.NHFonts and Special Characters.PP.UL troffand the typesetter allow four different fonts at any one time.Normally three fonts (Times roman, italic and bold) and one collection of special charactersare permanentlymounted..P1 2.ft Rabcdefghijklmnopqrstuvwxyz 0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ.ft Iabcdefghijklmnopqrstuvwxyz 0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ.ft Babcdefghijklmnopqrstuvwxyz 0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ.ft R.P2Thegreek, mathematical symbols and miscellanyof the special font arelisted in Appendix A..PP.UL troffprints in roman unless told otherwise.To switch into bold, usethe.BD .ftcommand.P1^ft B.P2and for italics,.P1^ft I.P2To return to roman, use.BD .ft\ R ;to return to the previous font,whatever it was,use either.BD .ft\ Por just.BD .ft  .The `underline' command.P1^ul.P2causes the next input line to print in italics..BD .ulcan be followed by a count toindicate that more than one line is to be italicized..PPFonts can also be changed within a line or wordwith the in-line command.BD \ef :.P1\fBbold\fIface\fR text.P2is produced by.P1\efBbold\efIface\efR text.P2If you want to do this so the previous font, whatever it was,is left undisturbed, insert extra.BD \efPcommands, like this:.P1\efBbold\efP\efIface\efP\efR text\efP.P2Because only the immediately previous font is remembered,you have to restore the previous font after each changeor you can lose it.The same is true of .BD .psand.BD .vswhen used without an argument..PPThere are other fonts available besides the standard set,although you can still use only four at any given time.The command.BD .fptells.UL troffwhat fonts are physically mounted on the typesetter:.P1^fp 3 H.P2says that the Helvetica font is mounted on position 3.(For a complete list of fonts and what they look like,see the .UL troff manual.)Appropriate.BD .fpcommands should appear at the beginning of your documentif you do not use the standard fonts..PPIt is possible to make a document relatively independentof the actual fonts used to print itby using font numbers instead of names;for example,.BD \ef3and.BD .ft~3mean `whatever font is mounted at position 3',and thus work for any setting.Normal settings are roman font on 1, italic on 2,bold on 3,and special on 4..PPThere is also a way to get `synthetic' bold fontsby overstriking letters with a slight offset.Look at the.BD .bdcommand in [1]..WS.PPSpecial characters have four-character names beginning with.BD \e( ,and they may be inserted anywhere.For example,.P1\(14 + \(12 = \(34.P2is produced by.P1\e(14 + \e(12 = \e(34.P2In particular,greek letters are all of the form.BD  \e(*\- ,where.BD \-is an upper or lower case roman letterreminiscent of the greek.Thusto get.P1\(*S(\(*a\(mu\(*b) \(-> \(if.P2in bare.UL troffwe have to type.P1\e(*S(\e(*a\e(mu\e(*b) \e(\(mi> \e(if.P2That line is unscrambled as follows:.P1.ta 1i 2i 3i\e(*S	\(*S(	(\e(*a	\(*a\e(mu	\(mu\e(*b	\(*b)	)\e(\(mi>	\(->\e(if	\(if.P2A complete list of these special names occurs in Appendix A..PPIn.UL eqn [2]the same effect can be achieved with the input.P1SIGMA ( alpha times beta ) \-> inf.P2which is less concise, but clearer to the uninitiated..PPNotice thateachfour-character name is a single characteras far as.UL troffis concerned _the`translate' command.P1^tr \e(mi\e(em.P2is perfectly clear, meaning.P1^tr \(mi\(em.P2that is, to translate \(mi into \(em..PPSome characters are automatically translated into others:grave  \(ga  and acute  \(aa  accents (apostrophes) become open and close single quotes`~';the combination of ``...'' is generally preferable to the double quotes "...".Similarly a typed minus sign becomes a hyphen -.To print an explicit \- sign, use.BD \e- .To get a backslash printed, use.BD \ee .