reading number registers

\nY or \n(XX.

%

page number

.$

(r/o) number of macro arguments

.A

(r/o) nroff or troff -a

.H

(r/o) horizontal resultion, in units

.L

(r/o) current line spacing parameter (.ls)

.P

(r/o) 1 if current page is printed, else 0

.T

(r/o) nroff -T

.V

(r/o) vertical resolution, in units

.a

(r/o) most recently used post-line space from \x'N'

.c

(r/o) input line

.d

(r/o) vertical position in diversion, or nl if no diversion

.f

(r/o) font as physical quadrant (1-4) (huh?)

.h

(r/o) text baseline high-water mark (huh?)

.i

(r/o) indent

.j

(r/o) adjustment mode and type

.k

(r/o) horizontal text portion size of current output line

.l

(r/o) line length

.n

(r/o) length of text portion on previous output line

.o

(r/o) page offset

.p

(r/o) page length

.s

(r/o) point size

.t

(r/o) distance to next trap

.u

(r/o) fill mode? 1=yes, 0=no

.v

(r/o) vertical line spacing

.w

(r/o) width of previous character

.x

(r/o) (reserved)

.y

(r/o) (reserved)

.z

(r/o) name of current diversion (string)

c.

input line

ct

character type (set by width function) (huh?)

dl

maximum width of last completed diversion

dn

height of last completed diversion

dw

weekday (1-7)

dy

day of month (1-31)

hp

input column

ln

output line number

mo

month (1-12)

nl

vertical position of last printed text baseline

sb

depth of string below baseline, generated by width function

st

height of string above baseline, generated by width function

yr

year % 100 or year - 1900 [differs between implementations]