---------------------------------------------------------

check whether a character is alphabet or not

 check alphabets using ASCII value

#include <stdio.h>

int main()
{
    char ch;
   

    printf("Enter any character: ");
    scanf("%c", &ch);
   

    if((ch >= 'a' && ch <= 'z') || (ch >= 'A' && ch <= 'Z'))
    {
        printf("Character is an ALPHABET.");
    }
    else
    {
        printf("Character is NOT ALPHABET.");
    }

    return 0;
}

a character is alphabet or not

#include <stdio.h>

int main()
{
    char ch;

    printf("Enter any character: ");
    scanf("%c", &ch);


    if((ch >= 97 && ch <= 122) || (ch >= 65 && ch <= 90))
    {
        printf("Character is an ALPHABET.");
    }
    else
    {
        printf("Character is NOT ALPHABET.");
    }

    return 0;
}

-----------------------------------------------------------

simpal logioc

#include <stdio.h>

int main()
{
    char ch;

    printf("Enter any character: ");
    scanf("%c", &ch);


    if(ch=isalpha(ch))
    {
        printf("Character is an ALPHABET.");
    }
    else
    {
        printf("Character is NOT ALPHABET.");
    }

    return 0;
}