<ctype.h>        -        Character handling

The header contains functions for testing and converting characters. In the following list, the declaration of each function is followed by a description of the value returned by each function. Note - a return value of !=0 (non-zero) implies true when used in a conditional statement.

1	int isalnum(int c);	!=0 if c is an alphanumeric character in range 'A'-'Z', 'a'-'z', '0'-'9'
2	int isalpha(int c);	!=0 if c is an alphabetic character is range 'A'-'Z', 'a'-'z'
3	int iscntrl(int c);	!=0 if c is a control character in range 0x0-0x1F or 0x7F
4	int isdigit(int c);	!=0 if c is a digit in range '0'-'9'
5	int isgraph(int c);	!=0 if c is a printable character (excluding space) in range 0x21-0x7E
6	int islower(int c);	!=0 if c is lower case letter in range 'a'-'z'
7	int isprint(int c);	!=0 if c is a printable character in range 0x20-0x7E
8	int ispunct(int c);	!=0 if c is a punctuation character in range 0x21-0x2F, 0x3A-0X40, 0X5B-0X60, 0X7B-0X7E
9	int isspace(int c);	!=0 if c is a white space character in range 0x9-0xD or 0x20
10	int isupper(int c);	!=0 if c is upper case letter in range 'A'-'Z'
11	int isxdigit(int c);	!=0 if c is a hexadecimal digit in range '0'-'9', 'A'-'F', 'a'-'f'
12	int tolower(int c);	return lower case value of character c in range 'a'-'z'
13	int toupper(int c);	return upper case value of character c in range 'A'-'Z'

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