access violation (segmentation fault)

[MarlonDean]

Why does this code cause my program to crash with the error "access violation (segmentation fault)"? and what is it?

for (counter=0;counter<UsedSpace;counter++)
{
   if (Numbers1[counter]<Numbers2[counter])
     {
     sort[counter]=Numbers1[counter];
     }
     else sort[counter]=Numbers2[counter];
}

thanks in advance