OPERATING-SYSTEM OPERATIONS o Interrupt driven by hardware 0 Software error or request creates exception or trap Division by zero,request for operating system service o Other process problems include infinite loop,processes modifying each other or the operating system o Dual-mode operation allows Os to protect itself and other system components User mode and kernel mode Mode bit provided by hardware o Provides ability to distinguish when system is running user code or kernel code o Some instructions designated as privileged,only executable in kernel mode o System call changes mode to kernel,return from call resets it to userOPERATING-SYSTEM OPERATIONS  Interrupt driven by hardware  Software error or request creates exception or trap  Division by zero, request for operating system service  Other process problems include infinite loop, processes modifying each other or the operating system  Dual-mode operation allows OS to protect itself and other system components  User mode and kernel mode  Mode bit provided by hardware  Provides ability to distinguish when system is running user code or kernel code  Some instructions designated as privileged, only executable in kernel mode  System call changes mode to kernel, return from call resets it to user