STRINGS:

STRINGS:

Strings are sequence of characters enclosed in double quotes is considered as string. By default a string gets terminated with null character (\0) marking the end of the string and that character is not visible to the user.

Whereas a character is enclosed in single quote and it is not terminated with any default character.

For e.g., printf(“welcome to strings”);  // “welcome to strings” is string constant.

Declaration of string variables:

char  stringname[size];

The declaration of string variable is very much similar to declaring a character array. The general form is shown below: 

               for e.g.,   char name[20];  

where  name is the name of the string.

Initialization of string to character array:

The general form of initializing string to character array is shown below:

char stringname[size]=”value”;

where value can be sequence of characters.

For e.g.,  char name[20]=”learn strings”;

From the above declaration,”name” is the name of the string or character array and “learn strings” is the value initialized to the character array “name”  and by default terminated with null character(\0) marking the end of the string. Below we will see how the string is initialized and also see how memory is allocated.

Name of the array	Name
index	0	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19
Value	l	e	a	r	n		s	t	r	i	n	g	s	\0

Initialization of characters to character array

For e.g.

char name[20]={‘l’,’e’,’a’,’r’,’n’,’  ‘,’s’,’t’,’r’,’i’,’n’,’g’,’s’};

initialized characters to string

char name[20]={‘l’,’e’,’a’,’r’,’n’,’  ‘,’s’,’t’,’r’,’i’,’n’,’g’,’s’,’\0’}; which is equivalent to

char name[20]=”learn strings”;

Reading a string to the character array:

If we suppose that a character array is declared as shown below:

char college_name[25];

then a string can be read using the scanf statement as shown below:

scanf(“%s”,college_name);

or

for(i=0;i<25;i++)

scanf(“%c”,&college_name[i]);

Note: No need to preceed the array name with ampersand(&) in the scanf statement and %s format specifer stands for string, no need to specify the subscript variable.

Printing a string from the character array:

 If we suppose that a character array is declared as shown below:

 char college_name[25];

 then a string can be read using the scanf statement as shown below:

 scanf(“%s”,college_name);

 and the contents of the character array can be printed as string as shown below:

printf(“%s”,college_name);

or

for(i=0;i<25;i++)

scanf(“%c”, &college_name[i]);

                         or

for(i=0;i<25;i++)

printf(“%s”,college_name[i]);

Note: No need to preceed the array name with ampersand(&) in the scanf statement and %s format specifer stands for string. no need to specify the subscript variable.

Array of Strings:

String is an array of characters and array of strings is 2-D array of characters in which each row is one string.

For e.g.,

char weekdays[7][12]={“Mon”,”Tues”,”Wed”,”Thurs”,”Fri”,”Sat”,”Sun”};

In the above example a character array by name “weekdays” is declared as 2-D array which can store 7 rows with each row of 12 characters initialized with strings.

String Library Functions:

 C supports a wide range of functions that manipulate strings. The most common are listed here:

Name  Function

strcpy(s1, s2) Copies s2 into s1

strcat(s1, s2) Concatenates s2 onto the end of s1

strlen(s1) Returns the length of s1

strcmp(s1,s2) Returns 0 if s1 and s2 are the same; less than 0 if s1<s2; greater than 0 if s1>s2

strchr(s1, ch) Returns a pointer to the first occurrence of ch in s1

strstr(s1, s2) Returns a pointer to the first occurrence of s2 in s1

These functions use the standard header <string.h>.

The following program illustrates the use of these string functions:

#include <stdio.h>

#include <string.h>

int main(void)

{

char s1[80], s2[80];

gets(s1);

gets (s2);

printf("lengths: %d %d\n", strlen(s1), strlen(s2));

if(!strcmp(s1, s2)) printf("The strings are equal\n");

strcat(s1, s2);

printf (''%s\n", s1);

strcpy(s1, "This is a test.\n");

printf(s1);

if(strchr("hello", 'e')) printf("e is in hello\n");

if(strstr("hi there", "hi")) printf("found hi");

return 0;

}

If you run this program and enter the strings "hello" and "hello", the output is

lengths: 5 5

The strings are equal

hellohello

This is a test.

e is in hello

found hi

Remember, strcmp( ) returns false if the strings are equal. Be sure to use the logical ! operator to reverse the condition, as just shown, if you are testing for equality.

Multi-dimensional arrays:

C programming language allows multidimensional arrays. Here is the general form of a multidimensional array declaration:

datatype name[size1][size2]...[sizeN];

For example, the following declaration creates a three dimensional 5 . 10 . 4 integer array:

int threedim[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 list of one-dimensional arrays. To declare a two-dimensional integer array of size x,y you would write something as follows:

type arrayName [size1][ size2 ];

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.