
Multidimensional arrays maybe initialized by specifying bracketed values for each row. Following is an array with
3 rows and each row has 4 columns.
int a[3][4]={
{0,1,2,3},/* initializers for row indexed by 0 */
{4,5,6,7},/* initializers for row indexed by 1 */
{8,9,10,11}/* initializers for row indexed by 2 */
};
The nested braces, which indicate the intended row, are optional. The following initialization is equivalent to
previous example:
int a[3][4]={0,1,2,3,4,5,6,7,8,9,10,11};
Accessing Two-Dimensional Array Elements:
An element in 2-dimensional array is accessed by using the subscripts, i.e., row index and column index of the
array. For example:
intval= a[2][3];
The above statement will take 4th element from the 3rd row of the array. You can verify it in the above diagram.
Let us check below program where we have used nested loop to handle a two dimensional array:
#include<stdio.h>
int main()
{
inti,j;
// declaring and Initializing array
intarr[2][2] = {10,20,30,40};
/* Above array can be initialized as below also
arr[0][0] = 10; // Initializing array
arr[0][1] = 20;
arr[1][0] = 30;
arr[1][1] = 40;
*/
for (i=0;i<2;i++)
{
for (j=0;j<2;j++)
{
// Accessing variables

5. printf("value of arr[%d] [%d] : %dn",i,j,arr[i][j]);
}
}}
Output:
value of arr[0] [0] is 10
value of arr[0] [1] is 20
value of arr[1] [0] is 30
value of arr[1] [1] is 40
C – String
 C Strings are nothing but array of characters ended with null character (‘0’).
 This null character indicates the end of the string.
 Strings are always enclosed by double quotes. Whereas, character is enclosed by single quotes in C.
Example for C string:
 char string[20] = { ‘f’ , ’r’ , ‘e’ , ‘s’ , ‘h’ , ‘2’ , ‘r’ , ‘e’ , ‘f’ , ’r’ , ‘e’ , ‘s’ , ‘h’ , ‘0’}; (or)
 char string[20] = “fresh2refresh”; (or)
 char string [] = “fresh2refresh”;
 Difference between above declarations are, when we declare char as “string[20]“, 20 bytes of memory space is
allocated for holding the string value.
 When we declare char as “string [] “, memory space will be allocated as per the requirement during execution of the
program.
#include <stdio.h>
int main ()
{
char string[20] = "NIIT.com";
printf("The stringis : %s n", string );
return 0;
}

6. Output:
The string is : NIIT.com
C String functions:
 String.h header file supports all the string functions in C language. All the string functions are given below.
S.no
String
functions
Description
1 strcat ( ) Concatenates str2 at theend of str1.
2 strncat ( ) appends a portion of string to another
3 strcpy ( ) Copies str2 into str1
4 strncpy ( ) copies given number of characters of one string to another
5 strlen ( ) gives the length of str1.
6 strcmp ( )
Returns 0 if str1 is same as str2. Returns <0 if strl< str2. Returns >0 if
str1 > str2.
C – strcat() function
 strcat( ) function in C language concatenates two given strings. It concatenates source string at the end of destination
string. Syntax for strcat( ) function is given below.
char * strcat( char * destination,constchar * source );
 Example :
strcat ( str2, str1 ); - str1 is concatenated at the end of str2.
strcat ( str1, str2 ); - str2 is concatenated at the end of str1.
 As you know, each string in C is ended up with null character (‘0′).
 In strcat( ) operation, null character of destination string is overwritten by source string’s first character and null
character is added at the end of new destination string which is created after strcat( ) operation.
Example program for strcat( ) function in C:
 In this program, two strings “NIIT” and “C tutorial” are concatenated using strcat( ) function and result is
displayed as “C tutorial NIIT”.
#include <stdio.h>

7. #include <string.h>
int main( )
{
char source[] = " NIIT" ;
char target[ ]= " C tutorial" ;
printf ( "nSource string = %s",source ) ;
printf ( "nTarget string = %s",target ) ;
strcat ( target, source ) ;
printf ( "nTarget string afterstrcat( ) = %s", target ) ;
}
Output:
Source string = NIIT
Target string = C tutorial
Target string after strcat( ) = C tutorial NIIT
C – strncat() function
 strncat( ) function in C language concatenates ( appends ) portion of one string at the end of another string. Syntax for
strncat( ) function is given below.
char * strncat( char * destination,constchar * source,size_tnum );
 Example :
strncat( str2,str1, 3 ); – First3 characters of str1 is concatenated atthe end of str2.
strncat( str1,str2, 3 ); - First 3 characters of str2 is concatenated at the end of str1.
 As you know, each string in C is ended up with null character (‘0′).
 In strncat( ) operation, null character of destination string is overwritten by source string’s first character and null
character is added at the end of new destination string which is created after strncat( ) operation.

8. Example program for strncat( ) function in C:
 In this program, first 5 characters of the string “NIIT” is concatenated at the end of the string”C tutorial” using
strncat( ) function and result is displayed as “C tutorial fres”.
#include <stdio.h>
#include <string.h>
int main( )
{
char source[] = " NIIT" ;
char target[ ]= "C tutorial" ;
printf ( "nSource string = %s",source ) ;
printf ( "nTarget string = %s",target ) ;
strncat ( target, source,5 ) ;
printf ( "nTarget string afterstrncat( ) = %s",target ) ;
}
Output:
Source string = NIIT
Target string = C tutorial
Target string after strcat( ) = C tutorial fres
C – strcpy() function
 strcpy( ) function copies contents of one string into another string. Syntax for strcpy function is given below.
char * strcpy ( char * destination,constchar * source );
 Example:
strcpy ( str1,str2) – It copies contents ofstr2 into str1.
strcpy ( str2,str1) – It copies contents ofstr1 into str2.
 If destination string length is less than source string, entire source string value won’t be copied into destination string.

9.  For example, consider destination string length is 20 and source string length is 30. Then, only 20 characters from
source string will be copied into destination string and remaining 10 characters won’t be copied and will be truncated.
Example program for strcpy( ) function in C:
 In this program, source string “NIIT” is copied into target string using strcpy( ) function.
#include <stdio.h>
#include <string.h>
int main( )
{
char source[] = "NIIT" ;
char target[20]= "" ;
printf ( "nsource string = %s",source ) ;
printf ( "ntargetstring = %s",target ) ;
strcpy ( target, source ) ;
printf ( "ntargetstring after strcpy( ) = %s",target ) ;
return 0;
}
Output:
source string = NIIT
target string =
target string after strcpy( ) = NIIT