C/ctype.h/isprint

//Declaration:  int isprint(int ch); 
//Return:       returns nonzero if ch is a printable character, including a space; 
                otherwise zero is returned. 
   
  
  #include <ctype.h>
  #include <stdio.h>
  int main(void)
  {
    char ch;
    for(;;) {
      ch = getchar();
      if(isprint(ch)){
          printf("%c is printable\n",ch);
      }
      if(ch == "."){
          break;
      }
    }
    return 0;
  }
         
/*
a
a is printable
s
s is printable
d
d is printable
f
f is printable
.
. is printable
*/