4.3.7 Differences from AT&T ms

This section lists the (minor) differences between the groff -ms macros and AT&T troff -ms macros.

• The internals of groff -ms differ from the internals of AT&T troff -ms. Documents that depend upon implementation details of AT&T troff -ms may not format properly with groff -ms.
• The general error-handling policy of groff -ms is to detect and report errors, rather than silently to ignore them.
• groff -ms does not work in compatibility mode (this is, with the -C option).
• There is no special support for typewriter-like devices.
• groff -ms does not provide cut marks.
• Multiple line spacing is not supported. Use a larger vertical spacing instead.
• Some UNIX ms documentation says that the CW and GW number registers can be used to control the column width and gutter width, respectively. These number registers are not used in groff -ms.
• Macros that cause a reset (paragraphs, headings, etc.) may change the indentation. Macros that change the indentation do not increment or decrement the indentation, but rather set it absolutely. This can cause problems for documents that define additional macros of their own. The solution is to use not the in request but instead the RS and RE macros.
• To make groff -ms use the default page offset (which also specifies the left margin), the PO register must stay undefined until the first -ms macro is evaluated. This implies that PO should not be used early in the document, unless it is changed also: Remember that accessing an undefined register automatically defines it.

Register: \n[GS]

This number register is set to 1 by the groff -ms macros, but it is not used by the AT&T troff -ms macros. Documents that need to determine whether they are being formatted with AT&T troff -ms or groff -ms should use this number register.

Emulations of a few ancient Bell Labs macros can be re-enabled by calling the otherwise undocumented SC section-header macro. Calling SC enables UC for marking up a product or application name, and the pair P1/P2 for surrounding code example displays.

These are not enabled by default because (a) they were not documented, in the original ms manual, and (b) the P1 and UC macros collide with different macros with the same names in the Berkeley version of ms.

These groff emulations are sufficient to give back the 1976 Kernighan & Cherry paper Typsetting Mathematics – User’s Guide its section headings, and restore some text that had gone missing as arguments of undefined macros. No warranty express or implied is given as to how well the typographic details these produce match the original Bell Labs macros.