CTYPE.H

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Introduction

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). www.ustudy.in

NAME

ctype.h - character types  

SYNOPSIS

#include <ctype.h>

 DESCRIPTION

• The header ctype.h in the ANSI C Standard Library for the C

programming language contains declarations for character

classification functions.

• Function prototypes must be provided for use with an ISO C

compiler. www.ustudy.in

isalnum NAME

isalnum - test for an alphanumeric character

 SYNOPSIS

#include <ctype.h>

int isalnum(int c);  

DESCRIPTION

• The isalnum() function tests whether c is a character of class alpha or digit in the program's

current locale, see the XBD specification, locale.

• In all cases c is an int, the value of which must be representable as an unsigned char or must

equal the value of the macro EOF. If the argument has any other value, the behavior is undefined.

 RETURN VALUE

• The isalnum() function returns non-zero if c is an alphanumeric character; otherwise it returns 0.

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Example#include<ctype.h> //isalnum() #include<stdio.h> //printf() void test_isalnum() {    int arr[]={'8',0xe1,'5','Z',0xfd};    int i = 0;    int size = 5;    for( i=0; i<size; i++)    {       int ret = isalnum(arr[i]); //call to the API with chars in arr[]       if( (!ret) != 0 )       {           printf(“ c is not alphanumeric", arr[i]);       }       else       {           printf(" %c is an alphanumeric ", arr[i]);       }    }   } Output a is an alphanumeric5 is an alphanumericZ is an alphanumeric

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isalphaNAME

isalpha - test for an alphabetic character  SYNOPSIS

#include <ctype.h> int isalpha(int c);

 DESCRIPTIONThe isalpha() function tests whether c is a character of class alpha in

the program's current locale, see the XBD specification,locale. In all cases c is an int, the value of which must be representable as an

unsigned char or must equal the value of the macro EOF. If the argument has any other value, the behavior is undefined.

 RETURN VALUEThe isalpha() function returns non-zero if c is an alphabetic character; otherwise it returns 0.

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Example#include<ctype.h> //isalpha() #include<stdio.h> //printf() void test_isalpha() {    int arr[]={'a',0xe1,'5','Z',0xfd};    int i = 0;    int size = 5;    for( i=0; i<size; i++)    {       int ret = isalpha(arr[i]); //call to the API with chars in arr[]       if( (!ret) != 0 )       {         printf(“c is not an alphabet", arr[i]);      }       else       {         printf(" %c is an alphabet", arr[i]);       }    }   } Output a is an alphabet 5 is not an alphabet Z is an alphabetwww.ustudy.in

isasciiNAME

isascii - test for a 7-bit US-ASCII character

SYNOPSIS#include <ctype.h> int isascii(int c);  

DESCRIPTION• The isascii() function tests whether c is a 7-bit US-ASCII character code.

The isascii() function is defined on all integer values.

RETURN VALUE• The isascii() function returns non-zero if c is a 7-bit US-ASCII character

code between 0 and octal 0177 inclusive; otherwise it returns 0.

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iscntrl NAME

iscntrl - test for a control character  

SYNOPSIS#include <ctype.h> int iscntrl(int c);

 DESCRIPTIONThe iscntrl() function tests whether c is a character of class cntrl in the

program's current locale, see the XBD specification,locale. In all cases c is a type int, the value of which must be a character representable

as an unsigned char or must equal the value of the macro EOF. If the argument has any other value, the behaviour is undefined.

 RETURN VALUEThe iscntrl() function returns non-zero if c is a control character; otherwise it

returns 0.

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isdigit NAME

isdigit - test for a decimal digit  

SYNOPSIS#include <ctype.h> int isdigit(int c);  

DESCRIPTIONThe isdigit() function tests whether c is a character of class digit in the

program's current locale, see the XBD specification, Locale . In all cases c is an int, the value of which must be a character

representable as an unsigned char or must equal the value of the macro EOF. If the argument has any other value, the behaviour is undefined.

