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8.1.2.5 Obsolete Command

In AT&T troff output, the writing of a single glyph is mostly done by a very strange command that combines a horizontal move and a single character giving the glyph name. It doesn't have a command code, but is represented by a 3-character argument consisting of exactly 2 digits and a character.

ddg
Move right dd (exactly two decimal digits) basic units ‘u’, then print glyph g (represented as a single character).

In gtroff, arbitrary syntactical space around and within this command is allowed to be added. Only when a preceding command on the same line ends with an argument of variable length a separating space is obligatory. In AT&T troff, large clusters of these and other commands are used, mostly without spaces; this made such output almost unreadable.

For modern high-resolution devices, this command does not make sense because the width of the glyphs can become much larger than two decimal digits. In gtroff, this is only used for the devices X75, X75-12, X100, and X100-12. For other devices, the commands ‘t’ and ‘u’ provide a better functionality.