Means you pushed too hard and some popped out.
This is going back a ways, so it may not be 100% correct. However, I think the concept is more or less right. Nevertheless, I'm sticking my neck out so that someone else can call me an idiot and give an appropriate answer.
Basically the stack is a limited amount of internal storage in the central processor (CPU chip) of a computer where items of information can be temporarily kept in order, i.e., in a "stack." These items may be intermediate results or other external memory addresses, or instructions to the Central Processor Unit itself in temporary storage. Access to this "stack" of information is very fast since the information is stored right there in the processor itself.
You can "push" an item into the stack for storage, or you can "pop" it out to operate on it --whether it's a memory address or an intermediate result in a calculation. If you push too many items into the stack, without popping some out, it results in "stack overflow." This can be a result of a couple of things, like dividing by zero.
"Push" and "pop" are actual assembly language commands. One too many pushes or one too few pops and the stack overflows.
A very, very, very long time ago I used to know the actual binary commands for push and pop for the Intel 8000 series of CPUs. Virtually useless knowledge nowadays anyhow.
Terry "with apologies," 230RN
