Overview

The virtual address space (VAS) is the range of memory addresses that a process can use. Windows maps the VAS to physical memory using a combination of paging, address translation, and protection mechanisms.

Address Space Layout

Key API Functions

#include <windows.h>

// Allocate a region of virtual memory
LPVOID addr = VirtualAlloc(
    NULL,               // Let the system choose the address
    4096,               // Size of allocation (bytes)
    MEM_RESERVE | MEM_COMMIT,
    PAGE_READWRITE
);

// Query information about a region
MEMORY_BASIC_INFORMATION mbi;
SIZE_T result = VirtualQuery(addr, &mbi, sizeof(mbi));
if (result) {
    printf("BaseAddress: %p\n", mbi.BaseAddress);
    printf("RegionSize:  %zu\n", mbi.RegionSize);
    printf("State:       %u\n", mbi.State);
}

// Release the memory
VirtualFree(addr, 0, MEM_RELEASE);

Best Practices

• Prefer higher‑level allocators (HeapAlloc, malloc) unless you need precise control.
• Always check the return values of VirtualAlloc, VirtualProtect, and VirtualFree.
• Use Guard Pages to detect stack overflows.
• Align allocations to page boundaries when mapping files.
• Release memory promptly to avoid address space fragmentation.

FAQ