Comments command - Mailing list pgsql-sql

I'm running Postgresql 6.3.2.

When ones gets help on the built-in commands that start with '\' there is
a command '\dd [object]'. In the comments is says that it lists the
comment for the object, eg. table, field etc.

Is this command operative under 6.3.2? If so, how does one get the
comment(s) into those objects? The '\h create table' etc gives no idea.
Also which of the system tables (pg_?) are these comments written to?

Thanks.

Cheers...Gordon
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