A source line with a TAB character anywhere in it is treated as
entirely significant--however long it is--instead of ending in
column 72 (for fixed-form source) or 132 (for free-form source).
This also is different from f2c, which encodes tabs as
`\t' (the ASCII TAB character) inside character
and Hollerith constants, but nevertheless seems to treat the column
position as if it had been affected by the canonical tab positioning.
g77 effectively
translates tabs to the appropriate number of spaces (a la the default
for the UNIX expand command) before doing any other processing, other
than (currently) noting whether a tab was found on a line and using this
information to decide how to interpret the length of the line and continued
constants.
Note that this default behavior probably will change for version 0.6, when it will presumably be available via a command-line option. The default as of version 0.6 is planned to be a "pure visual" model, where tabs are immediately converted to spaces and otherwise have no effect, so the way a typical user sees source lines produces a consistent result no matter how the spacing in those source lines is actually implemented via tabs, spaces, and trailing tabs/spaces before newline. Command-line options are likely to be added to specify whether all or just-tabbed lines are to be extended to 132 or full input-line length, and perhaps even an option will be added to specify the truncated-line behavior to which some Digital compilers default (and which affects the way continued character/Hollerith constants are interpreted).
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