Chapter 10

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Chapter 10

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Title: Chapter 10

1
Chapter 10 Characters, Strings, and the string
Class
2
10.1 Character Testing

The C library provides several macros for
testing characters.
Be sure to include ctype.h header file

3
Table 10-1
4
Program 10-1

// This program demonstrates some of the
character testing
// functions.
include ltiostream.hgt
include ltctype.hgt
void main(void)
char input
cout ltlt "Enter any character "
cin.get(input)
cout ltlt "The character you entered is " ltlt
input ltlt endl
cout ltlt "Its ASCII code is " ltlt int(input) ltlt
endl

5
Program continues

if (isalpha(input))
cout ltlt "That's an alphabetic character.\n"
if (isdigit(input))
cout ltlt "That's a numeric digit.\n"
if (islower(input))
cout ltlt "The letter you entered is
lowercase.\n"
if (isupper(input))
cout ltlt "The letter you entered is
uppercase.\n"
if (isspace(input))
cout ltlt "That's a whitespace character.\n"

6
Program Output With Example input

Enter any character A Enter
The character you entered is A
Its ASCII code is 65
That's an alphabetic character.
The letter you entered is uppercase.
Program Output With Other Example input
Enter any character 7 Enter
The character you entered is 7
Its ASCII code is 55
That's a numeric digit.

7
Program 10-2

// This program tests a customer number to
determine if it is
// in the proper format.
include ltiostream.hgt
include ltctype.hgt
// Function prototype
bool testNum(char )
void main(void)
char customer8
cout ltlt "Enter a customer number in the form "
cout ltlt "LLLNNNN\n"
cout ltlt "(LLL letters and NNNN numbers) "
cin.getline(customer, 8)

8
Program continues

if (testNum(customer))
cout ltlt "That's a valid customer number.\n"
else
cout ltlt "That is not the proper format of the
"
cout ltlt "customer number.\nHere is an
example\n"
cout ltlt " ABC1234\n"
// Definition of function testNum.
bool testNum(char custNum)
// Test the first three characters for
alphabetic letters
for (int count 0 count lt 3 count)

9
Program continues

if (!isalpha(custNumcount))
return false
// Test the last 4 characters for numeric digits
for (int count 3 count lt 7 count)
if (!isdigit(custNumcount))
return false
return true

10
Program Output With Example input

Enter a customer number in the form LLLNNNN
(LLL letters and NNNN numbers) RQS4567
Enter
That's a valid customer number.
Program Output With Other Example input
Enter a customer number in the form LLLNNNN
(LLL letters and NNNN numbers) AX467T9
Enter
That is not the proper format of the customer
number.
Here is an example
ABC1234

11
10.2 Character Case Conversion

The C library offers functions for converting a
character to upper or lower case.
Be sure to include ctype.h header file

12
Table 10-2
13
Program 10-3

// This program calculates the area of a circle.
It asks the
// user if he or she wishes to continue. A loop
that
// demonstrates the toupper function repeats
until the user
// enters 'y', 'Y', 'n', or 'N'.
include ltiostream.hgt
include ltctype.hgt
void main(void)
const float pi 3.14159
float radius
char go
cout ltlt "This program calculates the area of a
circle.\n"
cout.precision(2)
cout.setf(iosfixed)

14
Program continues

do
cout ltlt "Enter the circle's radius "
cin gtgt radius
cout ltlt "The area is " ltlt (pi radius
radius)
cout ltlt endl
do
cout ltlt "Calculate another? (Y or N) "
cin gtgt go
while (toupper(go) ! 'Y' toupper(go) !
'N')
while (toupper(go) 'Y')

15
Program Output With Example input

This program calculates the area of a circle.
Enter the circle's radius 10 Enter
The area is 314.16
Calculate another? (Y or N) b Enter
Calculate another? (Y or N) y Enter
Enter the circle's radius 1 Enter
The area is 3.14
Calculate another? (Y or N) n Enter

16
10.3 Review of the Internal Storage of C-strings

A C-string is a sequence of characters stored in
consecutive memory locations, terminated by a
null character.
Figure 10-1

17
Program 10-4

// This program contains string constants
include ltiostream.hgt
void main(void)
char again
do
cout ltlt "C programming is great fun!" ltlt
endl
cout ltlt "Do you want to see the message again?
"
cin gtgt again
while (again 'Y' again 'y')

18
Program 10-5

// This program cycles through a character array,
displaying
// each element until a null terminator is
encountered.
include ltiostream.hgt
void main(void)
char line80
int count 0
cout ltlt "Enter a sentence of no more than 79
characters\n"
cin.getline(line, 80)
cout ltlt "The sentence you entered is\n"
while (linecount ! '\0')
cout ltlt linecount
count

19
Program Output with Example input

Enter a sentence of no more than 79 characters
C is challenging but fun! Enter
The sentence you entered is
C is challenging but fun!

