1. \"DS - display. If .DS C, center; L, left-adjust; I, indent. 2.de DS 3.KS 4.nf 5.\\$1D \\$2 \\$1 6.ft 1 7.ps \\n(PS 8.if \\n(VS>40 .vs \\n(VSu 9.if \\n(VS<=39 .vs \\n(VSp 10.. 11.de D 12.ID \\$1 13.. 14.de CD 15.XD 16.ce 1000 17.. 18.de ID 19.XD 20.if t .in +0.5i 21.if n .in +8 22.if \\n(.$ .if !"\\$1"I" .if !"\\$1"" .in \\n(OIu 23.if \\n(.$ .if !"\\$1"I" .if !"\\$1"" .in +\\$1n 24.. 25.de LD 26.XD 27.. 28.de XD 29.nf 30.nr OI \\n(.i 31.if t .sp 0.5 32.if n .sp 1 33.. 34.de BD \" block display: save everything, then center it. 35.XD 36.nr BD 1 37.nf 38.in \\n(OIu 39.di DD 40.. 41. \"DE - display end 42.de DE 43.ce 0 44.if \\n(BD>0 .DF 45.nr BD 0 46.in \\n(OIu 47.KE 48.if t .sp 0.5 49.if n .sp 1 50.fi 51.. 52.de DF \" finish a block display to be recentered. 53.di 54.if \\n(dl>\\n(BD .nr BD \\n(dl 55.if \\n(BD<\\n(.l .in (\\n(.lu-\\n(BDu)/2u 56.nr EI \\n(.l-\\n(.i 57.ta \\n(EIuR 58.DD 59.in \\n(OIu 60.. 61