String in C++

String in C++

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.

Important points for Declaration of string

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

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.

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

	
char variable_name[SIZE];

	
char str[5];

Initializing Array string

According to array initialization concept

	
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'};

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.

	
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.

	
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.

	
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.

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

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

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

Reading String from user

	
char str[5];
cin>>str;

Note: String variable str can only take only one word. It is because when white space is encountered, the scanf() function terminates.

	
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.

Example of String program in c language

	
#include<iostream.h>
#include<conio.h>

void main()
{
char str[10];
cout<<"Enter any string: ";
gets(str);
cout<<"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.

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.