Self-emulation is a technique used to run a computer's programs in a controlled environment on the same computer. There are two ways it can be done:

• Full emulation. Each instruction is interpreted. Bochs does this. Machine-level debuggers on machines without privileged instructions do this.
• Virtualization of privileged instructions. Instructions are executed natively until a General Protection Fault occurs, which means the program being emulated tried to execute a privileged instruction. This is faster than full emulation; VMWare uses virtualization.