• Can be tricky

Example of (A-1)

// instr1.cpp -- reading more than one string
#include <iostream>
int main()
{
	using namespace std;
	const int ArSize = 20;
	char name[ArSize];
	char dessert[ArSize];
 
	cout << "Enter your name:\n";
	cin >> name;
	cout << "Enter your favorite dessert:\n";
	cin >> dessert;
	cout << "I have some delicious " << dessert;
	cout << " for you, " << name << ".\n";
	return 0;
}

The intent of the program in (A-1) is simple:

• Read a user’s name and favorite dessert from the keyboard and then display the information (B-1)

Here is a sample run (A-1):

Program Notes (A-1)

• (B-1) We didn’t even get a chance to respond to the dessert prompt (B-2)
  • (B-2) The program showed it and then immediately moved on to display the final line (B-3)

• (B-3) The problem lies with how cin determines when you’ve finished entering a string (B-4)
• (B-4) You can’t enter the null character from the keyboard (B-5)
• (B-5) cin needs some other means for locating the end of a string (B-6)
• (B-6) The cin technique (B-7)
• (B-7) Is to use whitespace—spaces, tabs, and newlines—to delineate a string (B-8)
• (B-8) This means cin reads just one word when it gets input for a character array (B-9)
• (B-9) After it reads this word, cin automatically adds the terminating null character when it places the string into the array (B-10)

• (B-10) The practical result in this example (B-11)
  • (B-11) Is that cin reads Bjarne as the entire first string and puts it into the name array (B-12)
    • (B-12) This leaves poor Stroustrup still sitting in the input queue (B-13)
    • (B-13) When cin searches the input queue for the response to the favorite dessert question, it finds Stroustrup still there (B-14)
    • (B-14) Then cin gobbles up Stroustrup and puts it into the dessert array (Image-1)

(Image-1) The cin view of string input

Another problem, which didn’t surface in the sample run

• Is that the input string might turn out to be longer than the destination array
• Using cin as this example did offer no protection against placing a 30-character string in a 20-character array

• Are to initialize an array to a string constant and to read keyboard or file input into an array
• (A-1) demonstrates these approaches by initializing one array to a quoted string and using cin to place an input string in a second array
  • The program (A-1) also uses the standard library function strlen() to get the length of a string
  • The standard cstring header file (or string.h for older implementations) provides declarations for this and many other string-related functions (A-1)

Example of (A-1)

// strings.cpp -- storing strings in an array
#include <iostream>
#include <cstring> // for the strlen() function
int main()
{
	using namespace std;
	const int kSize = 15;
	char name1[kSize]; // empty array
	char name2[kSize] = "C++omputer"; // initialized array
	// NOTE: some implementations may require the static keyword
	// to initialize the array name2
 
	cout << "Howdy! I'm " << name2;
	cout << "! What's your name?\n";
	cin >> name1;
	cout << "Well, " << name1 << ", your name has ";
	cout << strlen(name1) << " letters and is stored\n";
	cout << "in an array of " << sizeof(name1) << " bytes.\n";
	cout << "Your initial is " << name1[0] << ".\n";
	name2[3] = '\0'; // null character
	cout << "Here are the first 3 characters of my name: ";
	cout << name2 << endl;
	return 0;
}

Compatibility Note (A-1)

• If your system doesn’t provide the cstring header file, try the older string.h version

Here is a sample run of the program in (A-1):

Program Notes

First, note that the sizeof operator gives the size of the entire array, 15 bytes, but the strlen() function returns the size of the string stored in the array and not the size of the array itself (B-1)

• (B-1) Also, strlen() counts just the visible characters and not the null character. Thus, it returns a value of 6, not 7, for the length of Bjarne (B-2)
• (B-2) If Stroustrup is a string, the minimum array size for holding that string is strlen(Stroustrup) + 1

 
(B-3) Because name1 and name2 are arrays, you can use an index to access individual characters in the array (B-4)

• (B-4) For example, the program uses name1[0] to find the first character in that array (B-5)
• (B-5) Also, the program sets name2[3] to the null character. That makes the string end after three characters, even though more characters remain in the array (Image-1)

 
(B-6) Note that the program in (A-1) uses a symbolic constant for the array size (B-7)

• (B-7) Often, the size of an array appears in several statements in a program (B-8)
• (B-8) Using a symbolic constant to represent the size of an array simplifies revising the program to use a different array size; you just have to change the value once, where the symbolic constant is defined

(Image-1) Shortening a string with \0