Previous Section 2.1 assert.h |
| Table of Contents | Index | |
Next Section
2.3 errno.h |
The ctype header is used for testing and converting characters. A control character refers to a character that is not part of the normal printing set. In the ASCII character set, the control characters are the characters from 0 (NUL) through 0x1F (US), and the character 0x7F (DEL). Printable characters are those from 0x20 (space) to 0x7E (tilde).
Functions:
isalnum();
isalpha();
iscntrl();
isdigit();
isgraph();
islower();
isprint();
ispunct();
isspace();
isupper();
isxdigit();
tolower();
toupper();
Declarations:
The is... functions test the given character and return a nonzero (true) result if it satisfies the following conditions. If not, then 0 (false) is returned.int isalnum(int
character);
character
int isalpha(int);
character
int iscntrl(int);
character
int isdigit(int);
character
int isgraph(int);
character
int islower(int);
character
int isprint(int);
character
int ispunct(int);
character
int isspace(int);
character
int isupper(int);
character
int isxdigit(int);
Conditions:
isalnum |
a letter (A to Z or a to z) or a digit (0 to 9) |
isalpha |
a letter (A to Z or a to z) |
iscntrl |
any control character (0x00 to 0x1F or 0x7F) |
isdigit |
a digit (0 to 9) |
isgraph |
any printing character except for the space character (0x21 to 0x7E) |
islower |
a lowercase letter (a to z) |
isprint |
any printing character (0x20 to 0x7E) |
ispunct |
any punctuation character (any printing character except for space character or isalnum) |
isspace |
a whitespace character (space, tab, carriage return, new line, vertical tab, or formfeed) |
isupper |
an uppercase letter (A to Z) |
isxdigit |
a hexadecimal digit (0 to 9, A to F, or a to f) |
Declarations:
The to... functions provide a means to convert a single character. If the character matches the appropriate condition, then it is converted. Otherwise the character is returned unchanged.int tolower(int
character);
character
int toupper(int);
Conditions:
tolower |
If the character is an uppercase character (A to Z), then it is converted to lowercase (a to z) |
toupper |
If the character is a lowercase character (a to z), then it is converted to uppercase (A to Z) |
#include<ctype.h>
#include<stdio.h>
#include<string.h>
int main(void)
{
int loop;
char string[]="THIS IS A TEST";
for(loop=0;loop<strlen(string);loop++)
string[loop]=tolower(string[loop]);
printf("%s\n",string);
return 0;
}
Previous Section 2.1 assert.h |
| Table of Contents | Index | |
Next Section
2.3 errno.h |