A dagger (
) next to a register name indicates that the register can
be set only from the command line or before the mm macro
definitions are read by the formatter.  Any register having a
single-character name can be set from the command line with the
-r option.
A![]()  | If set to 1, omit technical memorandum headings and provide spaces appropriate for letterhead (see .AF macro).  | 
| Au | Omit author information on first page (see .AU macro). | 
C![]()  | Flag indicating type of copy (original, draft, etc.). | 
| Cl | Level of headings saved for table of contents (see .TC macro). Default is 2.  | 
| Cp | If set to 1 (default), list of figures and tables appear on same page as table of contents. Otherwise, they start on a new page.  | 
D![]()  | If set to 1, use debug mode (  | 
| De | If set to 1, eject page after each floating display. Default is 0. | 
| Df | Set format of floating displays (see .DF macro). | 
| Ds | Set space used before and after static displays. | 
E![]()  | Font for Subject/Date/From. 0 (bold, the default) or 1 (roman). | 
| Ec | Equation counter, incremented for each .EC macro. | 
| Ej | Heading level for page eject before headings. Default is 0 and no eject. | 
| Eq | If set to 1, place equation label at left margin. Default is 0. | 
| Ex | Exhibit counter, incremented for each .EX macro. | 
| Fg | Figure counter, incremented for each .FG macro. | 
| Fs | Vertical spacing between footnotes. | 
Hn | Heading counter for level   | 
| Hb | Level of heading for which break occurs before output of body text. Default is 2.  | 
| Hc | Level of heading for which centering occurs. Default is 0. | 
| Hi | Type of indent after heading. Values are 0 (left-justified), 1 (indented, the default), 2 (indented except after .H, .LC, .DE).  | 
| Hs | Level of heading for which space after heading occurs. Default is 2. | 
| Ht | Numbering type of heading: 1 (single) or 0 (concatenated, the default). | 
| Hu | Set level of heading at which unnumbered headings occur. Default is 2.  | 
| Hy | If set to 1, enable hyphenation. Default is 0. | 
L![]()  | Set length of page. Default is 66v. | 
| Le | Flag to print list of equations after table of contents: 0 (don't print, the default) or 1 (print).  | 
| Lf | Like Le, but for list of figures. | 
| Li | Default indent of lists. Default is 5. | 
| Ls | Set spacing between items in nested lists. Default is 6 (spacing between all levels of list).  | 
| Lt | Like Le, but for list of tables. | 
| Lx | Like Le, but for list of exhibits. | 
N![]()  | Set page numbering style: 
  | 
| Np | Set numbering style for paragraphs: 0 (unnumbered) or 1 (numbered). | 
| O | Offset of page. For nroff, value is unscaled number representing character positions; default is 9 (7.5i). For troff, value is scaled; default is .5i.  | 
| Oc | Set numbering style for pages in table of contents: 0 (lowercase roman, the default) or 1 (arabic).  | 
| Of | Set separator for figure number in captions. 0 (use period, the default); 1 (use hyphen).  | 
| P | Current page number. | 
| Pi | Amount of indent for paragraph. Default is 5 for nroff and 3 for troff. | 
| Ps | Amount of spacing between paragraphs. Default is 3v. | 
| Pt | Paragraph type. Values are 0 (left-justified, the default), 1 (indented), 2 (indented except after .H, .LC, .DE).  | 
| Pv | Suppress ``PRIVATE" header. | 
| Rf | Reference counter, incremented for each .RS. | 
S![]()  | Default point size for troff. Default is 10. Vertical spacing is \nS+2.  | 
| Si | Standard indent for displays. Default is 5 for nroff and 3 for troff. | 
T![]()  | Type of nroff output device. Sets registers for specific devices.  | 
| Tb | Table counter, incremented for each .TB. | 
U![]()  | Style of nroff underlining for .H and .HU. If not set, use continuous underline; if set, don't underline punctuation and white space. Default is 0. | 
W![]()  | Width of page (line and title length). Default is 6i. |