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I read a lot of explanation of heap and stack memory, and all of them obscure anyway in terms of origin. First of all I understand how this memories works with software, but I don't understand the main source of this division. I assume that they are the same unspecialized physical memory, but...

For example say we have PC without any OS, and we want create some bootable program with assembly language for x86. I assume we can do this (Personally I don't know assembly, but some people write OS anyway). So the main question is Can we already operate with heap and stack, or we must create some memory managment machinery for this? If yes, so how it can be possible in terms of bare metal programming?

vt_artix
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    Possible duplicate of [What and where are the stack and heap?](https://stackoverflow.com/questions/79923/what-and-where-are-the-stack-and-heap) – Thilo Jan 27 '19 at 08:10

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Adding something to the other answer, fairly correct but perhaps not very complete.

Heap and stack are two (software) ways to "manage" memory. The physical memory, normally, is a flat array of cells where a program can read and write. It is up to the running program to use those cells as it wants. But there is more to say.

1^ thing. Heap is totally software, while stack is also (or mainly) a hardware thing. Most processors have hardware (or CPU instruction) to support the stack, while most (or all?) don't care about the heap. Even more: there are small embedded processors (or microcontrollers) which have a separated stack area - totally different from other ram areas where the program could create a "heap".

2^ thing. Whean speaking about "programs", one can/should think that the operating system (the OS) is a program, specialized in managing resources (memory included), and extendable with "applications" (which are programs). In such scenario, stack and heap are managed in cooperation from both OS and the applications.

So, to reply to your main question, the 90% correct answer is: in bare metal you have already a stack - perhaps you have to issue some short instruction to set it up, but it is straightforward. But you don't have a heap, you must implement it in your program. First you set aside some memory to be used as a stack; and then you can set aside some more memory to be used as a heap, not forgetting that you must preserve some memory for normal/static data. The part of the program that manages the heap should know what to do, using but not erratically overwriting the stack and the static data, to perform its functions.

linuxfan says Reinstate Monica
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  • The correct thing to do here would probably be to post this on the nominated duplicate question, and vote to close this one as a duplicate. – tripleee Jan 27 '19 at 08:47
  • @tripleee I could do it, but it seems to me that the other question, and its answers, are more high level than this question, and my answer. The other page is also very long. If you or someone other insist, then I can do it. – linuxfan says Reinstate Monica Jan 28 '19 at 06:28
  • No worries, let's keep it like this for now. – tripleee Jan 28 '19 at 07:05