Re: Control characters

From: John Cowan (
Date: Thu Jul 06 2000 - 14:06:23 EDT

On Wed, 5 Jul 2000, john wrote:

> > IIRC, the Model 37 Teletype interpreted 0A as a newline function,
> Also models 33 and 38, which also interpreted x0D as carriage return.

Definitely not true of the model 33; it interpreted 0A as a line-feed,
and if it received one not preceded by 0D
                                          it would do this.
(Hopefully, you are all reading this email with a fixed-width font as
God intended.)

> > so ASCII allowed 0A to be interpreted as either LF or NL.
> That's non sequitur, but folks are like that.

How so? The LF behavior is different from the NL behavior.

> > DEC OSes notoriously distorted or misused the control characters, thus
> > ^U = NAK was used to kill an input line instead of ^X = cancel.
> Since some of these editing commands were actually
> merely echoed back from the main processor to the comm control
> unit through which the terminal was connected,

Definitely not true of any DEC OS; control characters were echoed as ^A, ^B,

> there was some
> fogging over of the concepts of source and destination. The comm
> controller would buffer up what was typed until it got a CR (0x0D)
> and so these editing controls were actually commands to that comm
> controller to clear its buffer.

Again, not true of any DEC OS; characters were interpreted one by one
and selectively echoed by the CPU only.
There were no buffering serial-line controllers for the PDP-8, and they
weren't introduced for the PDP-11 until later -- and even then, the typical
mode was to stop buffering on *any* control character.

John Cowan                         
	"You need a change: try Canada"  "You need a change: try China"
		--fortune cookies opened by a couple that I know

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