dlaczego :(

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define size 81
int main(void)
{
    int i=0, j=0;
    char *tab;
    char *tab_p;
    char *tab_e;
    //alokuje pamiec dla tablic
    tab  =(char*)malloc(sizeof *tab *(size+1));
    tab_p=malloc(sizeof *tab_p *(size+1));
    tab_e=malloc(sizeof *tab_e *(size+1));
    //wypelniam tablice
    memset(tab, '-', size);
    *(tab+20)='x';

    memset(tab_p, '-', size);

    for(i=0; i<size; i++)
    {
        if(i%2==0)
            *(tab_e+i)='-';
        else
            *(tab_e+i)='x';
    }
    printf("%s \n", tab); //wypisuje tablice

    while(1)
    {
        for(i=0; i<size; i++)
        {
            if(tab[i-1]=='x' && tab[i]=='x' && tab[i+1]=='x')
                tab_p[i]='-';
            if(tab[i-1]=='x' && tab[i]=='x' && tab[i+1]=='-')
                tab_p[i]='-';
            if(tab[i-1]=='x' && tab[i]=='-' && tab[i+1]=='x')
                tab_p[i]='-';
            if(tab[i-1]=='x' && tab[i]=='-' && tab[i+1]=='-')
                tab_p[i]='x';
            if(tab[i-1]=='-' && tab[i]=='x' && tab[i+1]=='x')
                tab_p[i]='x';
            if(tab[i-1]=='-' && tab[i]=='x' && tab[i+1]=='-')
                tab_p[i]='x';
            if(tab[i-1]=='-' && tab[i]=='-' && tab[i+1]=='x')
                tab_p[i]='x';
            if(tab[i-1]=='-' && tab[i]=='-' && tab[i+1]=='-')
                tab_p[i]='-';
            /*
            if(i=0) //graniczne warunki dla poczatku ale nie działają
            {
                if(tab[i]=='x' && tab[i+1]=='x')
                    tab_p[i]='x';
                if(tab[i]=='x' && tab[i+1]=='-')
                    tab_p[i]='-';
                if(tab[i]=='-' && tab[i+1]=='-')
                    tab_p[i]='x';
                if(tab[i]=='-' && tab[i+1]=='x')
                    tab_p[i]='-';
            }
            if(i=size-1)
            {
                if(tab[i-1]=='x' && tab[i]=='x')
                    tab_p[i]='x';
                if(tab[i+1]=='x' && tab[i]=='-')
                    tab_p[i]='-';
                if(tab[i+1]=='-' && tab[i]=='-')
                    tab_p[i]='x';
                if(tab[i+1]=='-' && tab[i]=='x')
                    tab_p[i]='-';
            }*/
        }
        //kopiuje tablice
        memcpy(tab, tab_p, size);
        printf("%s", tab);
        if(strcmp(tab, tab_e)==0)  //sprawdzam czy sa takie same
        {
            printf("\n Licza krokow to %d \n", j);
            free(tab);
            free(tab_e);
            free(tab_p);
            return 0;
        }


    printf("\n");
    j++;    //jesli if nie jest spelniony to inkrementuje
    }
}