The generation of cell parameters and coefficients inside the permited levels of variation, and the decision upon the occourence of random events such as the early afterdepolarizations are governed by a series of ``pseudorandom'' numbers. This is a list of numbers which, when examined, do not show any rule of variation, that is there is no obvious or simple way of finding out what the next such number will be. Yet, they are pseudorandom because it is possible to reproduce the whole series exactly, by specifying a small amount of information called random seed.
In other words, despite the extensive generation of random values in the cord model (all cell parameters--within the ranges set by their cathegories, and in every cycle to see if the afterdepolarizations occur) the whole simulation will be reproduced exactly if the random seed is preserved untouched and, of course, the cord model and the external conditions are also unchanged. If it is changed no matter how little, the probability dependent parameters, coefficients and events change, all, in a completely unpredictable way--but within their ranges of variation.
What is more, if some other external parameters are changed, such as the placement of electrodes or an external factor, and the simulation is run again, with the same random seed, the change of the external factor will take place over the conditions as for the simulation with conditions unchanged.
The random seed in clarrhmos is specified by a string of characters (letter, digits, special signs) and a number. For example "Clarrhmos 2.0 is a great program." and 1000. The series of pseudorandom numbers is obtained by assigning fixed codes to the characters and then combining the codes arrhythmetically ad infinitum. The number is the number of combinations which are done and ignored before the actual pseudorandom numbers begin to be used. There should not be less than 5 characters in the string, and more than 55 are useless. The number should be between 1000 and 30000.