Operating System Concepts Ch. 1

Operating System

Program that manages computer hardware

Hardware

CPU, Memory, I/O devices which provide basic computing resources for the system

Central Processing Unit (CPU)

Main Processor

Memory

Dynamic data storage unit

Input/Output devices

devices that are used to input to a computer (keyboard, mouse) or output (monitor)

Application Programs

Word processors, spreadsheets, compilers, and web browsers

Ease of Use

how convenient it is for a user to use a PC

Resource Utilization

how various hardware and software resources are shared

Mainframe

large and powerful data processing system

Minicomputer

Middle range of computing systems, between mainframes and PCs

Workstation

a work PC

resource allocator

job of the operating system, allocates and manages hardware resources

Control Program

manages the execution of user programs to prevent errors and improper use of the computer

bit

basic unit of computer storage (0 or 1)

byte

8 bits, smallest convenient chunk of storage

Word

a given computer architectures native storage unit (made up of one or more bytes)

Kernel

the one program running at all times on the computer

Systems program

associated with the OS but not part of the kernel

Bootstrap program

automatic procedure whereby basic OS is reloaded following a complete shutdown or loss of memory

Read-only memory (ROM)

read only memory

EEPROM

electrically erasable programable read only memory

firmware

same thing as EEPROM

Interrupt

signal sent from hardware or software to CPU to transfer execution to some other instructions

System Call

software interrupt

Random Access Memory (RAM)

main memory, called random access memory

Von Neumann Architecture

Typical instruction-execution cycle where instructions are fetched from memory and stored in the instruction register

Instruction Register

Used to hold the current instruction that is being executed

secondary storage

extension of main memory where large quantities of data can be held permanently

Magnetic Disk

provides storage for both programs and data

Volatile storage

loses its contents when power to the device is removed

Nonvolatile storage

storage that does not lose its contents when power is removed

Electronic Disk

can be either volatile or nonvolatile, it stores data in large DRAM array

NVRAM

nonvolatile storage which is DRAM with battery backup power

Small computer-Systems Interface (SCSI)

a controller that can provide connection to 7 or more devices to move data between peripheral devices and local buffer storage

Device Driver

Understands device controller and presents a uniform interface to the device to the rest of the OS

Direct Memory Access (DMA)

When a device controller transfers an entire block of data from its own buffer storage to memory without CPU intervention

Single-Processor System

systems that have only one main CPU

Multi-processor system

parallel systems that have more than one processor in close communication

Graceful Degradation

Ability to continue providing service proportional to the level of surviving hardware

Fault Tolerant

can suffer a failure of any single component and still continue operation

Asymmetric Multiprocessing

each processor is assigned specific tasks by a "Master processor"

Symmetric Multiprocessing (SMP)

each processor performs all tasks within the OS, processors are peers, there are no peers

Uniform Memory Access (UMA)

uniform memory access, in which access to any RAM from any CPU takes the same amount of time

Non-Uniform Memory Access (NUMA)

non uniform memory access, in which some parts of memory take longer to access than other parts

Computer Core

multiprocessor chips, can be more efficient than multiple chips with single cores because on-chip communication is faster than between-chip communication

Clustered System

composed of two or more individual systems or odes joined together over a LAN or faster interconnect (Infiniband)

High-Availability Service

service continues even if one or more systems in the cluster fail

Asymmetric Clustering

one machine is in hot-standby mode while the other is running applications

Symmetric Mode (in clustering)

two ore more hosts are running applications and monitoring each other

High-Performance computing

supply significantly greater computational power than a single-processor or even SMP systems because they are capable of running an application concurrently on all computers in the cluster

Parallelization

consist of dividing a program into separate components that run in parallel on individual computers in the cluster

Distributed Lock Manager

to provide shared access to data, system must supply access control and locking to ensure that no conflicting operations occur

Multiprogramming

increases CPU utilization by organizing jobs (code and data) so that the cpu always has one to execute

Job Pool

consists of all processes residing on disk awaiting allocation of main memory

Time Sharing

cpu executes multiple jobs by switching among them, but the switches occur so frequently that the users can interact with each program while its occuring

Interactive Computer System

provides direct communication between the user and the system

Response Time

time it takes for the computer to give results

Process

a program loaded into memory and executing

Job Scheduling

if several jobs are ready to be brought into memory and if there is not enough room for all of them - system must choose among them

CPU Scheduling

if several jobs are ready to run at the same time, the system must choose among them

Swapping

processes are swapped in and out of main memory to the disk

Virtual Memory

a technique that allows the execution of a process that is not completely in memory

Trap

software - generate interrupt caused either by an error (divide by 0 or invalid memory access) or by a specific request from a user program that an operating-system service be performed

Dual mode operation

hardware support that allows us to differentiate amount various mods of execution (user defined code vs. os code)

User Mode

when the computer is executing on behalf of a user application

Kernel Mode

when a user application requests a service from the operation system

Mode Bit

bit added to the hardware of the computer to indicate the current mode: kernel(0) or user (1). Distinguishes between a task that is executed on behalf of the OS and one is that executed on behalf of the user

Privileged Instruction

A computer instruction that can be executed only by a supervisory program - can only be executed only in kernel mode

Timer interrupt

interrupts the computer after a specified period

Variable Timer

generally implemented by a fixed-rate clock and counter - from 1 millisecond to 1 second; random amount of time

Tertiary Storage

type of computer storage device that typically consists of magnetic tape (HDD, etc. )

Caching

storing data in a cache memory

Cache Management

Makes sure that the cache size and replacement policy can result in greatly increased performance

Cache Coherency

Makes sure that an update of a value of A in one cache is immediately reflected in all other caches where A resides

Protection

any mechanism for controlling the access of processes or users to the resource defined by a computer system

Security

defends a system from external and internal attacks

User ID

list of usernames

Group ID

group functionality that can be implemented as a system-wide list of group names

Escalate Privileges

changing privileges to gain extra permissions for an activity

Effective User ID

user id with extra privileges

Network

a communication path between two or more systems

Local-Area Network (LAN)

connects computer within a room, a floor or building

Wide-Area Network (WAN)

network that usually links buildings, cities, or countries

Network operating system

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

Real-Time operating system

an OS intended for real time applications --> almost always used in embedded systems

Handheld system

include personal digital assistants, cell phones, etc

Client System

A computer used to access the maestro HUB or LUI components --> connected to a server system/is a branch of it

Server System

a data processing system containing one or more servers providing services in response to a request from another computer

Compute-Server System

provides an interface to which a client can send a request to perform an action --> server executes the action sends back results to the client

file-server system

provides a file-system interface where clients can create, update, read and delete files

Load Balancers

distribute network connections amount a pool of similar servers

Open-Source operating systems

OS's made available in source-code format rather than as compiled binary code

Closed-Source

made available as compiled binary code

Free Software Foundation (FSF)

encourages the free exchange of software source code and the free use of software

GNU General Public License (GPL)

codifies copylefting and is a common license under which free software is released. Requires that the source code by distributed with any binaries and that any changes made to the source code be released under the same GPL license

GNU/Linux

example of an open-source operating system (produced many UNIX-compatible tools, including compilers, editors, and utilities - never released a kernel)

BSD Unix

started in 1978 as a derivative of AT&T's unix

Solaris

commercial UNIX-based operating system of Sun Microsystems

Temporal Locality

program is likely to access data it has accessed recently (stored locally for quick and recent use)

Spatial Locality

program is likely to access data nearby to what it has accessed recently (stored in data segment elsewhere)