#Character sets G0 and G1
9 messages in this thread
Some of the other computers I log into from my Rainbow send escape
sequences that change my character set(s). (For example, when I log into a
Vax running VMS and use the MAIL utility. I don't know why, but MAIL sends
the sequence ESC ( 0 when it starts up.) I finally figured out how to get
back to alphabetic characters when it throws me into illegible "special &
line-drawing characters," by going into Set-Up and toggling the US/UK
setting twice.
But I'm still baffled by one thing. ESC ( 0 only sends me into special
characters sometimes. As near as I can tell from experiments and the back
of my "Owner's Manual," there are two character sets, G0 and G1. ESC ( 0
sets G0 to "special characters," and ESC ) 0 sets G1 to "special
characters." The only way I can tell whether at any given time I am using
G0 or G1 is to send ESC ( 0 or ESC ) 0 to the screen and see what happens.
When ESC ( 0 throws me into "special characters," ESC ) 0 does not, and I
deduce that I am using the G0 character set. Conversely, when ESC ) 0
throws me into "special characters," ESC ( 0 does not, and I deduce that I
am using the G1 set.
Furthermore, it seems to switch between G0 and G1 at random, and I can't
find what causes it or how to switch deliberately between the two.
Does anyone know the answer? Has anyone run across the problem and been as
baffled as I am?
Maybe the preceding message should be in the "Hardware" section — I wasn't
sure
Brian,
The Rainbow's method of selecting character sets entirely duplicates
the use of character sets by DEC's VT100 terminal. I would imagine that it
is rooted in history and that DEC is stuck with the system because it was
developed years ago.
Anyway, the Rainbow does have two main character sets, called G0 and
G1, and two "alternate" character sets, called G2 and G3, but you can't
change G2 and G3; "they" are the default character set from set-up, meaning
either the U.S. character set with a number sign above the 3 or the U.K.
character set with a pound sign there. (The Brits get to keep our dollar
sign above the 4.)
You can define G0 to be the U.K. character set by sending ESC (A, the
U.S. character set with ESC (B or the line drawing set with ESC(0.
Similarly, you select G1 with ESC )A, ESC )B or ESC )0.
Now, what I think you wanted to know: You can change from G0 to G1 by
sending control-N (ASCII 14) to the screen. You can change back from G1 to
G0 again by sending control-O (ASCII 15) to the screen.
You can also select a single character from G2 by sending ESC N or the
ASCII character 142 to the screen, and a single character from G3 by
sending ESC O (the letter, not the number) or the ASCII character 143.
Since G2 and G3 are just the set-up character sets, this isn't particularly
useful.
I would guess that the VAXen that your computer talks to are programmed
to keep graphics in either G0 or G1 and ASCII in the other, so they can use
control-N and control-O to shift back and forth.
— Carl
Carl,
Thanks for the help! Control-N (ASCII 14) does indeed change to G1, and
control-O (ASCII 15) changes to G0. (I also found while testing what
control-N does when typed at the keyboard: echoes everything on the
printer!)
I guess what I really need is a VT100 manual. The relevant section of
the Rainbow owners manual is certainly garbled.
— BFT
Brian,
I do find the VT100 manual — well, actually VT102 — pretty convenient
for finding these things. I'm not even sure of what you have in a Rainbow
owners manual, because my owners manual told me absolutely nothing.
Anyway, my VT102 manual is DEC publication no. EK-VT102-UG-003, which
may help you to order one, hoping that they're still in print.
— Carl
Carl: If Digital is still making VT100's they must still print manuals for
them. I'll see what I can find.
My Rainbow Owner's Manual is "part no." EK-R100E-OM-002, and I learned what
I knew before your note from Appendix H, "Rainbow Control Functions (Escape
Sequences)." It has some curious omissions, such as referring to G0 and G1
character sets without telling what they are or how to use them. It does
list quite a few escape sequences, but though it claims I should really
only use the ANSI sequences, it doesn't distinguish
clearly between ANSI and VT52 sequences, and some of the pages seem to be
in the wrong order.
Brian
Brian,
Digital hasn't made VT100s for about 8 years now.
-Bill
VT100's are obsolote but the VT200 and VT300 series terminals are supersets
of VT100 functions. The character set switching is all according to
appropriate ANSI standards – I will look it up at work.
Tim
Tim,
Yes, I know. Don't go to a lot of trouble though because I don't think
this is an open question. I was just responding to a comment that started,
"If Digital still makes VT100s, then…" and the comment about
character-set switching was, I think, a comment on the lack of specificity
in a Rainbow manual, not an actual technical question.
-Bill