Bug or undocumented feature?

[Willem Grooters]

Just a reminder....

A collegue of mine ran into the following issue using DCL using a terminal emulator:
He typed:

$ Saerch file "123456789"

Saw his mistake, reversed using the left-arrow key to change "ae" to "ea" - DELETE did work but hitting any 'normal' key DIDN'T WORK

After using the right-arrow key, passed character, hit DELETE and was removed. Back to front using left-arrow key to "ae" - and now he could indeed change it.

I tried this using the DOS telnet from my XP machine and the same behaviour. On my Alpha, using DECTerm (I have no plain VT..) the same behaviour.

Probably normal, but it can be quite a surprise...

Willem

[Åge Rønning]

I found some old notes(from the early 90s) saying this is a documented restriction. Terminal-driver line editing does not allow insertion to the left of a tab. Seems like what you're seeing.

Havn't tried to find where it's documented.

\Aage

[John Gillings · Accepted solution]

See "OpenVMS I/O User's Reference Manual"

5.2.1.1 Command-Line Editing and Command Recall
...
When you use the terminal driver's editing functions, the following restrictions result:

You cannot move the cursor to a previous line after a line wrap.

You cannot insert a character if the insertion would force a line wrap or if a tab follows the current cursor position.

You cannot delete a word at the beginning of a line after a line wrap.

You cannot assign the line editing function to other keys.

...

[Bob Blunt]

Willem,

I didn't see anything mentioned about the line wrapping, was that the case or was your collegue's input right at the end of the line length for the terminal in question? Is the terminal set for insert or overstrike? The pertinent settings would at least be "Line Editing" and "Overstrike editing" (or "Insert editing"). The "type" terminal setting for the emulator may also affect how you can edit the line. Need to check to see if the terminal type is either one of the hardcopy terminals or a much more primitive video terminal, too.

[Bojan Nemec]

Willem,

The same is on a "real" VT420 and VT510. Seems that DCL cant insert a character before a character. When in overstrike mode, characters can be modified.

Bojan

[Willem Grooters]

As I started - just a reminder, John's remark - and some good-sense-thinking - made me understand the behaviour.