Standard library header <cctype>
From cppreference.com
                    
                                        
                    
                    
                                                            
                    This header was originally in the C standard library as <ctype.h>.
This header is part of the null-terminated byte strings library.
| Functions | |
| checks if a character is alphanumeric (function) | |
| checks if a character is alphabetic (function) | |
| checks if a character is lowercase (function) | |
| checks if a character is an uppercase character (function) | |
| checks if a character is a digit (function) | |
| checks if a character is a hexadecimal character (function) | |
| checks if a character is a control character (function) | |
| checks if a character is a graphical character (function) | |
| checks if a character is a space character (function) | |
| (C++11) | checks if a character is a blank character (function) | 
| checks if a character is a printing character (function) | |
| checks if a character is a punctuation character (function) | |
| converts a character to lowercase (function) | |
| converts a character to uppercase (function) | |


