COP 4610
Operating systemsModule1
Introduction to Operating System Concepts
PART I
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Module 1 - OPERATING SYSTEMS CONCEPTS
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What Operating Systems Do
Computer-System Organization
Operating-System Operation
Defintions
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What is an operating system?
A program that acts as an intermediary between a user of a computer and the computer hardware
Operating system goals:
◦ Execute user programs
◦ Make solving user problems easier
◦ Make the computer system convenient to use
◦ Use the computer hardware and resources in an efficient manner
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What do Operating Systems do?
User view
◦ Extended machine that hides lower level details
System view◦ Resource allocator
◦ (What is a resource?)
OS is a manger that needs to use all the resources to perform management duties
◦ Overhead
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Definitions Resource -
◦ Component of limited availability necessary for effective operation
Process –
◦ Program in execution
◦ Active program
Deadlock -
◦ A situation in which two or more competing actions are each
waiting for the other to finish, and thus neither ever does.
Buffer –
◦ Area of memory that stores data
Cache –
◦ Area of fast memory that stores copies of data
What is the difference between a buffer and a cache?
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Definitions OS kernel –◦ Contains basic functions (one process
all the time)
◦ Everything else is either a system program (ships with the operating system) or an application program.
Interrupt -◦ Change in flow of execution
◦ Operating systems are
interrupt driven
Volatile storage –
Persistent/ Nonvolatile storage–
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running active
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Computer system organization One or more CPUs, device controllers connect through
common bus providing access to shared memory
Concurrent execution of CPUs and devices competing for memory cycles
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Computer-System Operation I/O devices and the CPU can execute
concurrently
Each device controller is in charge of a particular device type
Each device controller has a local buffer
CPU moves data from/to main memory to/from local buffers
I/O is from the device to local buffer of controller
Device controller informs CPU that it has finished its operation by causing an interrupt
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Common Functions of Interrupts
Interrupt transfers control to the interrupt service routine
Interrupt architecture must save the address of the interrupted instruction
A trap or exception is a software-generated interrupt caused either by an error or a user request
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COP 4610
Operating systemsModule 1
More Operating System Concepts
PART II
10Tami Sorgente
Module 1 –OPERATING SYSTEMS CONCEPTS
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Multiprocessor vs multiprogramming
Operating-System Componentso Process Management
o Memory Management
o Storage Management
o Protection and Security
System calls
Computing
Environments
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Multiprocessing
Single-processor systems
Multiprocessor systems
◦ Increased throughput
◦ Economy of scale (cost less share resources)
◦ Increased reliability
Asymmetric vs symmetric multiprocessing
Multiprocessor vs clustered systems
Multiprocessing vs multiprogramming
◦ Degree of multiprogramming
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OS system structure
Multiprogramming
◦ keep CPU and I/O devices busy at all times
Timesharing/ multitasking
◦ Each user has at least one program executing in memory
◦ If several jobs ready to run at the same time CPU scheduling
◦ If processes don’t fit
in memory, swapping
moves them in and
out to run
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Components of an OS
Process management
Memory management Storage management ◦ Uniform, logical view of information storage
◦ File management
◦ I/O subsystem (hide peculiarities of hardware devices from the user)
Networking
Protection and Security◦ Protection- any mechanism for controlling access of processes
or users to resources defined by the OS
◦ Security - defense of the system against internal and external attacks
User interface14Tami Sorgente
System calls
System call
◦ Method used by a process to request an action by
the OS
Dual mode operation
◦ 2 modes: user and
supervisor/privileged/monitor/kernel
◦ Privileged instructions must go through the OS
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Types of system calls
Process control
File management
Device management
Information maintenance
Communications
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Computing environments
Traditional
Mobile
Distributed Local Area Network (LAN) – room, building, campus
Wide Area Network (WAN) – cities, countries
Metropolitan Area Network (MAN) – buildings in a city
Personal Area Network (PAN) – (i.e. Bluetooth)
Network Operating System
◦ Systems across network
◦ Illusion of a single system
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Computing environments
Cloud Computing◦ Public cloud –anyone willing to pay
◦ Private cloud –company’s own use
◦ Hybrid cloud –both public and private components
◦ Software as a Service (SaaS) – one or more applications available via the Internet (i.e. word processor)
◦ Platform as a Service (PaaS) – software stack ready for application use via the Internet (i.e a database server)
◦ Infrastructure as a Service (IaaS) – servers or storage available over Internet (i.e. storage available for backup use)
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Multiprocessor Early systems allow only one process to run, others
suspended
Due to screen real estate, UI limits iOS provides for a ◦ Single foreground process- controlled via user interface
◦ Multiple background processes– in memory, running, but not on the display, and with limits
◦ Limits include single, short task, receiving notification of events, specific long-running tasks like audio playback
Android runs foreground and background, with fewer limits◦ Background process uses a service to perform tasks
◦ Service can keep running even if background process is suspended
◦ Service has no user interface, small memory use
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Multiprocess Architecture – Chrome Browser
Many web browsers ran as single process (some still do)
◦ If one web site causes trouble, entire browser can hang or crash
Google Chrome Browser is a multiprocess with 3 categories
◦ Browser process manages user interface, disk and network I/O
◦ Renderer process renders web pages, deals with HTML,
Javascript, new one for each website opened
Runs in sandbox restricting disk and network I/O,
Minimizing effect of security exploits
◦ Plug-in process for each type of plug-in
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