!PCM Demo V1.0 1992 by Dharmesh Khatri
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!PCM Demo is a small program to demonstrate the method of Pulse Code
Modulation which is used in communications. The reason for writing this
program is that one of my friends wanted a simulation of PCM. When you load
the program you will see three boxes.  In the first put in the wave using
the mouse. This is done by moving your mouse on to the lift hand side of the
box, then press the SELECT button on the mouse to draw the wave. Once this
is done press the ADJUST button on the mouse.

In the second box a row of parallel lines will be printed on the screen,
they represent a digital version of the original wave. (The program takes
the values of a point (on the wave) and turns it into a binary number). On
the third box the digital numbers are turned into decimal, these levels are
shown. When you press the Space Bar, the peeks of each line will be joined
to one another to show a wave. In certain waves the output may not look
exactly the same as the original. This is due to the sampling speed. The
binary numbers will also be printed. These are printed on the right.

If you press the SELECT button on the 'SINE WAVE', a sine wave will be drawn
and all the rest will be done. 

Technical Details about the program
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This program is done on mode 16, this is because I can get all the data in  
one whole screen. I have slowed down the mouse step so the computer will
take proper readings, and not miss any out. The box you draw your wave on is
1000 long and 256 up. The sampling rate is  1000/25, this means that it
takes a reading after every 25 pixels. The program takes a Maxium of 40
readings.
