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| Chapter 12 Nroff and Troff |

## 12.4 Default Operation of Requests

Nroff/troff initializes the formatting environment. For example, unless you reset the line length, nroff/troff uses 6.5 inches. Most requests can change the default environment, and those that can are listed in the table below. The second column lists the initial or default value in effect before the request is used. If no initial value applies, a hyphen (-) is used. The third column shows the effect if a request's optional argument is not used. Here, a hyphen is used if the request doesn't accept an argument or if the argument is required.

Request | Initial | If No | Description
--- | --- | --- | ---
| Value | Argument |
.ad | Justify | Previous adjust | Adjust margins.
.af | Lowercase arabic | - | Assign a format to a register.
.am | - | End call with `..` | Append to a macro.
.bd | Off | - | Embolden font.
.c2 | `;` | `;` | Set no-break control character.
.cc | `.` | `.` | Set control character.
.ce | Off | Center one line | Center lines.
.ch | - | Turn off trap | Change trap position.
.cs | Off | - | Set constant-width spacing.
.cu | 0 | 1 line | Continuous underline/italicize.
.da | - | End the diversion | Divert text and append to a macro.
.de | - | End macro with `..` | Define a macro.
.di | - | End the diversion | Divert text to a macro.
.dt | - | Turn off trap | Set a diversion trap.
.ec | \ | \ | Set escape character.
.eo | On | - | Turn off escape character.
.ev | 0 | Prev. environment | Change environment.
.fc | Off | Off | Set field delimiter and pad character.
.fi | Fill | - | Fill lines.
.fp | 1 = R | - | Mount font (on positions 1-4).
| 2 = I |  |
| 3 = B |  |
| 4 = S |  |
.ft | Roman | Previous font | Set font.
.hc | \% | \% | Set hyphenation character.
.hy | Mode 1 | Previous mode | Set hyphenation mode.
.ig | - | End with `..` | Suppress (ignore) text in output.
.in | 0 | Previous indent | Indent.
.it | - | Turn off trap | Set a trap for input line counting.
.lc | `.` | None | Set leader character.
.lg | On | On | Ligature mode.
.ll | 6.5" | Prev. line length | Set line length.
.ls | Single-space | Previous mode | Set line spacing.
.lt | 6.5" | Prev. title length | Set length of title.
.mc | - | Turn off | Set the margin character.
.mk | - | Internal | Mark vertical position.
.na | Adjust | - | Don't adjust margins.
.ne | - | One vertical line | Keep lines on same page if there's room.
.nf | Fill | - | Don't fill lines.
.nh | On | - | Turn of hyphenation.
.nm | Off | Off | Line-numbering mode.
.nn | - | Number one line | Don't number lines.
.ns | Space mode | - | Enable no-space mode.
.nx | - | End of file | Go to a file.
.pc | % | Off | Set page character.
.pl | 11" | 11" | Set page length.
.pn | Page 1 | - | Set page number.
.po | 0 (nroff) | Previous offset | Change page offset.
| 26/27" (troff) |  |
.ps | 10 | Prev. point size | Set point size.
.rd | - | Ring bell | Read from the terminal.
.rt | - | Internal | Return to marked vertical place.
.sp | - | One vertical line | Output blank spacing.
.ss | 12/36 em | - | Set character spacing.
.sv | - | One vertical line | Save (store) spacing.
.ta | .5" (troff) | - | Define tab settings.
| 8 em (nroff) |  |
.ti | 0 | - | Indent next line.
.tm | - | Newline | Print a message, then continue.
.uf | Italic | Italic | Set font for underlining.
.ul | 0 | 1 line | Underline/italicize.
.vs | 1/6" (nroff) | Previous value | Set vertical spacing for lines.
| 12 pts (troff) |  |

12.3 Using the Requests: An Overview |  | 12.5 Group Summary of Requests