20
10.4 Library Functions for Working with C-strings

The C library has numerous functions for
handling C-strings These functions perform
various tests and manipulations.
Functions discussed in this section require the
inclusion of string.h header file

21
Figure 10-2
22
Table 10-3
23
Program 10-6

// This program uses the strstr function to
search an array
// of strings for a name.
include ltiostream.hgt
include ltstring.hgt // For strstr
void main(void)
char prods527 "TV327 31 inch
Television",
"CD257 CD Player",
"TA677 Answering Machine",
"CS109 Car Stereo",
"PC955 Personal
Computer"
char lookUp27, strPtr NULL
int index

24
Program continues

cout ltlt "\tProduct Database\n\n"
cout ltlt "Enter a product number to search for
"
cin.getline(lookUp, 27)
for (index 0 index lt 5 index)
strPtr strstr(prodsindex, lookUp)
if (strPtr ! NULL)
break
if (strPtr NULL)
cout ltlt "No matching product was found.\n"
else
cout ltlt prodsindex ltlt endl

25
Program Output With Example input

Product Database
Enter a product to search for CD257 Enter
CD257 CD Player
Program Output With Example input
Product Database
Enter a product to search for CS Enter
CS109 Car Stereo
Program Output With Other Example input
Product Database
Enter a product to search for AB Enter
No matching product was found.

26
10.5 String/Numeric Conversion Functions

The C library provides functions for converting
a C-string representation of a number to a
numeric data type, and vice-versa.
The functions in this section require the
stdlib.h file to be included.

27
Table 10-4
28
Table 10-4 Continued

Function Description
itoa Converts an
integer to a C-string. The first argument,
value, is the integer. The result
will be stored at the
location pointed to by the second
argument, string.
The
third argument, base, is an integer. It specifies
the
numbering system that the converted integer
should
be expressed in. ( 8 octal, 10 decimal,
16
hexadecimal, etc. )
Example
Usage itoa(value, string, base)

29
Program 10-7

// This program demonstrates the strcmp and atoi
functions.
include ltiostream.hgt
include ltstring.hgt // For strcmp
include ltstdlib.hgt // For atoi
void main(void)
char input20
int total 0, count 0
float average
cout ltlt "This program will average a series of
numbers.\n"
cout ltlt "Enter the first number or Q to quit "
cin.getline(input, 20)

30
Program continues

while ((strcmp(input, "Q") !
0)(strcmp(input, "q") ! 0))
total atoi(input) // Keep a running total
count // Keep track of how many numbers
entered
cout ltlt "Enter the next number or Q to quit "
cin.getline(input, 20)
if (count ! 0)
average total / count
cout ltlt "Average " ltlt average ltlt endl

31
Program Output With Example input

This program will average a series of numbers.
Enter the first number or Q to quit 74 Enter
Enter the next number or Q to quit 98 Enter
Enter the next number or Q to quit 23 Enter
Enter the next number or Q to quit 54 Enter
Enter the next number or Q to quit Q Enter
Average 62

32
10.6 Focus on Software Engineering Writing
Your Own C-string-Handling Functions

You can design your own specialized functions for
manipulating C-strings.

33
Program 10-8

// This program uses a function to copy a
C-string into an array.
include ltiostream.hgt
void stringCopy(char , char ) // Function
prototype
void main(void)
char first30, second30
cout ltlt "Enter a string with no more than 29
characters\n"
cin.getline(first, 30)
stringCopy(first, second)
cout ltlt "The string you entered is\n" ltlt second
ltlt endl

34
Program continues

// Definition of the stringCopy function.
// This function accepts two character arrays as
// arguments. The function assumes the two arrays
// contain C-strings. The contents of the second
array is
// copied to the first array.
void stringCopy(char string1, char string2)
int index 0
while (string1index ! '\0')
string2index string1index
index
string2index '\0'

35
Program Output With Example input

Enter a string with no more than 29 characters
Thank goodness its Friday! Enter
The string you entered is
Thank goodness it's Friday!

