Virtual address space
In computing, a virtual address space (VAS) is an area of contiguous virtual memory locations, called virtual addresses, which an operating system makes available to a process for executing instructions and storing data, and which it maps to the address space of physical addresses in a computer's hardware memory. The range of virtual addresses usually starts at a low address and can extend to the highest address allowed by the computer's instruction set architecture and supported by the operating system's pointer size implementation, which can be 4 bytes for 32-bit or 8 bytes for 64-bit OS versions.