pointers in c or c++

Strings are used for storing text.

A string variable contains a collection of characters surrounded by double quotes:

Example

Create a variable of type string and assign it a value:

string greeting = "Hello";

To use strings, you must include an additional header file in the source code, the <string> library:

Example

// Include the string library#include <string>

// Create a string variablestring greeting = "Hello";

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String Concatenation

The + operator can be used between strings to add them together to make a new string. This is called concatenation:

Example

string firstName = "John ";
string lastName = "Doe";
string fullName = firstName + lastName;
cout << fullName;

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In the example above, we added a space after firstName to create a space between John and Doe on output. However, you could also add a space with quotes (" " or ' '):

Example

string firstName = "John";
string lastName = "Doe";
string fullName = firstName + " " + lastName;
cout << fullName;

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Append

A string in C++ is actually an object, which contain functions that can perform certain operations on strings. For example, you can also concatenate strings with the append() function:

Example

string firstName = "John ";
string lastName = "Doe";
string fullName = firstName.append(lastName);
cout << fullName;

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It is up to you whether you want to use + or append(). The major difference between the two, is that the append() function is much faster. However, for testing and such, it might be easier to just use +.

Adding Numbers and Strings

WARNING!

C++ uses the + operator for both addition and concatenation.

Numbers are added. Strings are concatenated.

If you add two numbers, the result will be a number:

Example

int x = 10;
int y = 20;
int z = x + y;      // z will be 30 (an integer)

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If you add two strings, the result will be a string concatenation:

Example

string x = "10";
string y = "20";
string z = x + y;   // z will be 1020 (a string)

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If you try to add a number to a string, an error occurs:

Example

string x = "10";
int y = 20;
string z = x + y;

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String Length

To get the length of a string, use the length() function:

Example

string txt = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
cout << "The length of the txt string is: " << txt.length();

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Tip: You might see some C++ programs that use the size() function to get the length of a string. This is just an alias of length(). It is completely up to you if you want to use length() or size():

Example

string txt = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
cout << "The length of the txt string is: " << txt.size();

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Access Strings

You can access the characters in a string by referring to its index number inside square brackets [].

This example prints the first character in myString:

Example

string myString = "Hello";
cout << myString[0];
// Outputs H

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Note: String indexes start with 0: [0] is the first character. [1] is the second character, etc.

This example prints the second character in myString:

Example

string myString = "Hello";
cout << myString[1];
// Outputs e

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Change String Characters

To change the value of a specific character in a string, refer to the index number, and use single quotes:

Example

string myString = "Hello";
myString[0] = 'J';
cout << myString;
// Outputs Jello instead of Hello

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