CSCI 1302

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CSCI 1302

• Introduction to Operating Systems

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Motivation

• Maximize system utilization
• CPU
• Memory
• Efficiency
• Tasks should complete as soon as possible
• Security

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OS Placement
Applications (Word, IE, Games, etc.)
User
Low-level apps (compilers, interpreters, editors)
Operating System
Machine Language (Binary)
Machine
Microarchitecture (processor-level)
Physical Devices (Hardware)
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OS Defined

• Extended Machine
• Service provider for hardware
• Abstracts the details of the machine
• Provides an API (system calls) to user
• Resource Manager
• Multiple users, multiple resources
• Orderly, controlled allocation of resources
• Fairness, protection, space-time, etc.

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Single Processor Systems

• Batch processing
• Job queue
• First-in, first-out (FIFO)
• Interactive processing (real-time)
• Time-sharing
• Rapid swapping of tasks (multiple users)
• Multitasking
• Rapid swapping of tasks (single user)

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Multiprocessor Systems

• Move toward distributed (de-centralized)
  computing
• Information/resource sharing via networks
• Network of networks (Internet)
• Manage resources
• Distribute tasks (load balancing)
• Coordinating distributed communication

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Flavors of OS

• Mainframe
• Server
• Multiprocessor
• Personal Computer
• Real-Time
• Embedded
• Smart Card

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Mainframe OS

• High-end I/O capacity
• 1000 disks
• Gigabytes of data
• High-end web servers
• B2B (business to business) E-commerce
• High-speed VR/FMV Rendering
• Many small, simultaneous jobs

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Server OS

• Large personal computers
• Print, file servers for small businesses
• Web servers
• Can load balance these to increase performance
• UNIX, Linux, Win2k Win2003 Server OS

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Multiprocessor OS

• Connect multiple computers together
• Share/distribute jobs among multiple
  machines/processors
• Specialized protocols for managing communication
• Win2000 Win2003 Advanced Server

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Personal Computer OS

• Focus on single user, multiple jobs
• What youre running on your machine
• Win9x, Win2000 Pro, Linux

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Real-Time OS

• Time dominates these machines specs
• Data collection from production lines, factory
  machinery
• Hard real-time time critical in all instances
• Soft real-time OK to drop occasionally

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Embedded OS

• Personal Digital Assistants
• TVs, microwaves, mobile phones
• Very small OS, embedded on chip
• PalmOS, WinCE

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Smart Card OS

• Credit card sized devices
• Specialized OS for specialized purposes
• E-payment cards (e-cash cards)
• Some JVM coming into play

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Hardware Review
CPU
Memory
Display
Display Controller
Bus
Keyboard
Keyboard Controller
Floppy
Floppy Controller
Hard Disk
Hard Disk Controller
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Hardware Review

• Processors
• Memory
• I/O Devices
• Bus

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Processors

• Brain of the computer
• Fetch, decode, execute cycle
• Registers
• Program Counter (PC)
• Stack Pointer (SP)
• Pipelining improves performance, but complexities
  of rolling back appear
• Kernel vs. User Mode (enables establishing
  limitations of instruction set available)

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Memory

• Trade off of speed vs. cost/size
• Registers (on processor)
• Cache (processor)
• Cache (mainboard)
• Main Memory
• Disk
• Other Network Cache/Machines
• Tape

Cost increases
Speed decreases
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I/O Devices

• Typically consist of two parts
• Controller
• Device
• Controller manages presents the API of the
  device to the OS
• The software that talks to the controller is
  called a device driver

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Memory Allocation

• We need a protective and fair way of allocating
  and resizing memory blocks for processes/jobs
• Two sections of memory
• Code (typically static)
• Data (volatile)

Limit
User 2 Data
Base
Limit
User 1 Data
Base
Limit
Program Code
Base
OS
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Computer Memory

• The CPU is often referred to as the brain of the
  computer. This is where all the actual computing
  is done.
• The chipset supports the CPU. It usually contains
  several "controllers" which govern how
  information travels between the processor and
  other components in the system. Some systems have
  more than one chipset.

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Computer Memory

• The memory controller is part of the chipset, and
  this controller establishes the information flow
  between memory and the CPU.
• A bus is a data path in a computer, consisting of
  various parallel wires to which the CPU, memory,
  and all input/output devices are connected.
• The memory bus runs from the memory controller to
  the computer's memory sockets

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Computer Memory

• Memory speed is sometimes measured in Megahertz
  (MHz), or in terms of access time - the actual
  time required to deliver data - measured in
  nanoseconds (ns).
• A computer's system clock resides on the
  motherboard. It sends out a signal to all other
  computer components in rhythm, like a metronome.
• Cache memory is a relatively small amount
  (normally less than 1MB) of high speed memory
  that resides very close to the CPU. Cache memory
  is designed to supply the CPU with the most
  frequently requested data and instructions.

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Invoking Device Actions

• Busy wait execute a kernel-level system call
  and wait (ties up the processor ?)
• Ask the device to generate an interrupt (signal
  that its done or failed)
• Doesnt tie up the processor
• Adds complexity
• DMA Direct Memory Access
• Bypasses the use of the processor
• Allows the device to write directly to memory
  once the rules of the road are established

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Bus

• Communication highway for all data to travel
  upon
• Multiple buses exist in modern machines
• Cache (fastest)
• Local (on mainboard other busses connect to it)
• Memory
• PCI (successor of ISA - high-speed I/O)
• SCSI (high-speed scanners disks)
• USB (slow peripherals)
• IDE (disks, etc.)
• ISA (slowest legacy)

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OS Architecture

• Application vs. System software
• Utility vs. OS
• Security, adaptability, customization (OO)
• Shell
• Interface to user (text or GUI)
• Kernel
• Core of the OS (file mgr, device drivers, memory
  mgr, scheduler)

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Bootstrapping (booting)

• ROM (BIOS) read first
• Load OS into volatile memory
• Transfer control to OS code

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Processes

• Task
• Maintains state (process state)
• Program counter (PC)
• Register values
• Memory (process-scope)
• ProgramProcessClassObject

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Processes

• Defined as a program in execution
• AKA a job
• Contain
• Instructions (code segment)
• SP, PC, registers, file handles
• Data segment
• Processes can spawn subprocesses threads
• The OS must ensure fairness protection,
  timeslicing managing multiple processes at a
  time

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Process Internals

• States
• Running
• Ready
• Blocking
• Process Control Block
• State
• Registers Memory
• PC, SP, Files

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Process Administration

• Coordinating competing processes
• Scheduler
• Process table (lists all processes)
• Process state priorities
• Dispatcher
• Time slice (quantum)
• Process/context switch
• Generate interrupt (interrupt handler)

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FIN