Character Inbuilt Functions

Single character Functions

header file :ctype.h

1. isalpha() :

This function helps us to check whether a specified character is an alphabet or not.  (a to z or A to Z) 

return value: the function returns nonzero if character is an alphabet otherwise this will return  zero which will be equivalent to false.

 #include <stdio.h>
 #include<ctype.h>
int main()
{
   char ch;
   printf("Enter any character ");
   scanf("%c",&ch);
   if(isalpha(ch))
   printf("it is an alphabet");
   else
   printf("it is not an alphabet");
    return 0;
}

Output:

Enter any character d
it is an alphabet

Enter any character 5
it is not an alphabet

2. islower() :

This function helps us to check whether a specified character is a lower case letter (a to z) or not.

#include <stdio.h>
 #include<ctype.h>
int main()
{
   char ch;
   printf("Enter any character ");
   scanf("%c",&ch);
    if(islower(ch))
   printf("it is a lower case alphabet");
   else
   printf("it is not a lower case alphabet");
    return 0;
}

Output:

Enter any character d
it is a lower case alphabet

Enter any character E
it is not a lower case alphabet

3. isupper() :

This function helps us to check whether the specifiedcharacter is an uppercase letter (A to Z ) or not.

#include <stdio.h>
 #include<ctype.h>
int main()
{
   char ch;
   printf("Enter any character ");
   scanf("%c",&ch);
   if(isupper(ch))
   printf("it is an upper case alphabet");
   else
   printf("it is not an upper case alphabet");
    return 0;
}

Output:

Enter any character D
it is an upper case alphabet

Enter any character w
it is not an upper case alphabet

4. isdigit() :

This function help us to check whether character is a digit (0 to 9) or not

#include <stdio.h>
 #include<ctype.h>
int main()
{
   char ch;
   printf("Enter any character ");
   scanf("%c",&ch);
   if(isdigit(ch))
   printf("it is a digit");
   else
   printf("it is not a digit");
    return 0;
}

Output:

Enter any character 5
it is a digit

Enter any character d
it is not a digit

5. isalnum():

This function helps us to check whether the specificed character is an alphanumeric or not.

#include<stdio.h>
 #include<conio.h>
 #include<ctype.h>
 void main()
 {
   char ch;
   clrscr();
   printf("Enter any character ");
   scanf("%c",&ch);
   if(isalnum(ch))
   printf("it is an alpha numeric character");
   else
   printf("it is not an alpha numeric character");
   getch();
 }

6. isgraph() :

This function helps us to check whether the specified character is a graphics character or not.
for example :
* ‘\n’ ‘\t’ ‘\b’ etc are not graph character.
* a b c are all graph character  

#include<stdio.h>
 #include<conio.h>
 #include<ctype.h>
 void main()
 {
   //char ch='a';
   char ch='\t';
   clrscr();
   if(isgraph(ch))
   printf("it is a graphical character");
   else
   printf("it is not a graphical character");
   getch();
 }