 until the byte is ready,
		using YIELD. parameter: stream number in x, returns
		the read byte in a
$e7fa	Fputc	Write a byte on a stream, waiting until it can be delivered
		parameter: stream number in x, data byte in a
$e7f7	Getc	same as Fgetc, for STDIN
$e7f4	Putc	same as Fputc, for STDOUT
$e7f1	Txtout	Write a null terminated string up to 254 byte to STDOUT
		parameter: a/y=address of string (a=lowbyte, y=highbyte)
$e7ee	Hexout	Write a byte to STDOUT in hex. parameter: byte in a
$e7eb	Crlfout	Write carri