Download ITEC 1000 Introduction to Information Technologies

Operating Systems
ITEC 1000
Introduction to Information Technologies
Introduction
• OS goals:
– Control/manage the hw
– Offer the user and programs access to specific
services
• OS expands computer capabilities
– Support for multiple programs, users
– Connect to other computers
• Many types of Oses
• Most complex and dynamic computer
component
ITEC 1000
Introduction to Information Technologies
Critique of the LMC
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Program was supposed to be in the memory
No clear way to start programs
No user interface
Cannot stop a running program
One program at a time
No possibility for users to control the
computer (load, execute programs, network)
ITEC 1000
Introduction to Information Technologies
The OS Concept
• OS = computer program, that:
– Integrates the hw resources
– Makes the hw resources available to other programs
and users
– Such that the user has access to the computer in a
productive, timely and efficient manner
• Services:
– Accept and execute commands/requests from users and
programs
– Manage, load, execute programs
– Manage the hw resources
ITEC 1000
Introduction to Information Technologies
User
APP
O.S
Hw
ITEC 1000
Introduction to Information Technologies
Modern computer architecture
ITEC 1000
Introduction to Information Technologies
OS as a program manager
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Bootstrapping
User interface
File support services
I/O services
Interrupt processing
Network services
Concurrent processing
Resource allocation
Security
System administration
ITEC 1000
Introduction to Information Technologies
OS Services
ITEC 1000
Introduction to Information Technologies
OS Features
• Components:
– Resident part = kernel
– Non-resident
• Types
– User: single - multiple
– Task: single – multiple
ITEC 1000
Introduction to Information Technologies
Events
• OS is event driven
• Events originate from:
– Interrupts
– Service requests
• Portability – same OS for many types of hw
• Ex: Unix
ITEC 1000
Introduction to Information Technologies
Basic single job OS – MS DOS
• MS-DOS – best known single task OS
• Memory resident components
– Command interface
– I/O routines
– File management system
• Typical loop
– Print C:>
– Read command
– Process command
ITEC 1000
Introduction to Information Technologies
MS-DOS memory map
ITEC 1000
Introduction to Information Technologies
Concurrent operations
• Single job processing – wastes system
resources
• Solution: multitasking/multiprogramming
• Multitasking OS:
– Can be single or multiple user
– Must allocate resources efficiently and fairly
(CPU, memory, I/O devices)
– Only one program can use the CPU at a time
• Share CPU during I/O waiting
• Share CPU by using clock interrupts
ITEC 1000
Introduction to Information Technologies
Dispatching
• Dispatching = selecting next program to run
• In addition to Dispatching, OS must:
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Keep track of programs
Manage memory
Schedule I/O
Save/restore program status
Manage/control overall performance
Introduction to Information Technologies
Concurrent operations
• OS gets control by:
– Interrupt
– Service requests
• Special hardware support for OS
– Memory management
– Protection mechanisms
ITEC 1000
Introduction to Information Technologies
Sharing the CPU (during I/O breaks)
ITEC 1000
Introduction to Information Technologies
Time sharing the CPU
ITEC 1000
Introduction to Information Technologies
Services and facilities
• Monitor/supervisor – handles competing
requests
ITEC 1000
Introduction to Information Technologies
User interface (1/10)
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Most visible to users
Some consider it separated from the OS
Types: GUI and CLI
Most often used commands: file operations,
program loading and execution
• Commands: built in directly (resident) and
non-resident
• Scripts: JCL, BAT, shell scripts
ITEC 1000
Introduction to Information Technologies
File management (2/10)
• File: collection of related data
– Logical unit of storage
– Has also a physical representation/location
• File manipulation:
– Independent of the device
– Based on directories and file names
• Functionality:
– Keep directory structure, offer tools for manipulating
them
– Tools for manipulating files
– Information about files
– security
ITEC 1000
Introduction to Information Technologies
I/O Services (3/10)
• Interrupt handlers = device drivers
• Types of device drivers: in memory, on disk
• Installing device drivers:
– Automatic (MAC)
– Plug-and-play (Windows)
• 7 and 8 not that much.
