Operating system
Software virtualization: from real to abstract virtual machines

The role of an operating system is to virtualize a machine's peripherals and memory. The aim is to provide uniform access to hardware resources. The role of an operating system is not to virtualize the processor itself, as its purpose is to maintain good performance. Indeed, running an application natively on a processor is always faster than interpreting or re-compiling machine code at runtime. What's more, advanced languages partially mask different processor architectures. For example, a program written in C can be compiled for different processors, provided there is a compiler for the processor. So the same C program can be compiled for a 32-bit Pentium or 32-bit AMD processor, but also for a PowerPC, Sparc, 64-bit AMD or M68K processor. On the other hand, access to the processor is virtualized by an operating system to simulate the execution of several independent applications at the...