Standard C++ Library Reference ISO/IEC (VERSION3)

The diagram tells you that the function isprint returns nonzero for space or for any
character for which the function isgraph returns nonzero. The function isgraph, in turn,
returns nonzero for any character for which either the function isalnum or the function
ispunct returns nonzero. The function isdigit, on the other hand, returns nonzero only for
the digits 0-9.
An implementation can define additional characters that return nonzero for some of these
functions. Any character set can contain additional characters that return nonzero for:
iscntrl (provided the characters cause isprint to return zero)●
ispunct (provided the characters cause isalnum to return zero)●
The diagram indicates with ++ those functions that can define additional characters in any
character set. Moreover, locales other than the "C" locale can define additional characters that
return nonzero for:
isalpha, isupper, and islower (provided the characters cause iscntrl,
isdigit, ispunct, and isspace to return zero)
●
isspace (provided the characters cause isprint to return zero)●
Note that an implementation can define locales other than the "C" locale in which a character
can cause isalpha (and hence isalnum) to return nonzero, yet still cause isupper and
islower to return zero.
int isalnum(int c);
int isalpha(int c);
int iscntrl(int c);
int isdigit(int c);
int isgraph(int c);
int islower(int c);
int isprint(int c);
int ispunct(int c);
int isspace(int c);
int isupper(int c);
int isxdigit(int c);
int tolower(int c);
int toupper(int c);
isalnum
int isalnum(int c);
The function returns nonzero if c is any of:
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