readonly

 Readonly variables are assigned the PSECT attribute NOWRT and are
 stored in the PSECT $READONLY$ which is a nonwritable data area.
 Other programs can access the PSECT directly, but none of the
 information can be overwritten.  You can use the readonly modifier
 with the storage-class keywords [extern], static, globaldef, and
 globaldef{"name"}.

 You can use both the readonly and noshare modifiers with the
 [extern] and the globaldef{"name"} specifiers.  If you use both
 modifiers with either the static or the globaldef specifiers, the
 compiler ignores noshare and accepts readonly.