Ctype.h Library functions----character manipulation functions

When used in C + +: #include <cctype>

Character Judgment function

1. isalnum function--Determines whether it is an English letter or a numeric character, if so, returns a value other than 0, or 0 if not.

Function parameter: can be a character or an integer number.

Use case: if (isalnum (CH)!=0)

Common in Windows and Linux

2, Isalpha function---Determine whether it is an English letter, if it is, then return a non-0 value, if not, then return 0.

Function parameter: can be a character or an integer number.

Use case: if (isalpha (CH)!=0)

3, Isascii function----Determine whether the ASCII code is located between 0~127, if it is, then return a non-0 value, if not, then return 0/

Function parameter: can be a character or an integer number.

Use case: if (ISASCII (CH)!=0)

4, Iscntrl function----Determine whether the control character (ASCII code is 0~31 and 0X7F//ASCII code 127), if it is, then return a non-0 value, if not, then return 0.

Function parameter: can be a character or an integer number.

Use case: if (Iscntrl (CH)!=0)

5, IsDigit function----Determine whether it is a numeric character (ASCII code is 48~57), if it is, then return a non-0 value, if not, then return 0

Function parameter: can be a character or an integer number.

Use case: if (isdigit (CH)!=0)

6, the Isgraph function---to judge in addition to the empty printable character (if a space, return 0). If yes, returns a non-0 value, or 0 if not.

Function parameter: can be a character or an integer number.

Use case: if (isgraph (CH)!=0)

7, Islower function---to determine whether it is a lowercase English letter. If so, returns a value other than 0, or 0 if not.

Function parameter: can be a character or an integer number.

Use case: if (islower (CH)!=0)

8, ispunct function---judge whether it is punctuation. If so, returns a value other than 0, or 0 if not.

Function parameter: can be a character or an integer number.

Use case: if (ispunct (CH)!=0)

9. The Isprint function---determine printable characters including spaces. If so, returns a value other than 0, or 0 if not.

Function parameter: can be a character or an integer number.

Use case: if (isprint (CH)!=0)

10. The Isspace function---determine if it is a blank character. If so, returns a value other than 0, or 0 if not.

Function parameter: can be a character or an integer number.

Use case: if (isspace (CH)!=0)

11. The Isxdigit function---determine if it is a hexadecimal character (emphasis). If so, returns a value other than 0, or 0 if not.

Function parameter: can be a character or an integer number.

Use case: if (isxdigit (CH)!=0)

Character Conversion functions

1. The ToLower function---converts uppercase letters to lowercase English letters. If CH is an uppercase English letter, the lowercase English letter is returned, and if not, the original character is returned.

Function parameter: can be a character or an integer number.

Use case: ToLower (CH);

2. The ToUpper function---Converts lowercase english letters to uppercase English letters. If CH is a lowercase English letter, the uppercase English letter is returned, and if not, the original character is returned.

Function parameter: can be a character or an integer number.

Use case: ToUpper (CH);

3. The TOASCII function---Converts the character to the corresponding ASCII code, and the digits outside the lower seven bits will be cleared

Function arguments: Characters

Use case: Toascii (CH); (only a single character, if it is a string, returns the ASCII code of the first character)

Ctype.h Library functions----character manipulation functions