[TUHS] I swear! I rtfm'ed
Mary Ann Horton
mah at mhorton.net
Fri Jan 2 01:59:51 AEST 2015
The move was from termcap to terminfo. Termlib was the library for termcap.
There were two problems with termcap. One was that the two-character
name space was running out of room, and the codes were becoming less and
less mnemonic.
But the big motivator was performance. Reading in a termcap entry from
/etc/termcap was terribly slow. First you had to scan all the way
through the (ever-growing) termcap file to find the correct entry. Once
you had it, every tgetstr (etc) had to scan from the beginning of the
entry, so starting up a program like vi involved quadratic performance
(time grew as the square of the length of the termcap entry.) The VAX
11/780 was a 1 MIPS processor (about the same as a 1 MHz Pentium) and
was shared among dozens of timesharing users, and some of the other
machines of the day (750 and 730 Vaxen, PDP-11, etc.) were even slower.
It took forever to start up vi or more or any of the termcap-based
programs people were using a lot.
I wrote a paper about it for Usenix in 1982, but it seems to be lost to
Google. Here is a nice write-up Pavel Curtis posted about it with more
detail about the motivation:
http://www.informatica.co.cr/unix-source-code/research/1982/0711.html
Mary Ann
On 01/01/2015 07:03 AM, Johnny Billquist wrote:
> On 2015-01-01 02:29, Erik E. Fair wrote:
>> All those terminal quirks made writing termcap entries challenging
>> (I wrote a few), and made the comments in the termcap file interesting
>> reading for the frustration and cursing of terminal firmware authors.
>> All kinds of history of the evolution of terminals is captured therein.
>>
>> The removal of the ability to read the source is - IMHO - what
>> greatly impeded adoption of the AT&T "termlib" replacement for
>> termcap: they stopped distributing the terminal database source
>> (they distributed just the binary "compiled" versions), and made it
>> harder to write new entries.
>
> I was way to removed from the action to know, but why did people
> slowly move over to termlib? Was there really any advantages over
> termcap?
>
> Johnny
>
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