Q. Describe Miscellaneous and Privileged Instructions?
These instructions don't fit in any of above categories. I/O instructions: start I/O, stop I/O, and test I/O. Characteristically I/O destination is specified as an address. Interrupts and state-swapping operations: There are two types of exceptions first is interrupts which are produced by traps andhardwarethat are produced by programs. Upon receiving interrupts the state of current processes would be saved so that they can be restarted after interrupt has been taken care of.
Most computer instructions are categorizedin two categories, non-privileged and privileged. A process executing in privileged mode can execute all instructions from instruction set whereas a process running in user mode can only execute a sub-set of the instructions. I/O instructions are one illustrations of privileged instruction, clock interrupts are another one.