36
Program 10-9

// This program uses the function nameSlice to
"cut" the last
// name off of a string that contains the user's
first and
// last names.
include ltiostream.hgt
void nameSlice(char ) // Function prototype
void main(void)
char name41
cout ltlt "Enter your first and last names,
separated "
cout ltlt "by a space\n"
cin.getline(name, 41)
nameSlice(name)
cout ltlt "Your first name is " ltlt name ltlt endl

37
Program continues

// Definition of function nameSlice. This
function accepts a
// character array as its argument. It scans the
array looking
// for a space. When it finds one, it replaces it
with a null
// terminator.
void nameSlice(char userName)
int count 0
while (userNamecount ! ' ' userNamecount
! '\0')
count
if (userNamecount ' ')
userNamecount '\0'

38
Program Output With Example input

Enter your first and last names, separated by a
space
Jimmy Jones Enter
Your first name is Jimmy

39
Figure 10-3
40
Figure 10-4
41
Using Pointers to pass C-string arguments

Very useful
Can assume string exists from address pointed to
by the pointer up to the \0

42
Program 10-10

// This program demonstrates a function,
countChars, that counts
// the number of times a specific character
appears in a string.
include ltiostream.hgt
// Function prototype
int countChars(char , char)
void main(void)
char userString51, letter
cout ltlt "Enter a string (up to 50 characters)
"
cin.getline(userString, 51)
cout ltlt "Enter a character and I will tell you
how many\n"
cout ltlt "times it appears in the string "
cin gtgt letter
cout ltlt letter ltlt " appears "
cout ltlt countChars(userString, letter) ltlt "
times.\n"

43
Program continues

// Definition of countChars. The parameter strPtr
is a pointer
// that points to a string. The parameter ch is a
character that
// the function searches for in the string. The
function returns
// the number of times the character appears in
the string.
int countChars(char strPtr, char ch)
int times 0
while (strPtr ! '\0')
if (strPtr ch)
times
strPtr
return times

44
Program Output With Example input

Enter a string (up to 50 characters)Starting Out
With C Enter
Enter a character and I will tell you how many
times it appears in the string t Enter
t appears 4 times.

45
The C string Class

Offers ease of programming advantages over the
use of C-strings
Need to include the string header file(Notice
there is no .h extension.)
Use the following statement after the include
statements using namespace std

46
Program 10-12

// This program demonstrates the C string
class.
include ltiostreamgt
include ltstringgt // Required for the string
class
using namespace std
void main(void)
string movieTitle
string name("William Smith")
movieTitle "Wheels of Fury"
cout ltlt "My favorite movie is " ltlt movieTitle ltlt
endl
Program output
My favorite movie is Wheels of Fury

47
A note about the iostream header file

The preceding program uses the iostream header,
not iostream.h.
With some compilers, you must include the
iostream header instead of iostream.h when using
cout and cin with string objects.

48
Program 10-13 Using cin with a string object

// This program demonstrates how cin can read a
string into
// a string class object.
include ltiostreamgt
include ltstringgt
using namespace std
void main(void)
string name
cout ltlt "What is your name? " ltlt endl
cin gtgt name
cout ltlt "Good morning " ltlt name ltlt endl

49
Program Output With Example Input
What is your name? Peggy Good morning Peggy
50
Reading a line of input into a string class object

Use the getline function to read a line of input,
with spaces, into a string object. Example
codestring namecout ltlt What is your name?
getline(cin, name)

51
Comparing and Sorting string Objects

You may use the relational operators to compare
string objects
lt gt lt gt !

52
Program 10-14
// This program uses the operator to compare
the string entered// by the user with the valid
stereo part numbers.include ltiostreamgtinclude
ltstringgtusing namespace stdvoid
main(void) const float aprice 249.0, bprice
299.0 string partNum cout ltlt "The stereo
part numbers are\n" cout ltlt "\tBoom Box, part
number S147-29A\n" cout ltlt "\tShelf Model, part
number S147-29B\n" cout ltlt "Enter the part
number of the stereo you\n" cout ltlt "wish to
purchase " cin gtgt partNum cout.setf(iosfix
ed iosshowpoint) cout.precision(2)
53
Program 10-14 (continued)
if (partNum "S147-29A") cout ltlt "The price
is " ltlt aprice ltlt endl else if (partNum
"S147-29B") cout ltlt "The price is " ltlt bprice
ltlt endl else cout ltlt partNum ltlt " is not a
valid part number.\n" Program Output The
stereo part numbers are Boom Box, part
number S147-29A Shelf Model, part number
S147-29BEnter the part number of the stereo
youwish to purchase S147-29A EnterThe price
is 249.00
54
Other Ways to Declare string Objects
Declaration Example Description
string address Declares an empty string object named address.
string name(Bill Smith) name is a string object initialized with Bill Smith
string person1(person2) person1 is initialized with a copy of person2. person2 may be either a string object or a char array.
See Table 10-8 (page 589) for more examples.
55
Table 10-10 Other Supported Operators
gtgt Extracts characters from a stream and inserts them into a string. Characters are copied until a whitespace or the end of the string is encountered.
ltlt Inserts a string into a stream.
Assigns the string on the right to the string object on the left.
Appends a copy of the string on the right to the string object on the left.
Returns a string that is the concatenation of the two string operands.
Implements array-subscript notation, as in namex. A reference to the character in the x position is returned.
56
Program 10-17