1. CS111 Lab
Strings and classes
Instructor: Michael Gordon

2. What are classes?
 C++
was originally called “C with classes”
 A class can be thought of as new type of
variable that you can create.

Just like functions are new operations you
can write, classes are new variables
 We’ve
used one kind of class already: the
string class
 string and its functions are built into C++.

3. Strings
 The
internal construction of a string is
really an array of characters.
 To find the length of a string s we can use
the functions .length() or .size
 int x = s.length(); gives x the value of the
size of the string s.
 To “concatenate” two strings s1 and s2:

string s3 = s1+s2;

4. String examples
string first, last, name;
cout<<"Enter your first name:";
cin>>first;
cout<<"Enter your last name:";
cin>>last;
cout<<"Hi, "+first+" "+last; //concat

5. getline()
 cin
reads the typed string only until the first
whitespace.
 If you want the whole string including
those whitespaces, you can use:

getline(cin, stringname);
 cout<<“Enter
your name:”;
 getline(cin, fullname);
 Use fullname instead of first and last.

6. “dot” functions
 With
strings we start dealing with a new
kind of function call. These functions
operate on a specific “object” (an
instance of a class).
 We write the object name (e.g. the
variable name of the string) followed by
period and the function call (no space
before or after the period).

7. More functions
 s1.find(string
s2) – returns the index of the
beginning of s2 in s1.
 s1 = “hello”;
 s1.find(“lo”) – returns 3
 s1.insert(int i, string s2) – inserts s2 into s1 at
index I
 s1.at(int i) – returns the character at index
i in string s1