----------------           SIGNALS        ----------------------

      A PROGRAM TO ILLUSTRATE THE CONCEPTS OF LINEAR SYSTEMS,
        DIGITAL SIGNAL PROCESSING, AND COMPLEX NUMBERS.

              copyright 1994  Dr. Roger L. Easton, Jr. 

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*Starting SIGNALS*


SIGNALS checks for CGA, EGA, and VGA graphics and uses the highest
resolution available. 

To run on CGA, EGA, or VGA COLOR systems, type: SIGNALS/C.

On CGA, EGA, or VGA MONOCHROME systems, type: SIGNALS/M.

If color/monochrome switch is not used, the program asks whether the
system has a color or monochrome monitor.

To run SIGNALS with a HERCULES graphics card, the HERCULES graphics
driver 'msherc.com' must be loaded first. The color/monochrome switch is not 
needed on HERCULES.

On my own system, I renamed SIGNALS.EXE to SIGNALS1.EXE and wrote a
short batch program SIGNALS.BAT which loads the program with the proper
switch.

Sample batch programs are:

for HERCULES graphics:

     \path1\MSHERC.COM
     \path2\SIGNALS1.EXE

     where:
           \path1\ specifies subdirectory where MSHERC.COM is stored
           \path2\ specifies subdirectory for SIGNALS1.EXE

for CGA, EGA, or VGA color systems:
     \path2\SIGNALS1.EXE/C

for CGA, EGA, or VGA monochrome systems:
     \path2\SIGNALS1.EXE/M

----------------------------------------------------------------------
*RUNNING SIGNALS*


SIGNALS is built around four menus (FUNCTION, OPERATIONS, ARITHMETIC,
PLOTTING) that return to the MAIN menu via the ESCAPE key. Up to two
complex arrays are loaded from the FUNCTION menu and processed with the
OPERATIONS and ARITHMETIC menus.  The results can be viewed with the
PLOT menu. Hardcopy is possible via a 'Print Screen' dump or by saving
the data in a tad-delimited format readable by spreadsheets.

The program can be run under Windows if SIGNALS.PIF is created and the
graphics memory is increased. Graphic plots can be captured to the Windows
clipboard by typing 'ALT + Print Screen', and the plots may be manipulated
in a graphics program such as Adobe PhotoShop(TM) or Aldus PhotoStyler(TM)
or included in graphics presentation programs such as MicroSoft PowerPoint(TM).

The data arrays may be indexed over either the interval [0, N-1] or 
over [-N/2, N/2-1] (default) (e.g. over [0,255] or [-128,127] if N = 256.
The choice is made in the MAIN menu ("I" option) and transforms are computed
differently in the two cases according to the index convention. Load data 
into ARRAYS f1 or f2 from the FUNCTION MENU.

Functions are loaded in the order:
     1.      REAL PART (or MAGNITUDE)
     2.      Modulation of Real Part
     3.      IMAGINARY PART (or Phase)
     4.      Modulation of Imaginary part.

Any of these steps may be bypassed by typing a carriage return <CR>, and 
the loading procedure may be completed at any point by typing the ESCAPE key to
return to the MAIN Menu.

Please note that all operations assume that the arrays are in
REAL/IMAGINARY format; if you have loaded arrays in MAGNITUDE/PHASE
format, you should immediately convert them via option "R" in the
OPERATIONS menu. Arrays in SIGNALS are be saved to ("S" option in
the OPERATIONS menu) , and loaded from disk ("L" option in the OPERATIONS
menu in the following ASCII format:

Data element 1                number of samples N (integer - power of 2)

Elements 2 through N+1        real array (N floating point values)

Elements N+2 through 2N+1     imaginary array (N floating point values)



Data from other applications can be loaded into SIGNALS if it is edited 
accordingly.

Arrays can also be loaded and saved in a generic spreadsheet format 
which contains three columns separated by tabs: the sample index, the 
real floating point value, and the imaginary floating point value.

OPERATIONS are performed on a single array; they include FFT, DFT,
Hartley Transform, Walsh-Hadamard transform, complex conjugate, etc.

The ARITHMETIC menu combines the two arrays, e.g. sum, product, difference
ratio, convolution etc.

The PLOT menu is used to display the data as REAL/IMAGINARY parts, as
MAGNITUDE/PHASE, POWER (squared magnitude), Power in Decibels, or as
ARGAND diagrams (Imaginary part vs. Real Part). The VALUES of the data
arrays may also be displayed, and the VALUES display may be magnified
via the ZOOM option.


*REGISTRATION*

If you find SIGNALS to be useful and use it regularly, please register
your copy by sending your name, address, and $20 (check or money order) to
the address below.  You will receive a copy of a user manual, and will be
informed of any updates.

SIGNALS was developed for use in graduate classroom 
instruction over a period of several years. Many long hours went into
refining this program for public release.  Your registration fee will be
greatly appreciated and will expedite the release of future versions.

This program may be freely copied or posted on a BBS provided that all
three files are included in their original form with the copyright and
registration notices.

Please send the registration fee and any comments or suggestions to:

Dr. Roger L. Easton, Jr.
Center for Imaging Science 
Rochester Institute of Technology 
Rochester, NY 14623

(716) 475-5969 (office)
(716) 475-5988 (FAX)
email -- in%"rlepci@rit.edu"