A Little C Primer/C Character Class Test Library

These functions perform various tests on characters. They require the declaration: #include &lt;ctype.h&gt; The character is represented as an "int" and the functions return an "int". They return 0 if the test is false and non-0 if the test is true:

isalnum( c )    Character is alpha or digit. isalpha( c )    Character is alpha. iscntrl( c )    Character is control character. isdigit( c )    Character is decimal digit. isgraph( c )    Character is printing character (except space). islower( c )    Character is lower-case. isprint( c )    Character is printing character (including space). ispunct( c )    Character is printing character but not space/alpha-digit. isspace( c )    Character is space, FF, LF, CR, HT, VT. isupper( c )    Character is upper-case. isxdigit( c )   Character is hex digit. The library also contains two conversion functions that also accept and return an "int": tolower( c )   Convert to lower case. toupper( c )   Convert to upper case.