as: Input Files

1 
1 1.5 Input Files
1 ===============
1 
1 We use the phrase "source program", abbreviated "source", to describe
1 the program input to one run of 'as'.  The program may be in one or more
1 files; how the source is partitioned into files doesn't change the
1 meaning of the source.
1 
1    The source program is a concatenation of the text in all the files,
1 in the order specified.
1 
1    Each time you run 'as' it assembles exactly one source program.  The
1 source program is made up of one or more files.  (The standard input is
1 also a file.)
1 
1    You give 'as' a command line that has zero or more input file names.
1 The input files are read (from left file name to right).  A command line
1 argument (in any position) that has no special meaning is taken to be an
1 input file name.
1 
1    If you give 'as' no file names it attempts to read one input file
1 from the 'as' standard input, which is normally your terminal.  You may
1 have to type <ctl-D> to tell 'as' there is no more program to assemble.
1 
1    Use '--' if you need to explicitly name the standard input file in
1 your command line.
1 
1    If the source is empty, 'as' produces a small, empty object file.
1 
1 Filenames and Line-numbers
1 --------------------------
1 
1 There are two ways of locating a line in the input file (or files) and
1 either may be used in reporting error messages.  One way refers to a
1 line number in a physical file; the other refers to a line number in a
1 "logical" file.  ⇒Error and Warning Messages Errors.
1 
1    "Physical files" are those files named in the command line given to
1 'as'.
1 
1    "Logical files" are simply names declared explicitly by assembler
1 directives; they bear no relation to physical files.  Logical file names
1 help error messages reflect the original source file, when 'as' source
1 is itself synthesized from other files.  'as' understands the '#'
1