245 lines
6.5 KiB
Plaintext
245 lines
6.5 KiB
Plaintext
.\" This module is believed to contain source code proprietary to AT&T.
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.\" Use and redistribution is subject to the Berkeley Software License
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.\" Agreement and your Software Agreement with AT&T (Western Electric).
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.\"
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.\" @(#)tt02 8.1 (Berkeley) 6/8/93
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.\" Copyright (C) Caldera International Inc. 2001-2002. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions are
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.\" met:
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.\"
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.\" Redistributions of source code and documentation must retain the above
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.\" copyright notice, this list of conditions and the following
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.\" disclaimer.
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.\"
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.\" Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\"
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.\" This product includes software developed or owned by Caldera
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.\" International, Inc. Neither the name of Caldera International, Inc.
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.\" nor the names of other contributors may be used to endorse or promote
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.\" products derived from this software without specific prior written
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.\" permission.
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.\"
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.\" USE OF THE SOFTWARE PROVIDED FOR UNDER THIS LICENSE BY CALDERA
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.\" INTERNATIONAL, INC. AND CONTRIBUTORS ``AS IS'' AND ANY EXPRESS OR
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.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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.\" WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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.\" DISCLAIMED. IN NO EVENT SHALL CALDERA INTERNATIONAL, INC. BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT INCIDENTAL, SPECIAL, EXEMPLARY, OR
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.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
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.\" BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
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.\" WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
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.\" OR OTHERWISE) RISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN
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.\" IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.NH
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Point Sizes; Line Spacing
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.PP
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As mentioned above,
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the command
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.BD .ps
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sets the point size.
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One point is 1/72 inch,
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so 6-point characters are at most 1/12 inch high,
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and 36-point characters are \(12 inch.
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There are 15 point sizes, listed below.
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.P1 1
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.ps 6
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6 point: Pack my box with five dozen liquor jugs.
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.ps 7
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.vs 8p
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7 point: Pack my box with five dozen liquor jugs.
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.vs 9p
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.ps 8
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8 point: Pack my box with five dozen liquor jugs.
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.vs 10p
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.ps 9
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9 point: Pack my box with five dozen liquor jugs.
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.vs 11p
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.ps 10
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10 point: Pack my box with five dozen liquor
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.vs 12p
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.ps 11
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11 point: Pack my box with five dozen
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.vs 14p
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.ps 12
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12 point: Pack my box with five dozen
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.vs 16p
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.ps 14
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14 point: Pack my box with five
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.vs 24p
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\s1616 point\s18 18 point\s20 20 point
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.vs 40p
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\s2222\s24 24\s28 28\s36 36
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.ps 10
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.vs 12p
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.P2
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.PP
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If the number after
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.BD .ps
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is not one of these
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legal sizes,
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it is rounded up to the next valid value,
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with a maximum of 36.
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If no number follows
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.BD .ps ,
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.UL troff
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reverts to the previous size, whatever it was.
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.UL troff
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begins with point size 10,
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which is usually fine.
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The original of this document (on 8.5 by 11 inch paper) is in 9 point.
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.PP
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The point size can also be changed in the middle of a line
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or even a word
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with the in-line command
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.BD \es .
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To produce
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.P1
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\s8UNIX\s10 runs on a \s8PDP-\s1011/45
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.P2
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type
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.P1
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\es8UNIX\es10 runs on a \es8PDP-\es1011/45
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.P2
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As above,
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.BD \es
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should be followed by a legal point size,
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except that
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.BD \es0
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causes the size to revert to
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its previous value.
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Notice that
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.BD \es1011
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can be understood correctly as `size 10, followed by an 11', if the size is legal,
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but not otherwise.
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Be cautious with similar constructions.
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.PP
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Relative size changes are also legal and useful:
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.P1
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\es\-2UNIX\es+2
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.P2
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temporarily decreases the size, whatever it is, by two points, then
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restores it.
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Relative size changes have the advantage that the size difference
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is independent of the starting size of the document.
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The amount of the relative change is restricted
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to a single digit.
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.WS
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.PP
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The other parameter that determines what the type looks like
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is the spacing between lines,
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which is set independently of the point size.
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Vertical spacing is measured from the bottom of one line to
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the bottom of the next.
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The command to control vertical spacing is
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.BD .vs .
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For running text, it is usually best to set the vertical spacing
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about 20% bigger than the character size.
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For example, so far in this document, we have used
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``9 on 11'', that is,
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.P1
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^ps 9
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^vs 11p
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.P2
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If we changed to
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.P1
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^ps 9
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^vs 9p
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.P2
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.vs 9p
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.ne 3
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the running text would look like this.
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After a few lines, you will agree it looks a little cramped.
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The right vertical spacing is partly a matter of taste, depending on how
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much text you want to squeeze into a given space,
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and partly a matter of traditional printing style.
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By default,
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.UL troff
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uses 10 on 12.
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.PP
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.vs 14p
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.ps 12
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Point size and vertical spacing make a substantial difference in the amount of text
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per square inch.
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This is 12 on 14.
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.ne 2
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.PP
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.ne 2
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.ps 6
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.vs 7p
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Point size and vertical spacing make a substantial difference in the amount of text
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per square inch.
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For example,
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10 on 12 uses about twice as much space as 7 on 8.
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This is 6 on 7, which is even smaller.
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It packs a lot more words per line,
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but you can go blind trying to read it.
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.PP
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When used without arguments,
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.BD .ps
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and
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.BD .vs
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revert to the previous size and vertical spacing
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respectively.
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.WS
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.PP
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The command
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.BD .sp
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is used to get extra vertical space.
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Unadorned,
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it gives you one extra blank line (one
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.BD .vs ,
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whatever that has been set to).
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Typically, that's more or less than you want,
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so
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.BD .sp
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can be followed by
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information about how much space you want _
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.P1
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^sp 2i
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.P2
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means `two inches of vertical space'.
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.P1
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^sp 2p
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.P2
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means `two points of vertical space';
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and
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.P1
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^sp 2
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.P2
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means `two vertical spaces' _ two of whatever
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.BD .vs
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is set to
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(this can also be made explicit with
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.BD .sp\ 2v );
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.UL troff
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also understands decimal fractions in most places,
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so
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.P1
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^sp 1.5i
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.P2
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is a space of 1.5 inches.
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These same scale factors can be used after
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.BD .vs
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to define line spacing, and in fact after most commands
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that deal with physical dimensions.
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.PP
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It should be noted that all size numbers are converted internally
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to `machine units', which are 1/432 inch
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(1/6 point).
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For most purposes, this is enough resolution
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that you don't have to worry about the accuracy of the representation.
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The situation is not quite so good vertically,
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where resolution is 1/144 inch
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(1/2 point).
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