Character Classification in C++ : cctype
Last Updated :
15 Feb, 2023
Character classification in C++ is possible using functions specified in function library. These functions are included in the <cctype> header file.
Numerous functions to classify characters are discussed below:
1. isalpha(): This function returns true if the character is an alphabet else returns false. All the characters from a-z and A-Z return true according to this function.
Syntax:
int isalpha ( char c );
Example:
C++
// C++ program to demonstrate isalpha()
#include <cctype>
#include <iostream>
using namespace std;
// Driver Code
int main()
{
// initializing character array
char ch[5] = "g1";
// checking for isalpha() function
for (int i = 0; i < 2; i++) {
if (isalpha(ch[i]))
cout << ch[i] << " is alphabet" << endl;
else
cout << ch[i] << " is not alphabet" << endl;
}
}
Outputg is alphabet
1 is not alphabet
There comes two functions in the alphabet .
a. isupper(): This function returns true if the character is an upper alphabet else returns false. All the characters from A-Z return true according to this function.
Syntax:
int isupper(char c);
Example:
C++
// C++ program to demonstrate isalpha()
#include <cctype>
#include <iostream>
using namespace std;
// Driver Code
int main()
{
// initializing character array
char ch[5] = "Gg";
// checking for isupper() function
for (int i = 0; i < 2; i++) {
if (isupper(ch[i]))
cout << ch[i] << " is an upper alphabet" << endl;
else
cout << ch[i] << " is not an upper alphabet" << endl;
}
}
OutputG is an upper alphabet
g is not an upper alphabet
b. islower(): This function returns true if the character is a lower alphabet else returns false. All the characters from a-z return true according to this function.
Syntax:
int islower(char c);
C++
// C++ program to demonstrate isalpha()
#include <cctype>
#include <iostream>
using namespace std;
// Driver Code
int main()
{
// initializing character array
char ch[5] = "Gg";
// checking for islower() function
for (int i = 0; i < 2; i++) {
if (islower(ch[i]))
cout << ch[i] << " is an lower alphabet" << endl;
else
cout << ch[i] << " is not an lower alphabet" << endl;
}
}
OutputG is not an lower alphabet
g is an lower alphabet
2. isalnum(): This function returns true if the character is an alphabet or a number else returns false. All the characters from a-z, A-Z, and all numbers return true according to this function.
Syntax:
int isalnum ( char c );
Example:
C++
// C++ program to demonstrate isalnum()
#include <cctype>
#include <iostream>
using namespace std;
// Driver Code
int main()
{
// initializing character array
char ch[5] = "g1";
// checking for isalnum() function
for (int i = 0; i < 2; i++) {
if (isalnum(ch[i]))
cout << ch[i] << " is alphanumeric" << endl;
else
cout << ch[i] << " is not alphanumeric" << endl;
}
}
Outputg is alphanumeric
1 is alphanumeric
3. isdigit(): This function returns true if the character is a number else returns false. All Numbers return true according to this function.
Syntax:
int isdigit ( char c );
Example:
CPP
// C++ program to demonstrate isdigit()
#include <cctype>
#include <iostream>
using namespace std;
int main()
{
// initializing character array
char ch[5] = "g1";
// checking for isdigit() function
for (int i = 0; i < 2; i++) {
if (isdigit(ch[i]))
cout << ch[i] << " is digit" << endl;
else
cout << ch[i] << " is not digit" << endl;
}
}
Outputg is not digit
1 is digit
4. isblank(): This function returns true if the character is a space or tab else returns false.
Syntax:
int isblank ( char c );
Example:
C++
// C++ program to demonstrate isblank()
#include <cctype>
#include <iostream>
using namespace std;
// Driver Code
int main()
{
// initializing character array
char ch[4] = " \n\t";
// checking for isblank() function
for (int i = 0; i < 3; i++) {
if (isblank(ch[i]))
cout << " Character is blank" << endl;
else
cout << " Character is not blank" << endl;
}
}
Output Character is blank
Character is not blank
Character is blank
5. isspace(): This function returns true if the character is a space or tab or whitespace control code ( Eg.\n,\r ) else returns false.
Syntax:
int isspace ( char c );
Example:
C++
// C++ program to demonstrate isspace()
#include <cctype>
#include <iostream>
using namespace std;
// Driver Code
int main()
{
// initializing character array
char ch[4] = " \n\t";
// checking for isspace() function
for (int i = 0; i < 3; i++) {
if (isspace(ch[i]))
cout << " Character is space" << endl;
else
cout << " Character is not space" << endl;
}
}
Output Character is space
Character is space
Character is space
6. iscntrl(): This function returns true if the character is tab or any control code else returns false.
Syntax:
int iscntrl ( char c );
Example:
CPP
// C++ program to demonstrate iscntrl()
#include <cctype>
#include <iostream>
using namespace std;
// Driver Code
int main()
{
// initializing character array
char ch[4] = " \n\t";
// checking for iscntrl() function
for (int i = 0; i < 3; i++) {
if (iscntrl(ch[i]))
cout << " Character is control code " << endl;
else
cout << " Character is not control code"
<< endl;
}
}
Output Character is not control code
Character is control code
Character is control code
7. isprint(): This function returns true if the character is printable on the console i.e. all characters except control code else return false.
Syntax:
int isprint ( char c );
Example:
C++
// C++ program to demonstrate isprint()
#include <cctype>
#include <iostream>
using namespace std;
// Driver Code
int main()
{
// initializing character array
char ch[6] = "\t@gf1";
// checking for isprint() function
for (int i = 0; i < 5; i++) {
if (isprint(ch[i]))
cout << ch[i] << " is printable character "
<< endl;
else
cout << ch[i] << " is not printable Character"
<< endl;
}
}
Output is not printable Character
@ is printable character
g is printable character
f is printable character
1 is printable character
8. isxdigit(): This function returns true if character is hexadecimal i.e 0-9 and a-f else returns false.
Syntax:
int isxdigit ( char c );
Example:
C++
// C++ program to demonstrate isxdigit()
#include <cctype>
#include <iostream>
using namespace std;
// Driver Code
int main()
{
// initializing character array
char ch[6] = "\t@gf1";
// checking for isxdigit() function
for (int i = 0; i < 5; i++) {
if (isxdigit(ch[i]))
cout << ch[i] << " is hexadecimal Character"
<< endl;
else
cout << ch[i] << " is not hexadecimal Character"
<< endl;
}
}
Output is not hexadecimal Character
@ is not hexadecimal Character
g is not hexadecimal Character
f is hexadecimal Character
1 is hexadecimal Character
9. ispunct(): This function returns true if the character is punctuation mark else returns false.
Syntax:
int ispunct ( char c );
Example:
CPP
// C++ program to demonstrate ispunct()
#include <cctype>
#include <iostream>
using namespace std;
// Driver Code
int main()
{
// initializing character array
char ch[6] = "\t@gf1";
// checking for ispunct() function
for (int i = 0; i < 5; i++) {
if (ispunct(ch[i]))
cout << ch[i] << " is punctuation mark" << endl;
else
cout << ch[i] << " is not punctuation mark"
<< endl;
}
}
Output is not punctuation mark
@ is punctuation mark
g is not punctuation mark
f is not punctuation mark
1 is not punctuation mark
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