ctype.h

< ctype.h >

Judge function

isalnum

Check if character is alphanumeric (function )
判断是不是字母或者数字

isalpha

Check if character is alphabetic (function )
判断是否是字母

isblank

Check if character is blank (function )
判断是否是空白字符

iscntrl

Check if character is a control character (function )
判断是否是控制字符

isdigit

Check if character is decimal digit (function )
判断是否是数字

isgraph

Check if character has graphical representation (function )
除空格以外的任意可打印字符

islower

Check if character is lowercase letter (function )
判断是否是小写字母

isprint

Check if character is printable (function )
判断是否是可打印字符

ispunct

Check if character is a punctuation character (function )
判断是否是标点

isspace

Check if character is a white-space (function )
 判断是空白字符

isupper

Check if character is uppercase letter (function )
判断是否是大写字母

isxdigit

Check if character is hexadecimal digit (function )
判断是十六进制数字

Character conversion functions

Two functions that convert between letter cases:

tolower

 Convert uppercase letter to lowercase (function )
 变成小写

toupper

Convert lowercase letter to uppercase (function )
变成大写