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Both IRAF
and ZODIAC are
command-line based systems. Common user-level features include:
- Command-line interpreter with environment variables, command
history, expression parsing, optional command-line editing.
- Images stored as individual disk files.
- Simple syntax for accessing image sub-arrays.
- On-line task-specific help.
- Extensible through a simple scripting language.
Features particular to IRAF
include:
- Substantial use of environment variables (e.g., stdimage,
editor, graphcap).
- Organization of routines into package/task tree structure.
- Image headers maintain data description and processing history.
- Parameter system provides standard interface to all tasks.
Features particular to ZODIAC include:
- Interpreter with knowledge of mathematical expressions, for easy
manipulation of data, regardless of dimension.
- Simple binary disk format for image data.
- Support for 0-d constants.
From a user point of view,
IRAF
is substantially more
powerful and robust than ZODIAC. The presentation of each task in a
standard parameter system and the organization of tasks into packages
based upon function are extremely useful, given the large numbers of
tasks in these systems. (However, search routines, such as the
APROPOS task, are still necessary, as in UNIX.) The lack of
image header information in ZODIAC is a major problem, especially as
space-based observatories proliferate and ground-based instruments and
telescopes become more complex. The ability of ZODIAC to
mathematically manipulate multi-dimensional data (e.g., a=b+c, where
a, b, and c have arbitrary dimensions) is much more intuitive
than the IMEXPR and IMARITH tasks.
Next: Programming Interface
Up: Features of IRAF and
Previous: Features of IRAF and
Patrick Shopbell
8/7/1997