Input Files
===========

   We use the phrase "source program", abbreviated "source", to
describe the program input to one run of `as'.  The program may be in
one or more files; how the source is partitioned into files doesn't
change the meaning of the source.

   The source program is a concatenation of the text in all the files,
in the order specified.

   Each time you run `as' it assembles exactly one source program.  The
source program is made up of one or more files.  (The standard input is
also a file.)

   You give `as' a command line that has zero or more input file names.
The input files are read (from left file name to right).  A command
line argument (in any position) that has no special meaning is taken to
be an input file name.

   If you give `as' no file names it attempts to read one input file
from the `as' standard input, which is normally your terminal.  You may
have to type <ctl-D> to tell `as' there is no more program to assemble.

   Use `--' if you need to explicitly name the standard input file in
your command line.

   If the source is empty, `as' will produce a small, empty object file.

Filenames and Line-numbers
--------------------------

   There are two ways of locating a line in the input file (or files)
and either may be used in reporting error messages.  One way refers to
a line number in a physical file; the other refers to a line number in a
"logical" file.  See Error and Warning Messages: Errors.

   "Physical files" are those files named in the command line given to
`as'.

   "Logical files" are simply names declared explicitly by assembler
directives; they bear no relation to physical files.  Logical file names
help error messages reflect the original source file, when `as' source
is itself synthesized from other files.  See `.app-file': App-File.