The conversion file of a Backpropagation Net must be used to convert ASCII characters (the net input) to an internal binary representation. The number of binary values that represent the ASCII characters can be changed freely, but has to be the same for each character.
The general structure of a conversion file is as follows:
In the first line:
Number of conversions
Each following line:
- At first position: The ASCII character
- and then: The binary representation (the length of this representation doesn't matter, but must be the same for each conversion)
Below you see the conversion file ascii2bin.cnv that is used in the BPN application. It contains 64 conversions (as can be seen in the first line) and each ASCII character is converted to 6 binary digits.
Note: A conversion file must be read before you add neuron layers to the net, because the number of binary digits must already be available when a neuron layer is created.