C/ctype.h/isalpha

int isalpha(int ch)

<source lang="cpp">

//Declaration: int isalpha(int ch); //Return: returns nonzero if ch is a letter or zero if not.

 #include <ctype.h>
 #include <stdio.h>
 int main(void)
 {
   char ch;
   for(;;) {
      ch = getchar();
      if(ch == ".") {
         break;
      }
      if(isalpha(ch)) {
         printf("%c is a letter\n", ch);
      }
   }
   return 0;
 }
        

/* a a is a letter a a is a letter d d is a letter .

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      </source>