Transcript 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
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Introduction to Information Technologies
Modern computer architecture
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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
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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
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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)
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Introduction to Information Technologies
Time sharing the CPU
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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.
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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
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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
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Introduction to Information Technologies
Secondary storage management
(7/10)
• Functions:
– optimizes I/O (concurrent)
– Reorder requests for efficient disk usage
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Introduction to Information Technologies
Security (8/10)
• Protect users and programs
• Users: privileges, protection
• Programs: memory access, system services
access
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Introduction to Information Technologies
Network services (9/10)
• Networking facilities
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Introduction to Information Technologies
System Administration (10/10)
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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
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Introduction to Information Technologies
Bootstrapping
Memory Adress 0000
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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
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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.
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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
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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
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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
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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
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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
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Introduction to Information Technologies
Data packet format
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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
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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
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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
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Introduction to Information Technologies
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Introduction to Information Technologies
Ring
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Introduction to Information Technologies
Star
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Introduction to Information Technologies
Web
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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