Process memory layout windows

Privacy policy. The virtual address space for a process is the set of virtual memory addresses that it can use. The address space for each process is private and cannot be accessed by other processes unless it is shared.

A virtual address does not represent the actual physical location of an object in memory; instead, the system maintains a page table for each process, which is an internal data structure used to translate virtual addresses into their corresponding physical addresses.

Just think about the various needs and you can probably figure out why the operating system does what it does. Not all memory is available for use by applications. For example, some types of hardware require memory so the system BIOS or OS will allocate a block of physical memory and leave it for the hardware to manage itself. That memory may not be directly readable or writable because performing such operations would affect the hardware.

The hardware itself may have its own restrictions about what memory ranges it can use. If you're in Windows, you can't go writing to arbitrary memory locations - the OS won't let you in usermode at least and will have paged the memory anyway, so the address you think you're looking at the virtual address won't match the actual physical memory address.

In general, you should only read and write to memory that has been requested and allocated to you by the OS. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Collectives on Stack Overflow. Learn more. Asked 9 years, 11 months ago. Active 9 years, 11 months ago. Viewed 2k times. About those lower 2GB of space: Why are there those gaps?

Thank you for reading this question. EDIT Ah here we go with what's at 0x and that's also probably why that page is let writable. Improve this question. Community Bot 1 1 1 silver badge. The newly called function then allocates room on the stack for its automatic and temporary variables.

This is how recursive functions in C can work. Heap: Heap is the segment where dynamic memory allocation usually takes place. The heap area begins at the end of the BSS segment and grows to larger addresses from there.

The Heap area is shared by all shared libraries and dynamically loaded modules in a process. The size 1 command reports the sizes in bytes of the text, data, and bss segments. Let us add one global variable in the program, now check the size of bss highlighted in red color.

Let us add one static variable which is also stored in bss. Let us initialize the static variable which will then be stored in the Data Segment DS. Skip to content. Change Language. Related Articles. Table of Contents. The first answer is that the first diagram is simply not applicable to Windows. Not even to NT 3. It is not applicable to VMS either. It appears to be a variant of something that was probably drawn regarding Unix in the s.

Note that there is not even allowance for things like thread-local storage or per-thread stacks! Just ignore it, and be amused that it's still being copied. The second answer is "none of the above". It does not come out of existing heap, stack, or memory mapping space.

Nor is there any such thing as a region pre-designated for e. Each new allocation is created from unallocated virtual address space and there is no reason for all the memory mappings, all of the heaps, etc. Oh, and by the way, none of those are "segments".