craig.umcp-cs@UDel-Relay@sri-unix (10/27/82)
From: Craig Stanfill <craig.umcp-cs@UDel-Relay>
You have complained that your version of the TEK-4025 firmware is too
slow to handle incoming cursor commands while you are typing. Is your
host echoing your typing? If the host echos text from the keyboard
inside of a cursor motion or other command the result will, of course,
be garbled.
By the way, I have a unix-to-tek synchronization filter; the TEK doesn't
know the x-on/x-off protocol, but there are ways of synchronizing
communication which partly make up for this problem.
The terminal is slow, but this is less of a problem than two misfeatures
in the firmware.
1. The screen may be divided into two regions, the Workspace and
the Monitor. The Workspace has cursor addressing and special
visual attributes; the Monitor has scrolling. Unfortunately,
whenever the cursor is in the Workspace, text goes directly
into the workspace, not the host. This makes the Workspace
useless for most interactive tasks - editing, for example.
It is possible for the Host to talk to the Workspace without
displaying a cursor, but a display without a cursor is
almost useless. The terminal is usable only because our
visual editor ('vi') is smart enough to use the limited number
of cursor motion commands which work in the monitor.
2. Visual attributes are done wrong. With most terminals,
the host sends a command which means 'display all following
text underlined', (or blinking, or reverse video, etc.).
With the TEK 4025, you send a code which gets inserted
in the screen, and means "underline from here to the next attribute
code, or the end of the line." A program which is written
assuming an interface similar to the 'normal' cannot be made
to work; if underlined text spans two lines, the text on the
second line will not be underlined. Programs which update
the screen become unworkable; old attribute codes interfere
with each other. Inserting a single underlined character in
the middle of the screen may cause the rest of the line
to become underlined. In fact, inserting a single underlined
character in the display is safe only if you have a
complete model of everything that has been done to the
screen. This problem is a result of hardware decisions,
but the firmware could have compensated for the hardware
design.
I would like to know exactly how tektronix came up with the interface
to this terminal. I tend to think they didn't do much homework.
They should have taken care not to write firmware which made their terminal
incompatable with most software.