Filling (The GNU Troff Manual)

#### 5.1.1 Filling

When GNU `troff` starts up, it obtains information about the device for which it is preparing output.18 An essential property is the length of the output line, such as “6.5 inches”.

GNU `troff` interprets plain text files employing the Unix line-ending convention. It reads input a character at a time, collecting words as it goes, and fits as many words together on an output line as it can—this is known as filling. To GNU `troff`, a word is any sequence of one or more characters that aren’t spaces or newlines. The exceptions separate words.19 To disable filling, see Manipulating Filling and Adjustment.

    It is a truth universally acknowledged
    that a single man in possession of a
    good fortune must be in want of a wife.
        ⇒ It is a truth universally acknowledged that a
        ⇒ single man in possession of a good fortune must
        ⇒ be in want of a wife.