Strings

String is a collection of character or group of character, it is achieve in C language by using array character. The string in C language is one-dimensional array of character which is terminated by a null character '\0'. In other words string is a collection of character which is enclose between double cotes ( " " ).

Note: Strings are always enclosed within double quotes. Whereas, character is enclosed within single quotes in C.

Declaration of string

Strings are declared in C in similar manner as arrays. Only difference is that, strings are of char type.

Example

 
char s[5];

Initializing Array string

String are initialize into various way in c language;

Example

char str[]="abcd";
        OR
char str[5]="abcd";
        OR
char str[5]={'a','b','c','d','\0'};
        OR
char str[]={'a','b','c','d','\0'};
        OR
char str[5]={'a','b','c','d','\0'};

In c language string can be initialize using pointer.

Example

char *c="abcd";

Reading String from user

Example

 
char str[5];
scanf("%s",&str);

Example

 
#include<stdio.h>
#include<conio.h>

void main()
{
char str[10];
printf("Enter name: ");
scanf("%s",name);
printf("Your name is: %s.",name);
getch();
}

Example of reading string

 
Enter name: Hitesh kumar
Your name is: Hitesh

Note: String variable str can only take only one word. It is because when white space is encountered, the scanf() function terminates. to over come this problem you can use gets() function.

Syntax

 
char str[5];
gets(str);

gets()

gets() are used to get input as a string from keyword, using gets() we can input more than one word at a time.

puts()

puts() are used to print output on screen, generally puts() function are used with gets() function.

Example of String program

#include<stdio.h>
#include<conio.h>

void main()
{
char str[10];
printf("Enter any string: ");
gets(str);
printf("String are: ");
puts(str);
getch();
}

Explanation: Here gets() function are used for input string and puts() function are used to show string on console or monitor.

Output

Enter String: hello word
String are: hello word

C Library String functions

All the library function of String is available in String.h header file.

S.N.	Function	Purpose
1	strcpy(s1, s2)	Copies string s2 into string s1.
2	strcat(s1, s2)	Concatenates string s2 onto the end of string s1.
3	strlen(s1)	Returns the length of string s1.
4	strcmp(s1, s2)	Returns 0 if s1 and s2 are the same; less than 0 if s1<s2; greater than 0 if s1>s2.
5	strchr(s1, ch)	Returns a pointer to the first occurrence of character ch in string s1.
6	strstr(s1, s2)	Returns a pointer to the first occurrence of string s2 in string s1.

Important points for Declaration of string

• In declaration of string size must be required to mention otherwise it gives an error.

Syntax

char str[];   // Invalid
char str[10]; // Valid

• In declaration of the string size must be unsigned integer value (not -ve or zero value) which is greater than zero only.

Example

char str[];   // Invalid
char str[0];  // Invalid
char str[-1]; // Invalid
char str[10]; // Valid

Syntax

 
char variable_name[SIZE];

 
char str[5];

Important points for Initialization of the string

• In Initialization of the string if the specific number of character are not initialized it then rest of all character will be initialized with NULL.

Example

char str[5]={'5','+','A'};
    str[0];  ---> 5
    str[1];  ---> +
    str[2];  ---> A
    str[3];  ---> NULL
    str[4];  ---> NULL

• In initialization of the string we can not initialized more than size of string elements.

Example

 
char str[2]={'5','+','A','B'};  // Invalid

• In initialization of the string the size is optional in this case how many variable elements are initialized it, that array element will created.

Example

 
char str[]={'5','+','A','B'};  // Valid
sizeof(str)  --> 4byte

When we are working with character array explicitly NULL character does not occupies any physical memory at the end of the character array.

Example

char str[]={'h','e','l','l','o'};
sizeof(str)  --> 5byte

String data at the end of the string NULL character occupies physical memory.

Example

char str[]="hello";
sizeof(str)  --> 6 byte

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