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Chapter VI.  Standard Files and their Contents


     In this chapter we describe the functions and structures of the
various standard files or file types used in the AIPS system.  For
each file type, we also describe in some detail the standard routines
and commons which are used to read and write the files.  Our bias
toward INTEGER*2 words is clearly illustrated throughout.  However, we
have tried to write the descriptions in a way which makes it clear how
the files are structured on machines having different word length.
The standard routines contain special code to handle such problems.

     There are three types of standard files.  There are permanent
binary files which are, mostly, on the system disk (volume 1).  There
are temporary files containing image data and extensions of those data.
Such files may be located on any disk, but all associated files must be
on the same disk.  There are also permanent text files located on the
system disk which provide the INPUTS and HELP functions.  On VAX
systems, all files in the first two catagories exist under logon
[AIPS], while the INPUTS are found under logon [INPUTS] and the HELPs
are found under logon [HELP].  On MODCOMP systems, the INPUTS are
members of the source file IN100000 and the HELPs are members of the
source file HE100000.

     Many programs also require scratch files.  These are temporary
files whose structure, function, and contents are solely the responsi-
bility  of the individual program.  The prologue comments for such
programs should provide a description of these files.
