In C++, a String is a sequence of characters. C++ supports two types of String representations:
- C Strings (terminated by a null character('\0'))
- Objects of string class (C++ Library provides a string class)
C Strings
String in C programming language is a one-dimensional array of characters which is terminated by a null character('\0'). A character array which is not null terminated is not a
valid C string. In a C string, each character occupies one byte of memory including null character.
Null character marks the end of the string, it is the only way for the compiler to know where this string is ending.
- "A"
- "TechCrashCourse"
- "Tech Crash Course"
- " "
Declaration of C Strings
Syntax of String Declarationchar string_name[SIZE_OF_STRING];
In the above declaration, string_name is a valid C identifier which can be used later as a reference to this string. Remember, name of an array also specifies the base address of an array.SIZE_OF_STRING is an integer value specifying the maximum number of characters which can be stored in this string including terminating null character. We must specify size of string while declaration if we are not initializing it.
For Example:char address[100]; char welcomeMessage[200];
Initialization of C Strings
Initialization of string using a character array
char name[16] = {'T','e','c','h','C','r','a','s','h','C','o','u','r','s','e','\0'};
or
char name[] = {'T','e','c','h','C','r','a','s','h','C','o','u','r','s','e','\0'};
In the above declaration individual characters are written inside single quotes('') separated by comma to form a list of characters which is wrapped in a pair or curly braces.
This list must include a null character as last character of the list.
If we don't specify the size of String then length is calculated automatically by the compiler.
char name[16] = "TechCrashCourse";or
char name[] = "TechCrashCourse";
In above declaration a string with identifier "name" is declared and initialized to "TechCrashCourse". In this type of initialization, we don’t need to put terminating null character at the end of string constant. C compiler will automatically inserts a null character('\0'), after the last character of the string literal.
C++ Program for String Initialization
#include <iostream>
using namespace std;
int main(){
char nameOne[16] = {'T','e','c','h','C','r','a','s','h','C','o','u','r','s','e','\0'};
char nameTwo[] = {'T','e','c','h','C','r','a','s','h','C','o','u','r','s','e','\0'};
char nameThree[16] = "TechCrashCourse";
char nameFour[] = "TechCrashCourse";
char *nameFive = "TechCrashCourse";
char nameSix[16];
cout << nameOne << endl;
cout << nameTwo<< endl;
cout << nameThree << endl;
cout << nameFour << endl;
cout << nameFive << endl;
// Taking string input from user
cout << "Enter a string \n";
cin >> nameSix;
cout << "You Entered : " << nameSix;
return 0;
}
Output
TechCrashCourse TechCrashCourse TechCrashCourse TechCrashCourse TechCrashCourse Enter a string C++ You Entered : C++
String Handling Standard Library Functions in C++
cstring header file contains a wide range of functions to manipulate null-terminated C strings. Below are some commonly used string handling functions of cstring header file.
| Function | Description |
|---|---|
| strlen() | It returns the length of a string. |
| strcat() | It appends one string at the end of another string. |
| strcpy() | It copies characters from one string into another string. |
| strcmp() | It compares two strings character by character. |
| strtok() | It breaks a string into smaller tokens. |
| strchr() | It searches for the first occurrence of a character in the string. |
| strstr() | It searches for the first occurrence of a string in another string. |
#include <iostream>
#include <cstring>
using namespace std;
int main(){
char input[50];
char copyString[60];
cout << "Enter a string\n";
cin >> input;
// Printing length of string using strlen()
cout << "Length of string : " << strlen(input) << endl;
// copying input into copyString
strcpy(copyString, input);
cout << "Copied String : " << copyString << endl;
// comparing input and copyString string
if(strcmp(copyString, input)){
cout << "Both Strings are Not Equal\n";
} else {
cout << "Both Strings are Equal\n";
}
return 0;
}
Output
Enter a string: TechCrashCourse Length of TechCrashCourse : 15 Copied String : TechCrashCourse Both Strings are Equal
- Null character marks the end of the C strings.
- C Strings are single dimensional array of characters ending with a null character(‘\0’).
- The ASCII value of null character('\0') is 0.
- Each character of string is stored in consecutive memory location and occupy 1 byte of memory.
- Strings constants are enclosed by double quotes and character are enclosed by single quotes.
- If the size of a C string is N, it means this string contains N-1 characters from index 0 to N-2 and last character at index N-1 is a null character.
String Class in C++
C++ provides a String class, you can also create a objects of string class for holding strings. String class supports all the operations mentioned above, additionally much more functionality.At this point may not understand about classes and object, until you understand the Object Oriented Programming Concepts(which is discussed later). Here is a sample C++ program using string class.
#include <iostream>
#include <cstring>
using namespace std;
int main () {
// Declaring objects of string class
string strOne = "C++";
string strTwo = "Programming";
string strThree;
int length;
// Reading string from user
cout << "Enter a string\n";
getline(cin, strThree);
// Printing String
cout << strThree<< endl;;
// concatenating strOne and strTwo
strOne = strOne + strTwo;
cout << "Combined String : " << strOne << endl;
// Printing length of string
length = strOne.size();
cout << "Length of Combined String : " << length << endl;
return 0;
}
Output
Enter a string TechCrashCourse TechCrashCourse Combined String : C++Programming Length of Combined String : 14