# putch - write a character c to file fd.
# NOTE AOS/RDOS DIFFERENCE BELOW !!
include ratdef
   subroutine putch (c, fd)
   integer c, fd
   include channel
   
   if (0 <= fd & fd <= MAXCHNL & channel(fd) ^= ERR) {
      if (md(fd) ^= WRITE) {	# fix up pointers if last operation not WRITE
	 md(fd) = WRITE; ic(fd) = 1; nc(fd) = 0
	 }
      if (c == NEWLINE) {
	 # change NEWLINE to CR and flush the buffer if RDOS
	 # insert NEWLINE and flush buffer if AOS
#	  byte(linebuf(1,fd),ic(fd)) = CR	#RDOS
	  byte(linebuf(1,fd),ic(fd)) = NEWLINE	#AOS
	  ic(fd) = ic(fd) + 1
	 call flush (fd)
	 }
      else {
	 byte(linebuf(1,fd),ic(fd)) = c
	 ic(fd) = ic(fd) + 1
	 if (ic(fd) > MAXLINE | c == CR) {	# this causes sequential write
	    call wrseq (fd, linebuf(1,fd), ic(fd), ier)
	    call chkio (fd, ier)
	    ic(fd) = 1
	    }
	 else if (c == FF | c == NULL)		# these cause line write
	    call flush (fd)
	 }
      }
   return
   end