/share/doc/usd/22.trofftut/tt02
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- .\" This module is believed to contain source code proprietary to AT&T.
- .\" Use and redistribution is subject to the Berkeley Software License
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- .\"
- .\" @(#)tt02 8.1 (Berkeley) 6/8/93
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- .\" $FreeBSD$
- .\"
- .NH
- Point Sizes; Line Spacing
- .PP
- As mentioned above,
- the command
- .BD .ps
- sets the point size.
- One point is 1/72 inch,
- so 6-point characters are at most 1/12 inch high,
- and 36-point characters are \(12 inch.
- There are 15 point sizes, listed below.
- .P1 1
- .ps 6
- 6 point: Pack my box with five dozen liquor jugs.
- .ps 7
- .vs 8p
- 7 point: Pack my box with five dozen liquor jugs.
- .vs 9p
- .ps 8
- 8 point: Pack my box with five dozen liquor jugs.
- .vs 10p
- .ps 9
- 9 point: Pack my box with five dozen liquor jugs.
- .vs 11p
- .ps 10
- 10 point: Pack my box with five dozen liquor
- .vs 12p
- .ps 11
- 11 point: Pack my box with five dozen
- .vs 14p
- .ps 12
- 12 point: Pack my box with five dozen
- .vs 16p
- .ps 14
- 14 point: Pack my box with five
- .vs 24p
- \s1616 point\s18 18 point\s20 20 point
- .vs 40p
- \s2222\s24 24\s28 28\s36 36
- .ps 10
- .vs 12p
- .P2
- .PP
- If the number after
- .BD .ps
- is not one of these
- legal sizes,
- it is rounded up to the next valid value,
- with a maximum of 36.
- If no number follows
- .BD .ps ,
- .UL troff
- reverts to the previous size, whatever it was.
- .UL troff
- begins with point size 10,
- which is usually fine.
- The original of this document (on 8.5 by 11 inch paper) is in 9 point.
- .PP
- The point size can also be changed in the middle of a line
- or even a word
- with the in-line command
- .BD \es .
- To produce
- .P1
- \s8UNIX\s10 runs on a \s8PDP-\s1011/45
- .P2
- type
- .P1
- \es8UNIX\es10 runs on a \es8PDP-\es1011/45
- .P2
- As above,
- .BD \es
- should be followed by a legal point size,
- except that
- .BD \es0
- causes the size to revert to
- its previous value.
- Notice that
- .BD \es1011
- can be understood correctly as `size 10, followed by an 11', if the size is legal,
- but not otherwise.
- Be cautious with similar constructions.
- .PP
- Relative size changes are also legal and useful:
- .P1
- \es\-2UNIX\es+2
- .P2
- temporarily decreases the size, whatever it is, by two points, then
- restores it.
- Relative size changes have the advantage that the size difference
- is independent of the starting size of the document.
- The amount of the relative change is restricted
- to a single digit.
- .WS
- .PP
- The other parameter that determines what the type looks like
- is the spacing between lines,
- which is set independently of the point size.
- Vertical spacing is measured from the bottom of one line to
- the bottom of the next.
- The command to control vertical spacing is
- .BD .vs .
- For running text, it is usually best to set the vertical spacing
- about 20% bigger than the character size.
- For example, so far in this document, we have used
- ``9 on 11'', that is,
- .P1
- ^ps 9
- ^vs 11p
- .P2
- If we changed to
- .P1
- ^ps 9
- ^vs 9p
- .P2
- .vs 9p
- .ne 3
- the running text would look like this.
- After a few lines, you will agree it looks a little cramped.
- The right vertical spacing is partly a matter of taste, depending on how
- much text you want to squeeze into a given space,
- and partly a matter of traditional printing style.
- By default,
- .UL troff
- uses 10 on 12.
- .PP
- .vs 14p
- .ps 12
- Point size and vertical spacing make a substantial difference in the amount of text
- per square inch.
- This is 12 on 14.
- .ne 2
- .PP
- .ne 2
- .ps 6
- .vs 7p
- Point size and vertical spacing make a substantial difference in the amount of text
- per square inch.
- For example,
- 10 on 12 uses about twice as much space as 7 on 8.
- This is 6 on 7, which is even smaller.
- It packs a lot more words per line,
- but you can go blind trying to read it.
- .PP
- When used without arguments,
- .BD .ps
- and
- .BD .vs
- revert to the previous size and vertical spacing
- respectively.
- .WS
- .PP
- The command
- .BD .sp
- is used to get extra vertical space.
- Unadorned,
- it gives you one extra blank line (one
- .BD .vs ,
- whatever that has been set to).
- Typically, that's more or less than you want,
- so
- .BD .sp
- can be followed by
- information about how much space you want _
- .P1
- ^sp 2i
- .P2
- means `two inches of vertical space'.
- .P1
- ^sp 2p
- .P2
- means `two points of vertical space';
- and
- .P1
- ^sp 2
- .P2
- means `two vertical spaces' _ two of whatever
- .BD .vs
- is set to
- (this can also be made explicit with
- .BD .sp\ 2v );
- .UL troff
- also understands decimal fractions in most places,
- so
- .P1
- ^sp 1.5i
- .P2
- is a space of 1.5 inches.
- These same scale factors can be used after
- .BD .vs
- to define line spacing, and in fact after most commands
- that deal with physical dimensions.
- .PP
- It should be noted that all size numbers are converted internally
- to `machine units', which are 1/432 inch
- (1/6 point).
- For most purposes, this is enough resolution
- that you don't have to worry about the accuracy of the representation.
- The situation is not quite so good vertically,
- where resolution is 1/144 inch
- (1/2 point).