ITEC 1000
Introduction to Information Technologies
Process control management
• Every program is treated as a process
• Inter-process messaging services
• Functionality:
– Keep track of processes
– Coordinate messaging, synchronization
• Smaller units: threads
ITEC 1000
Introduction to Information Technologies
Memory management (5/10)
Word
Power point
• Functions:
Chrome
– Keep track of memory
– Keep track of programs to be loaded
– Allocate/de-allocate memory
Word
Chrome
ITEC 1000
Introduction to Information Technologies
Memory Management (cont)
• Virtual memory
• Tentative to Run Explorer (Needs 4M)
Word
Power point
It doesn’t Fit
Chrome
Free Memory = 1M bytes
Word
Explorer
HD
Transfer to Virtual Memory
Chrome
ITEC 1000
Introduction to Information Technologies
Ppt
Scheduling (6/10)
• Levels:
– High: which jobs to be scheduled and in what order
– Low: dispatching: select next job to use the CPU
• Types of processes: CPU bound and I/O bound
• Context switching
• Types of dispatching
– Preemptive: use the clock interrupts
– Non-preemptive: only if blocked by I/O or gives
control
ITEC 1000
Introduction to Information Technologies
Secondary storage management
(7/10)
• Functions:
– optimizes I/O (concurrent)
– Reorder requests for efficient disk usage
ITEC 1000
Introduction to Information Technologies
Security (8/10)
• Protect users and programs
• Users: privileges, protection
• Programs: memory access, system services
access
ITEC 1000
Introduction to Information Technologies
Network services (9/10)
• Networking facilities
ITEC 1000
Introduction to Information Technologies
System Administration (10/10)
• Functions:
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System configuration
User management
Security monitoring
Backups
Mounting/un-mounting file systems
Upgrade, install new software
Recover lost data
Statistical information
Introduction to Information Technologies
Organization of the OS
• Monolithic - Unix
ITEC 1000
Introduction to Information Technologies
Bootstrapping
Memory Adress 0000
ITEC 1000
Introduction to Information Technologies
Why Connect Computers? (Chapter 11)
Remote (shared) access to information & data
Share resources such as printers
Access to more powerful or larger resources
Increased system reliability: fault tolerance increased
Increased computational power: eg distributed processing
ITEC 1000
Introduction to Information Technologies
Types of coupling
Loosely Coupled Systems: (multicomputer systems)
Each computer mostly independent: has own memory,
CPU, and I/O facilities.
Tightly coupled systems: (multiprocessor systems)
Share some or all of memory and I/O resources.
ITEC 1000
Introduction to Information Technologies
Communication channels
• Path over which data moves
• Is treated like a standard I/O device by the
OS
• Uses a network card and an I/O driver
• Allows to share: files, data, messages,
programs (CORBA, RMI, DCOM)
• Data moves from the memory of one
computer to the memory of another
computer
ITEC 1000
Introduction to Information Technologies
Configurations for loosely connected computers
• Direct transmission (point-to-point) (p2p)
– Ex: modems and phone lines
– Ex: serial I/O ports
– Ex: AOL and other dial-up systems
• Shared communication
– Multipoint/multidrop channel
– LAN
ITEC 1000
Introduction to Information Technologies
An example of point-to-point connectivity
ITEC 1000
Introduction to Information Technologies
Communication terminology
• Characteristics: speed, medium/cable,
rules/protocol
• Communication standards
• Network topology: the way computers are
interconnected
• Client-server:
– Server (who): provide services (what)
– Client: use the server to gain access to services
ITEC 1000
Introduction to Information Technologies
Requirements
• CPU < - - - > network : treated as I/O
• Data/programs to be sent over the network
must be stored (at both ends) in the memory
• Common format/standard/protocol for
transmission
ITEC 1000
Introduction to Information Technologies
Transmission protocols and
formats
• Requirements:
– Standard message formats (length,
headers/footers, error detection, completeness,
reassembling from parts)
• Open system: can communicate with other
systems at all levels
ITEC 1000
Introduction to Information Technologies
Protocol
• Standard set of communication rules
• Works as set of protocols (separation of tasks)
• Defines data transmission formats (bits to
packages).
• Advantages of packages
– Reduced overhead by sending arrays of bytes
– Unit for data routing (from network to network)
– Alternative to exclusive use of channels (channels can
be used for multiple transmissions)
– Receiver can process the whole block of data at once
– Simplified synchronization
ITEC 1000
Introduction to Information Technologies
Data packet format
ITEC 1000
Introduction to Information Technologies
Open Systems Interconnection
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7 layered protocol: each has well defined functions
Application: specific utilities and tools
Presentation: conversion between standards
Session: the whole dialog between client and server
Transport: reliability of end-to-end transmission; made
of routers
Network: addressing and message routing
Data link: transmits packs of bytes called frames;
responsible for frames transmission reliability
Physical layer – the medium; implemented by the
hardware; transmits bare bits
Introduction to Information Technologies
OSI Layers
ITEC 1000
Introduction to Information Technologies
TCP/IP
Transmission Control
Protocol/Internet Protocol
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One of many protocols
Most widespread
Associated with Unix
Guarantees delivery
ITEC 1000
Introduction to Information Technologies
TCP/IP
• IP = network layer
– Packet = datagram < 65k bytes
– Uses routing
• TCP = transport layer
• Application layer: Telnet, FTP, HTTP,
SMTP, Finger
ITEC 1000
Introduction to Information Technologies
Local area Networks
• Over small areas
• Configuration = topology
• Not possible to have p2p between all
computers
• Practical topologies:
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Bus
Ring
Star
Web
Introduction to Information Technologies
Bus
ITEC 1000
Introduction to Information Technologies
ITEC 1000
Introduction to Information Technologies
Ring
ITEC 1000
Introduction to Information Technologies
Star
ITEC 1000
Introduction to Information Technologies
Web
ITEC 1000
Introduction to Information Technologies
LAN Protocols
• Ethernet
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Based on the bus topology
Messages are sent in frames
Ideal for light traffic
Significant probability of collision
ITEC 1000
Introduction to Information Technologies
LAN Protocols
• Token ring
– Uses a token
(passed token) to
access the network
– No collisions
– For high traffic
Has the Token
ITEC 1000
Introduction to Information Technologies
Wide Area Networks
• Internet
• No simple topology
• Uses switched communication networks
ITEC 1000
Introduction to Information Technologies