+.I TERM
+Denotes your terminal type.
+Each terminal type is distinct, though many are similar.
+.TP 5
+.I TERMCAP
+may denote the location of a termcap database.
+If it is not an absolute pathname, e.g., begins with a \*(``/\*('',
+\fB@TSET@\fP removes the variable from the environment before looking
+for the terminal description.
+.SH FILES
+.TP
+.I /etc/ttys
+system port name to terminal type mapping database (BSD versions only).
+.TP
+.I \*d
+compiled terminal description database directory
+.SH PORTABILITY
+Neither IEEE Std 1003.1/The Open Group Base Specifications Issue 7
+(POSIX.1-2008) nor
+X/Open Curses Issue 7 documents \fB@TSET@\fP or \fB@RESET@\fP.
+.PP
+The AT&T \fBtput\fP utility (AIX, HP-UX, Solaris)
+incorporated the terminal-mode manipulation as well as termcap-based features
+such as resetting tabstops from \fBtset\fP in BSD (4.1c),
+presumably with the intention of making \fBtset\fP obsolete.
+However, each of those systems still provides \fBtset\fP.
+In fact, the commonly-used \fBreset\fP utility
+is always an alias for \fBtset\fP.
+.PP
+The \fB\%@TSET@\fP utility provides backward compatibility with BSD
+environments;
+under most modern Unices,
+\fI\%/etc/inittab\fP and \fBgetty\fP(1) can set \fITERM\fP appropriately
+for each dial-up line,
+obviating what was \fB\%@TSET@\fP's most important use.
+This implementation behaves like 4.4BSD \fBtset\fP,
+with a few exceptions we shall consider now.
+.PP
+A few options are different
+because the \fI\%TERMCAP\fP variable
+is no longer supported under terminfo-based \fI\%ncurses\fP:
+.bP
+The \fB\-S\fP option of BSD \fBtset\fP no longer works;
+it prints an error message to the standard error and dies.
+.bP
+The \fB\-s\fP option only sets \fITERM\fP,
+not \fI\%TERMCAP\fP.
+.PP
+There was an undocumented 4.4BSD feature
+that invoking \fBtset\fP via a link named
+\*(``TSET\*('' (or via any other name beginning with an upper-case letter)
+set the terminal to use upper-case only.
+This feature has been omitted.
+.PP
+The \fB\-A\fP, \fB\-E\fP, \fB\-h\fP, \fB\-u\fP and \fB\-v\fP
+options were deleted from the \fB@TSET@\fP
+utility in 4.4BSD.
+None of them were documented in 4.3BSD and all are
+of limited utility at best.
+The \fB\-a\fP, \fB\-d\fP, and \fB\-p\fP options are similarly
+not documented or useful, but were retained as they appear to be in
+widespread use.
+It is strongly recommended that any usage of these
+three options be changed to use the \fB\-m\fP option instead.
+The \fB\-a\fP, \fB\-d\fP, and \fB\-p\fP options
+are therefore omitted from the usage summary above.
+.PP
+Very old systems, e.g., 3BSD, used a different terminal driver which
+was replaced in 4BSD in the early 1980s.
+To accommodate these older systems, the 4BSD \fB@TSET@\fP provided a
+\fB\-n\fP option to specify that the new terminal driver should be used.
+This implementation does not provide that choice.
+.PP
+It is still permissible to specify the \fB\-e\fP, \fB\-i\fP,
+and \fB\-k\fP options without arguments,
+although it is strongly recommended that such usage be fixed to
+explicitly specify the character.
+.PP
+As of 4.4BSD,
+executing \fB@TSET@\fP as \fB@RESET@\fP no longer implies the \fB\-Q\fP option.
+Also, the interaction between the \- option and the \fIterminal\fP
+argument in some historic implementations of \fB@TSET@\fP has been removed.
+.PP
+The \fB\-c\fP and \fB\-w\fP options are not found in earlier implementations.
+However, a different window size-change feature was provided in 4.4BSD.
+.bP
+In 4.4BSD, \fBtset\fP uses the window size from the termcap description
+to set the window size if \fBtset\fP is not able to obtain the window
+size from the operating system.
+.bP
+In \fI\%ncurses\fP, \fB@TSET@\fP obtains the window size using
+\fBsetupterm\fP, which may be from
+the operating system,
+the \fILINES\fP and \fICOLUMNS\fP environment variables or
+the terminal description.
+.PP
+Obtaining the window size from the terminal description is common to
+both implementations, but considered obsolescent.
+Its only practical use is for hardware terminals.
+Generally speaking, a window size would be unset only if there were
+some problem obtaining the value from the operating system
+(and \fBsetupterm\fP would still fail).
+For that reason,
+the \fILINES\fP and \fI\%COLUMNS\fP environment variables
+may be useful for working around window-size problems.
+Those have the drawback that if the window is resized,
+those variables must be recomputed and reassigned.
+To do this more easily, use the \fBresize\fP(1) program.
+.SH HISTORY
+A \fB\%reset\fP command written by Kurt Shoens appeared in 1BSD
+(March 1978).
+.\" https://minnie.tuhs.org/cgi-bin/utree.pl?file=1BSD/s6/reset.c
+It set the \fIerase\fP and \fIkill\fP characters
+to \fB\*^H\fP (backspace) and \fB@\fP respectively.
+Mark Horton improved this \fB\%reset\fP in 3BSD
+(October 1979),
+adding \fIintr\fP,
+\fIquit\fP,
+\fIstart\fP/\fIstop\fP,
+and \fIeof\fP
+characters as well as changing the program to avoid modifying any user
+settings.
+.\" https://minnie.tuhs.org/cgi-bin/utree.pl?file=3BSD/usr/src/cmd/\
+.\" reset.c
+That version of \fB\%reset\fP did not use \fI\%termcap\fP.
+.PP
+Eric Allman wrote a distinct \fBtset\fP command for 1BSD,
+using a forerunner of \fI\%termcap\fP called \fI\%ttycap\fP.
+.\" https://minnie.tuhs.org/cgi-bin/utree.pl?file=1BSD/s6/tset.c
+.\" https://minnie.tuhs.org/cgi-bin/utree.pl?file=1BSD/man7/ttycap.7
+Allman's comments in the source code indicate
+that he began work in October 1977,
+continuing development over the next few years.
+By late 1979,
+it had migrated to \fI\%termcap\fP and handled the \fI\%TERMCAP\fP
+variable.
+.\" https://minnie.tuhs.org/cgi-bin/utree.pl?file=3BSD/usr/src/cmd/\
+.\" tset/tset.c
+Later comments indicate that \fBtset\fP was modified in September 1980
+to use logic copied from the 3BSD \*(``reset\*('' program when it was
+invoked as \fB\%reset\fP.
+.\" https://minnie.tuhs.org/cgi-bin/utree.pl?file=2.9BSD/usr/src/ucb/\
+.\" tset/tset.c
+This version appeared in 4.1cBSD, \" and backported to 2.9BSD
+late in 1982.
+Other developers such as Keith Bostic and Jim Bloom continued to modify
+\fBtset\fP until 4.4BSD was released in 1993.
+.PP
+The \fI\%ncurses\fP implementation was lightly adapted from the 4.4BSD
+sources to use the \fI\%terminfo\fP API by Eric S.\& Raymond
+<esr@snark.thyrsus.com>.