The most popular library is almost certainly the string library, with perhaps
the function strlen() called most often. strlen() returns the
length of a null-terminated string. Listing below illustrates its use.
1: #include <iostream.h>
2: #include <string.h>
4: int main()
6: char buffer80];
9: cout << "Enter a string up to 80 characters: ";
11: cout << "Your string is " << strlen(buffer);
12: cout << " characters long." << endl;
13: } while (strlen(buffer));
14: cout << "\nDone." << endl;
15: return 0;
Output: Enter a string up to 80 characters: This sentence has 31 characters
Your string is 31 characters long.
Enter a string up to 80 characters: This sentence no verb
Your string is 21 characters long.
Enter a string up to 80 characters:
Your string is 0 characters long.
Analysis: On line 6, a character buffer
is created, and on line 9 the user is prompted to enter a string. As long as the
user enters a string, the length of the string is reported on line 11.
Note the test in the do...while() statement: while (strlen(buffer)).
Since strlen() will return 0 when the buffer is empty, and
since 0 evaluates FALSE, this while loop will
continue as long as there are any characters in the buffer.