23 Strings library [strings]

23.5 Null-terminated sequence utilities [c.strings]

23.5.1 Header <cctype> synopsis [cctype.syn]

namespace std { int isalnum(int c); int isalpha(int c); int isblank(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); }
The contents and meaning of the header <cctype> are the same as the C standard library header <ctype.h>.
See also: ISO/IEC 9899:2018, 7.4