 RETURN VALUEThe isdigit() function returns non-zero if c is a decimal digit; otherwise it

returns 0. www.ustudy.in

Example#include<ctype.h> //isdigit() #include<stdio.h> //printf() void test_isdigit() {    int arr[]={'8',0xe1,'5','Z',0xfd};    int i = 0;    int size = 5;    for( i=0; i<size; i++)    {      int ret = isdigit(arr[i]); //call to the API with chars in arr[]      if( (!ret) != 0 )      {          printf(" %c is not a digit", arr[i]);      }      else      {          printf(" %c is a digit", arr[i]);      }      } printf(" "); } Output 8 is a digit 5 is a digit Z is not a digit

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isxdigitNAME

isxdigit - test for a hexadecimal digit  SYNOPSIS

#include <ctype.h> int isxdigit(int c);

DESCRIPTION• The isxdigit() function tests whether c is a character of class xdigit in the

program's current locale, see the XBD specification, Locale . • In all cases c is an int, the value of which must be a character representable

as an unsigned char or must equal the value of the macro EOF. If the argument has any other value, the behavior is undefined.

 RETURN VALUE• The isxdigit() function returns non-zero if c is a hexadecimal digit;

otherwise it returns 0. www.ustudy.in

Example#include<ctype.h> //isxdigit() #include<stdio.h> //printf() int test_isxdigit() {    int arr[]={'F','a','M','9','2'};    int i = 0;    int size = 5;    for( i=0; i<size; i++)    {       int ret = isxdigit(arr[i]); //call to the API with chars in arr[]       if( (!ret) != 0 )       {           printf(" %c is not hex-digit ", arr[i]);       }       else       {           printf(" %c is hex-digit", arr[i]);       } } printf(" "); } Output F is hex-digit a is hex-digit M is not hex-digit 9 is hex-digit

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isgraphNAME

isgraph - test for a visible character

SYNOPSIS#include <ctype.h> int isgraph(int c);

DESCRIPTION The isgraph() function tests whether c is a character of class graph in the

program's current locale, see the XBD specification, Locale . In all cases c is an int, the value of which must be a character representable as

an unsigned char or must equal the value of the macro EOF. If the argument has any other value, the behaviour is undefined.

RETURN VALUE The isgraph() function returns non-zero if c is a character with a visible

representation; otherwise it returns 0.

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islowerNAMEislower - test for a lower-case letter  

SYNOPSIS#include <ctype.h> int islower(int c);  

DESCRIPTIONThe islower() function tests whether c is a character of class lower in the

program's current locale, see the XBD specification, Locale . In all cases c is an int, the value of which must be a character representable

as an unsigned char or must equal the value of the macro EOF. If the argument has any other value, the behaviour is undefined.

RETURN VALUEThe islower() function returns non-zero if c is a lower-case letter; otherwise

it returns 0. www.ustudy.in

Example#include<ctype.h> //islower() #include<stdio.h> //printf() int test_islower() {   int arr[]={0x0126,0xee,'r','9','g'};   int i = 0;   int size = 5;   for( i=0; i<size; i++)   {      int ret = islower(arr[i]); //call to the API with chars in the arr[]      if( (!ret) != 0 )      {          printf(" %c is not in lower-case ", arr[i]);      }      else      {          printf(" %c is in lower-case", arr[i]);      }   } printf(" "); } Output & is not in lower-case 9 is not in lower-case g is in lower-case

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isupper NAME

isupper - test for an upper-case letter

 SYNOPSIS#include <ctype.h> int isupper(int c);

 DESCRIPTION The isupper() function tests whether c is a character of class upper in the

program's current locale, see the XBD specification, Locale . In all cases c is an int, the value of which must be a character representable as

an unsigned char or must equal the value of the macro EOF. If the argument has any other value, the behaviour is undefined.

 RETURN VALUE The isupper() function returns non-zero if c is an upper-case letter; otherwise it

returns 0.

