1. A method for performing a context switch in a central processing unit (CPU) comprising a plurality context defining register sets, wherein each set of registers having the same number of CPU registers; the method comprising: upon occurrence of an exception automatically switching to a register set of said plurality of context defining register sets, wherein selection of a register set of said plurality of context defining register can further be manually initiated by executing a context switch instruction; and indicating a currently used context in a first bitfield and a most recent context selected by said instruction in a second bitfield of a context status register.