Characters, Strings and the String Class - C plus plus - Lecture Slides, Slides of Computer Engineering and Programming

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Characters, Strings, and the string

Class

10.1 Character Testing

• The C++ library provides several macros

for testing characters.

– Be sure to include ctype.h header file

Program 10- 1

// This program demonstrates some of the character testing // functions. #include <iostream.h> #include <ctype.h> void main(void) { char input; cout << "Enter any character: "; cin.get(input); cout << "The character you entered is: " << input << endl; cout << "Its ASCII code is: " << int(input) << endl;

Program continues

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

Program 10- 2

// This program tests a customer number to determine if it is // in the proper format. #include <iostream.h> #include <ctype.h> // Function prototype bool testNum(char []); void main(void) { char customer[8]; cout << "Enter a customer number in the form "; cout << "LLLNNNN\n"; cout << "(LLL = letters and NNNN = numbers): "; cin.getline(customer, 8);

Program continues

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

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:

ABC

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

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 <iostream.h> #include <ctype.h> void main(void) { const float pi = 3.14159; float radius; char go; cout << "This program calculates the area of a circle.\n"; cout.precision(2); cout.setf(ios::fixed);

Program continues

do { cout << "Enter the circle's radius: "; cin >> radius; cout << "The area is " << (pi * radius * radius); cout << endl; do { cout << "Calculate another? (Y or N) "; cin >> go; } while (toupper(go) != 'Y' && toupper(go) != 'N'); } while (toupper(go) == 'Y'); }

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

Program 10- 4

// This program contains string constants #include <iostream.h> void main(void) { char again; do { cout << "C++ programming is great fun!" << endl; cout << "Do you want to see the message again? "; cin >> again; } while (again == 'Y' || again == 'y'); }

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!

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