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Example#include<ctype.h> //isupper() #include<stdio.h> //printf() int test_isupper() { int arr[]={0x0126,'G','7','B',0x3041}; int i = 0; int size = 5; for( i=0; i<size; i++) {    int ret = isupper(arr[i]); //call to the API with chars in arr[]    if( (!ret) != 0 )    {         printf(" %c is not in upper-case ", arr[i]);    }    else    {         printf(" %c is in upper-case", arr[i]);    }    } printf(" "); } Output G is in upper-case 7 is not in upper-case A is in upper-case

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isprintNAME

isprint - test for a printing character

 SYNOPSIS#include <ctype.h> int isprint(int c);

 DESCRIPTION The isprint() function tests whether c is a character of class print in the

program's current locale, see the XBD specification, Locale . In all cases c is an int, the value of which must be a character representable

as an unsigned char or must equal the value of the macro EOF. If the argument has any other value, the behaviour is undefined.

 RETURN VALUE The isprint() function returns non-zero if c is a printing character; otherwise

it returns 0.

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ispunct NAME

ispunct - test for a punctuation character  SYNOPSIS

#include <ctype.h> int ispunct(int c);

DESCRIPTIONThe ispunct() function tests whether c is a character of class punct in the

program's current locale, see the XBD specification, Locale . In all cases c is an int, the value of which must be a character

representable as an unsigned char or must equal the value of the macro EOF. If the argument has any other value, the behavior is undefined.

 RETURN VALUEThe ispunct() function returns non-zero if c is a punctuation character;

otherwise it returns 0. www.ustudy.in

isspaceNAMEisspace - test for a white-space character  

SYNOPSIS#include <ctype.h> int isspace(int c);

DESCRIPTIONThe isspace() function tests whether c is a character of class space in the

program's current locale, see the XBD specification, Locale . In all cases c is an int, the value of which must be a character

representable as an unsigned char or must equal the value of the macro EOF. If the argument has any other value, the behaviour is undefined.

RETURN VALUEThe isspace() function returns non-zero if c is a white-space character;

otherwise it returns 0.

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toasciiNAMEtoascii - translate integer to a 7-bit ASCII character

 SYNOPSIS#include <ctype.h> int toascii(int c);  DESCRIPTION• The toascii() function converts its argument into a 7-bit ASCII

character.

 RETURN VALUE• The toascii() function returns the value (c & 0x7f).

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tolower NAME

tolower - transliterate upper-case characters to lower-case

 SYNOPSIS

#include <ctype.h>

int tolower(int c);

 DESCRIPTION

• The tolower() function has as a domain a type int, the value of which is representable as an unsigned

char or the value of EOF. If the argument has any other value, the behaviour is undefined.

• If the argument of tolower() represents an upper-case letter, and there exists a corresponding lower-

case letter (as defined by character type information in the program locale category LC_CTYPE), the

result is the corresponding lower-case letter. All other arguments in the domain are returned

unchanged.  

RETURN VALUE

• On successful completion, tolower() returns the lower-case letter corresponding to the argument

passed; otherwise it returns the argument unchanged.

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Example#include <stdio.h>#include<ctype.h> int main() { printf( "Lower case of A is %c\n", tolower('A')); printf( "Lower case of 9 is %c\n", tolower('9')); printf( "Lower case of g is %c\n", tolower('g')); return 0; }

Output:Lower case of A is a Lower case of 9 is 9 Lower case of g is g

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toupperNAME

toupper - transliterate lower-case characters to upper-case  

SYNOPSIS

#include <ctype.h>

int toupper(int c);  

DESCRIPTION

The toupper() function has as a domain a type int, the value of which is representable as an

unsigned char or the value of EOF. If the argument has any other value, the behavior is

undefined.

If the argument of toupper() represents a lower-case letter, and there exists a corresponding

upper-case letter (as defined by character type information in the program locale category

LC_CTYPE), the result is the corresponding upper-case letter. All other arguments in the domain

are returned unchanged.  

RETURN VALUE

On successful completion, toupper() returns the upper-case letter corresponding to the argument

passed. www.ustudy.in

Example#include <stdio.h>#include<ctype.h> int main() { printf( “Upper case of a is %c\n", toupper(‘a')); printf( " Upper case of 9 is %c\n", toupper('9')); printf( " Upper case of g is %c\n", toupper(‘G')); return 0; }

Output:

Upper case of a is AUpper case of 9 is 9 Upper case of G is G

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The End

Thank U

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