CS370 Chapter 1

Components of the I/O subsystem

-A memory-management component that includes buffering, caching, and spooling. -A general device-driver interface -Drivers for specific hardware devices

4 components of a computer system

-Hardware -Operating System -Applications -Users

Advantages of multiprocessor systems

-Increased throughput (more work less time) -Economy of scale -Increased reliability

Attributes of main memory

-Usually too SMALL -VOLATILE storage device; loses its contents when power is turned off.

Asymmetric multiprocessing

A master processor controls the system; the other processors either look to the master for instruction or have predefined tasks. Master-slave relationship.

Operating System

A program that manages the computer hardware. Acts as an intermediary between the user and the hardware.

Process

A unit of work in a system.

Random-access memory

AKA Main memory; rewritable memory.

Network operating system

An OS that provides features such as file sharing across the network and that includes a communication scheme that allows different processes on different computers to exchange messages.

Interrupt vector

Array of addresses indexed by a unique device number, given by the interrupt request, to provide the address of the interrupt service routine for the interrupting device.

Time sharing system

CPU executes multiple jobs by switching among them, but the switches occur so frequently that the users can interact with each program while it is running. Allows many users to share the computer simultaneously. Each user is given the impression that the entire computer system is dedicated to his/her use.

A general purpose computer system consists of:

CPUs and multiple device controllers that are connected through a common bus.

Local-area network (LAN)

Connects computers withing a room, a floor, or a building.

Job pool

Consists of all processes residing on disk awaiting allocation of main memory.

***parallelization

Consists of dividing a program into separate components that run in parallel on individual computers in the cluster. Typically implemented so that once each computing node in the cluster has solved its portion of the problem, the results from all the nodes are combined into a final solution.

Symmetric multiprocessing (SMP)

Each processor performs all tasks within OS. All processors are peers; no master-slave relationship.

User mode

Executing on behalf of a user application. Mode bit = 1

Secondary storage

Extension of main memory; must be able to hold large quantities of data permanently.

Clustered System

Gather together multiple CPUs to accomplish computational work. Composed of two or more individual systems. Clustered computers share storage and are closely linked via a local-area network(LAN).

I/O subsystem

Hides the peculiarities of I/O devices from the bulk of the OS.

***high-performance computing environments

Higher computational power than single-processor or SMP systems.

Multiprogramming

Increases CPU utilization by organizing jobs so that the CPU always has one to execute.

Kernel mode

Necessary to fulfill services from the operating system. Mode bit = 0

Single-processor system

One general-purpose CPU.

***asymmetric clustering

One machine is in hot-standby mode while the other is running the applications. Hot-standby machine becomes active server if the server fails.

***interactive computer system

Required by time-sharing system; provides direct communication between the user and the system.

Small-area network (SAN)

Several feet, found in homes.

Interrupt

Signals the occurrence of an event from either the hardware of the software, usually by way of the system bus.

Program counter

Specifies the next instruction to execute.

Caching

Storage system that is fast and used on a temporary basis. Information in the cache is assumed to be needed again soon.

Bootstrap program

The initial program to be run on startup. Generally stored in ROM (read-only memory) or EEPROM. It must locate and load into memory the operating system kernel.

Kernel

The operating system is the one program running at all times on the computer.

Main purpose of operating system

To get out of the way of the user and facilitate work to be done. Similar to the role of a government: provides an environment for other programs to do useful work.

System Call

Triggers an interrupt

***symmetric mode

Two or more hosts are running apps and monitor each other. This is MORE EFFICIENT.

Multi-processor systems

Two or more processors in close communication, sharing the computer bus and sometimes the clock, memory, and peripheral devices.

Real-time operating systems

Used when rigid time requirements have been placed on the operation of a processor of the flow of data. Well-defined, fixed time constraints. Processing must be done within the time constraints or the system will fail.

Wide-area network (WAN)

Usually links buildings, cities, or countries.

Network

a communication path between two or more systems.