as.info: Dot

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The Special Dot Symbol

   The special symbol `.' refers to the current address that `as' is
assembling into.  Thus, the expression `melvin: .long .' defines
`melvin' to contain its own address.  Assigning a value to `.' is
treated the same as a `.org' directive.  Thus, the expression `.=.+4'
is the same as saying `.space 4'.