Character functions in C Language | isalpha(), isdigit(), isalnum(), ispunct(), isspace(), isupper(), islower(), toupper(), tolower()

Character functions in C Language | isalpha(), isdigit(), isalnum(), ispunct(), isspace(), isupper(), islower(), toupper(), tolower()

Character functions need ctype.h  header file to be included in the pgoram. Different character functions provided by C Language are:

– isalpha()
– isdigit()
– isalnum()
– ispunct()
– isspace()
– isupper()
– islower()
– toupper()
– tolower()

1 isalpha() function in C Language:  

This function is used to check whether a character variable/constant contains alphabet or not. If it contains an alphabet it will return a non zero value.
Syntax:
isalpha(var_name);
var_name specifies character variable or character constant which want to check for whether it contains an alphabet or not.

2 isdigit() function in C Language:

This function is used to check whether the character variable /constant contains digit or not. If it contains a digit it will return a non zero value.
Syntax :
isdigit(var_name);
var_name specifies character variable or character constant which want to check for whether it contains a digit or not.

3 isalnum() function in C Language:

This function is used to check whether the /constant contains alphabet or digit. If it contains an alphabet or digit it will return a non zero value.
Syntax :
isalnum(var_name);
var_name specifies character variable or character constant which want to check for whether it contains an alphabet or a digit.

4. ispunct() function in C Language: 

This function is used to check whether a character variable /constant contains punctuator or not. Punctuators include comma, semicolon etc. If it contains a punctuator, it will return a non zero value.
Syntax:
ispunct(var_name);
var_name specifies character variable or character constant which want to check for whether it contains a punctuator or not.

5. isspace() function in C Language:

This function is used to check whether the character variable /constant contains blank space or not.  If it contains a blank space, it will return a non zero value.
Syntax :
isspace(var_name);
var_name specifies character variable or character constant which want to check for whether it contains a blank space or not.

Program to demonstrate the use of character() functions.

#include<ctype.h>
#include<stdio.h>
int main()
{
  char ch;
  printf("\nEnter any character=");
  ch=getche();
  if(isalpha(ch))
    printf("\nYou typed an alphabet");
  if(isdigit(ch))
    printf("\nYou typed a digit");
  if(isalnum(ch))
    printf("\nYou typed an alphabet or digit");
  if(ispunct(ch))
    printf("\nYou typed a punctuator");
  if(isspace(ch))
    printf("\nYou typed a space");
return 0;
}

Output

Enter any character= <blank Space>
You typed a space

6 isupper() function in C Language: 

This function is used to check whether the character variable /constant contains uppercase alphabet or not.  If it contains an uppercase alphabet, it will return a non zero value.
Syntax :
isupper(var_name);
var_name specifies character variable or character constant which want to check for whether it contains an uppercase alphabet or not.

7. islower() function in C Language:

This function is used to check whether the character variable /constant contains lowercase alphabet or not.  If it contains a lowercase alphabet, it will return a non-zero value.
Syntax :
islower(var_name);
var_name specifies character variable or character constant which want to check for whether it contains a lowercase alphabet or not.

Program to demonstrate the use of isupper() and islower() functions.

#include<ctype.h>
#include<stdio.h>
int main()
{
  char ch;
  printf("\nEnter an alphabet=");
  ch=getche();
  if(isupper(ch))
   printf("\nYou typed an upper case alphabet");
  if(islower(ch))
    printf("\nYou typed a lower case alphabet");
  return(0);
}

Output

Enter an alphabet= a
You typed a lower case alphabet

 8. toupper() function in C Language:  

This function is used to convert a lowercase character variable or character constant into uppercase alphabet.
Syntax :
toupper(var_name);
var_name specifies character variable or character constant which want to convert into uppercase.

9. tolower() function in C Language: 

This function is used to convert an uppercase character variable or character constant into lowercase alphabet.
Syntax :
tolower(var_name);
var_name specifies character variable or character constant which want to convert into lowercase.
Program to demonstrate the use of toupper() and tolower() function.
#include<ctype.h>
#include<conio.h>
#include<stdio.h>
int main()
{
  char ch;
  printf("\nEnter an alphabet=");
  ch=getche();
  ch=toupper(ch);
  printf("\nAlphabet in uppercase=%c",ch);
  ch=tolower(ch);
  printf("\nAlphabet in lowercase=%c",ch);
  return(0);
}

Output

Enter an alphabet= a
Alphabet in uppercase=A
Alphabet in lowercase=a

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Lesson tags: character formatting functions in c, character functions in c, Character functions in C Language, check whether a character is capital, check whether a character is digit, passing character variable as function argument
Back to: C Programming Language
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