+</PRE><H2><a name="h2-HISTORY">HISTORY</a></H2><PRE>
+ A <STRONG>tabs</STRONG> utility appeared in PWB/Unix 1.0 (1977). A reduced version
+ shipped in Seventh Edition Unix (early 1979) and in 3BSD (later the
+ same year); it supported a "-n" option to set the first tab stop at the
+ left margin. That option is not specified by POSIX.
+
+ The PWB/Unix <STRONG>tabs</STRONG> utility returned in System III (1980), and used
+ built-in tables to support a half-dozen hardcopy terminal (printer)
+ types. It also had logic to support setting the left margin, as well
+ as a feature for copying the tab settings from a file.
+
+ Versions of the program in later releases of AT&T Unix, such as SVr4,
+ added support for the terminal database, but retained the tables to
+ support the printers. By this time, System V <STRONG>tput</STRONG> had incorporated the
+ tab stop initialization feature of BSD's <STRONG>tset</STRONG> from 1982, but employed
+ the <EM>terminfo</EM> database to do so.
+
+ The <STRONG>+m</STRONG> option was documented in the POSIX Base Specifications Issue 5
+ (Unix98, 1997), then omitted in Issue 6 (Unix03, 2004) without express
+ motivation, though an introductory comment "and optionally adjusts the
+ margin" remains, overlooked in the removal. The <STRONG>tabs</STRONG> utility
+ documented in Issues 6 and later has no mechanism for setting margins.
+ The <STRONG>+m</STRONG> option in <EM>ncurses</EM> <STRONG>tabs</STRONG> differs from the SVr4 feature by using
+ terminal capabilities rather than built-in tables.
+
+ POSIX documents no limit on the number of tab stops. Other
+ implementations impose one; the limit is 20 in PWB/Unix's <STRONG>tabs</STRONG> utility.
+ While some terminals may not accept an arbitrary number of tab stops,
+ <EM>ncurses</EM> <STRONG>tabs</STRONG> attempts to set tab stops up to the right margin if the
+ list thereof is sufficiently long.
+
+ The "Rationale" section of the Issue 6 <STRONG>tabs</STRONG> reference page details how
+ the committee considered redesigning the <STRONG>tabs</STRONG> and <STRONG>tput</STRONG> utilities,
+ without settling on an improved solution. It claims that
+
+ "no known historical version of <EM>tabs</EM> supports the capability of
+ setting arbitrary tab stops."
+
+ The feature described in subsection "Explicit Lists" above was
+ implemented in PWB/Unix, and permitted the setting of abitrary tab
+ stops nevertheless.