CR LF was: freebsd vs. netbsd
freebsd at edvax.de
Sat Jun 13 06:56:57 UTC 2020
On Fri, 12 Jun 2020 19:32:54 +0000, Montgomery-Smith, Stephen wrote:
> On 6/12/20 2:21 PM, Ottavio Caruso via freebsd-questions wrote:
> > On Fri, 12 Jun 2020 at 19:58, Kurt Hackenberg <kh at panix.com> wrote:
> >> On 2020-06-12 02:14, Polytropon wrote:
> >>>> But it's often done by redefining the ASCII characters carriage return
> >>>> and line feed. Originally they meant, respectively, move the print head
> >>>> to the left margin, and roll the paper up a line.
> >>> Erm... no. The carriage return returns the _carriage_ to the
> >>> first position (here: to the right), that's why it is called
> >>> carriage return and not print head return. :-)
> >>> On older electrical typewriters, you will see...
> >> Electric typewriters didn't use ASCII.
> > Maybe the OP meant teleprinters, which did indeed use 5-bit and 7-bit
> > ascii, still used today by hams in RTTY and other legacy digital
> > modes.
> I used to have a teletype. On these devices, the CR would cause the
> printer head to go to the left margin, and the LF would cause the page
> to move up one line.
> It always seemed to me to be a waste of bits. Why not have one ASCII
> code that did both? Then I found out why.
> One time, I decided to try a LF CR at the end of a line instead of CR
> LF. I found that the next character that was typed ended up in the
> middle of the page, not on the far left as it should have been. What I
> realized was that the CR takes time to complete, because it has to
> physically move the printer head to the left margin. The extra LF gave
> the printer the extra time it needed.
> So I don't know about typewriters, but teletypes definitely used CR and
> LF for two different purposes. And it really was necessary to have CR
> LF at the ends of the lines.
This was also true for teletypes with a fixed "type basket"
and a moving carriage. Additionally, teletype operation
guides encourage the use of CR LF as you described, and
state that multiple line vertical spacing is to be done
using CR LF LF LF LF as needed. That's why there are two
keys on the traditional TTY keyboard.
Happy FreeBSD user since 4.0
Andra moi ennepe, Mousa, ...
More information about the freebsd-questions