Operating system A program that acts as an intermediary between a user of a computer and the
computer hardware
kernel is the one program running at all times on the computer.
bootstrap program is loaded at power-up or reboot
EPROM, generally known as firmware
Interrupt transfers control to the interrupt service routine generally, through the interrupt
vector, which contains the addresses of all the service routines
interrupt driven is an operating system
Interrupt Handling the operating system preserves the state of the CPU by storing registers and
the program counter
Main memory: only large storage media that the CPU can access directly
Secondary storage: extension of main memory that provides large nonvolatile storage capacity
Caching: copying information into faster storage system; main memory can be viewed as a cache
for secondary storage
Important principle, performed at many levels in a computer (in hardware, operating system,
software)
Multiprocessors systems growing in use and importance
Also known as parallel systems, tightly-coupled systems
Clustered Systems: Like multiprocessor systems, but multiple systems working together
Multiprogramming needed for efficiency
Timesharing (multitasking) is logical extension in which CPU switches jobs so frequently that
users can interact with each job while it is running, creating interactive computing
Dual-mode operation allows OS to protect itself and other system components
Mode bit provided by hardware
Process Management A process is a program in execution. It is a unit of work within the system.
Program is a passive entity, process is an active entity.
Mass-Storage Management Usually disks used to store data that does not fit in main memory or
data that must be kept for a “long” period of time
Migration of Integer A from Disk to Register
Multitasking environments must be careful to use most recent value, no matter where it is stored
in the storage hierarchy
Multiprocessor environment must provide cache coherency in hardware such that all CPUs have
the most recent value in their cache
Distributed environment situation even more complex
