Format
#include <ctype.h>
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);
General description
The functions listed in the previous section, which are all declared
in ctype.h, test a given integer value. The valid integer values for c are
those representable as an unsigned char or EOF.
Here are descriptions of each function in this group.
- isalnum()
- Test for an upper- or lowercase letter, or a decimal digit,
as defined by code page IBM-1047.
- isalpha()
- Test for an alphabetic character, as defined by code page IBM-1047.
- isblank()
- Test for a blank character, as defined by code page IBM-1047.
- iscntrl()
- Test for any control character, as defined by code page IBM-1047.
- isdigit()
- Test for a decimal digit, as defined by code page IBM-1047.
- isgraph()
- Test for a printable character excluding space, as defined by
code page IBM-1047.
- islower()
- Test for a lowercase character, as defined by code page IBM-1047.
- isprint()
- Test for a printable character including space, as defined by
code page IBM-1047.
- ispunct()
- Test for any non-alphanumeric printable character, excluding
space, as defined by code page IBM-1047.
- isspace()
- Test for a white space character, as defined by code page IBM-1047.
- isupper()
- Test for an uppercase character, as defined by code page IBM-1047.
- isxdigit()
- Test for a hexadecimal digit, as defined by code page IBM-1047.
Returned value
If the integer satisfies the test condition, these functions return
nonzero.
If the integer does not satisfy the test condition, these functions
return 0.