18 Characters and Strings.pptx - Topic 18 Characters and...

Topic 18
Characters and Strings
1

Characters
 In C/C++, character constants are written
surrounded by single quotes e.g
. 'a' or '?'
or '4' .

A variable of type char can be used to store
a single character.
char ch;
ch = 'a';
 When we want to store many characters,
we can use an array of characters.
2

Array of Characters
 Example: array to store 5 characters.
char letters[5];
letters[0] = 'a';
letters[1] = 'p';
letters[2] = 'p';
letters[3] = 'l';
letters[4] = 'e';
for(int i = 0; i < 5; i++)
cout << letters[i];
3

Character Manipulation Functions
 C++ provides a set of functions for
manipulating characters.
 To use these functions in your program,
remember to add this #include directive in
your program:
#include <cctype>
4

Character Manipulation Functions
 These functions are divided into 2 groups:
 classifying functions and

converting functions
 Classifying functions examine a character
and tell if it belongs to a given
classification.
 These functions names all start with ‘is’ and
return true or false.
5

Character Manipulation Functions
Function Description
isalpha Checks if the character is an
alphabetic character (a-z or A-Z)
isdigit Checks if the character is a digit (0-9)
isalnum Checks if the character is an
alphabetic (a-z or A-Z) or numeric (0-
9) character
Ispunct Check if character is a punctuation
character (',', '!', '?', etc)
6

Character Manipulation Functions
Function Description
isupper Checks if the character is an
uppercase alphabetic character (A-Z)
islower Checks if the character is a lowercase
alphabetic character (a-z)
isspace Checks if the character is a
whitespace ( blank space (' '),
horizontal tab ('\t'), line feed ('\n'),
vertical tab ('\v'), form feed ('\f'), or
carriage return ('\r') )
7

Character Manipulation Functions
 Character conversion functions convert a
character from one case to another.
Function Description
toupper Converts lowercase to uppercase. If
not lowercase, returns it unchanged.
tolower Converts uppercase to lowercase. If
not uppercase, returns it unchanged.
8

Character Function Examples

Example: To input a character and check if
it is an alphabet or digit.
char ch;
cout << "Enter a character: ";
cin >> ch;
if( isalpha(ch) )
cout << "It is an alphabet";
else if( isdigit(ch) )
cout << "It is a digit";
else
cout << "Not alphabet or digit";
9

Character Function Examples

Example: To convert all the characters in an
array to uppercase.
char letters[5];
letters[0] = 'a';
letters[1] = 'p';
letters[2] = 'p';
letters[3] = 'l';
letters[4] = 'e';
for(int i = 0; i < 5; i++)
letters[i] = toupper(letters[i]) ;
10

Characters and ASCII Codes

Remember that a character is represented
in the computer using ASCII code.

We can display the character using either
the character or its ASCII code in object cin.