4.6.7 Differences from AT&T ms

The groff ms macros are an independent reimplementation, using no AT&T code. Since they take advantage of the extended features of groff, they cannot be used with AT&T troff. groff ms supports features described above as Berkeley and Research Tenth Edition Unix extensions, and adds several of its own.

Register: \n[GS]

groff ms sets the register GS to 1; AT&T ms does not use it. A document can test its value to determine whether it is being formatted with groff ms or another implementation.