document distributed with 4.1BSD

SCCS-vsn: old/roff/USD.doc/troff.tutorial/tt05 4.1

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+.\"    @(#)tt05        4.1 (Berkeley) %G%
+.\"
+.NH
+Tabs
+.PP
+Tabs
+(the \s8ASCII\s0 `horizontal tab' character)
+can be used to produce output in columns,
+or to set the horizontal position of output.
+Typically
+tabs are used only in unfilled text.
+Tab stops are set by default every half inch from the
+current indent,
+but
+can be changed by the
+.BD .ta
+command.
+To set stops every inch, for example,
+.P1
+^ta 1i 2i 3i 4i 5i 6i
+.P2
+.PP
+Unfortunately the stops are left-justified only
+(as on a typewriter),
+so lining up columns of right-justified numbers can be painful.
+If you have many numbers,
+or if you need more complicated table layout,
+.ul
+don't
+use
+.UL troff 
+directly;
+use the
+.UL tbl
+program described in [3].
+.PP
+For a handful of numeric columns, you can do it this way:
+Precede every number by enough blanks to make it line up
+when typed.
+.P1
+^nf
+^ta 1i 2i 3i
+\0\01\0\fItab\fR\0\0\02\0\fItab\fR\0\0\03
+\040\0\fItab\fR\0\050\0\fItab\fR\0\060
+700\0\fItab\fR\0800\0\fItab\fR\0900
+^fi
+.P2
+Then change each leading blank into the string
+.BD \e0 .
+This is a character that does not print, but that has
+the same width as a digit.
+When printed, this will produce
+.P1
+.ta 1i 2i 3i
+\0\01  \0\02   \0\03
+\040   \050    \060
+700    800     900
+.P2
+.PP
+It is also possible to fill up tabbed-over space with
+some character other than blanks by setting the `tab replacement character'
+with the
+.BD .tc
+command:
+.P1
+^ta 1.5i 2.5i
+^tc \e(ru      (\e(ru is "\(ru")
+Name \fItab\fR Age \fItab\fR 
+.P2
+produces
+.P1 3
+.ta 1.5i 2.5i
+.tc \(ru
+Name    Age    
+.tc
+.P2
+To reset the tab replacement character to a blank, use
+.BD .tc
+with no argument.
+(Lines can also be drawn with the
+.BD \el
+command, described in Section 6.)
+.PP
+.UL troff
+also provides a very general mechanism called `fields'
+for setting up complicated columns.
+(This is used by
+.UL tbl ).
+We will not go into it in this paper.