need some help with basic simulation

well, i guess here's another post about my simulation. i think some of you may have replyed or glanced over my previous posts, but if you haven't, let me fill you in. i'm creating an ecosystem simulation (called Eco-Sim, aren't i creative? lol), which is based on the simple math model -
(a/b*c) -(d/e*c)

So far it's a static sim, meaning there is no chance/probabliiy. Now that I'm done it, I would like someone to help me out, and tell me how to make this a dynamic sim (aka. chance oriented).

So far, this is my code -

Code:

//Coded By Jack Olszewski, Version 1.00
#include <stdio.h>
main()
{ 
      printf("Welcome to Eco-Sim!\n");
      printf("Version 1.00\n");
      printf("By Jack Olszwski\n");
      printf("\n");
      float a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p;
      printf("Time (1 = 1 Day):");  
      scanf ("%f",&c);
      printf("\n");
      printf("Plants:\n");
      printf("\n");
      printf("First Number of Creation (N/?):");
      scanf("%f",&a);
      printf("Second Number of Creation (?/N):");
      scanf("%f",&b);
      printf("First Number of Destruciton (N/?):");
      scanf("%f",&d);
      printf("Second Number of Destruction (?/N):");
      scanf("%f",&e);
      f=(a/b*c) -(d/e*c);
      printf("\n");
      printf("Herbivores:\n");
      printf("\n");
      printf("First Number of Creation (N/?):");
      scanf("%f",&g);
      printf("Second Number of Creation (?/N):");
      scanf("%f",&h);
      printf("First Number of Destruciton (N/?):");
      scanf("%f",&i);
      printf("Second Number of Destruction (?/N):");
      scanf("%f",&j);
      k=(g/h*c)-(i/j*c);
      printf("\n");
      printf("Carnivores:\n");
      printf("\n");
      printf("First Number of Creation (N/?):");
      scanf("%f",&l);
      printf("Second Number of Creation (?/N):");
      scanf("%f",&m);
      printf("First Number of Destruciton (N/?):");
      scanf("%f",&n);
      printf("Second Number of Destruction (?/N):");
      scanf("%f",&o);
      p=(g/h*c)-(i/j*c);
      printf("\n");
      printf("Final Amounts:\n");
      printf("\n");
      printf("Plants:%f\n",f);
      printf("Herbivores:%f\n",k); 
      printf("Carnivores:%f\n",p); 
}

Ty in advance,

JOlszewski

I'm not sure about your simulation, but I would strongly recommend you choose a more informative naming scheme for your variables than the letters of the alphabet in order.