CS530 Operating Systems

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CS530 Operating Systems
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Chap 1. Introduction

• 1.1 What is an operating system
• 1.2 History of operating systems
• 1.3 The operating system zoo
• 1.4 Computer hardware review
• 1.5 Operating system concepts
• 1.6 System calls
• 1.7 Operating system structure

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Introduction

• A computer system consists of
• hardware
• system programs
• application programs

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What is an Operating System

• It is an extended machine
• Hides the messy details which must be performed
• Presents user with a virtual machine, easier to
  use
• It is a resource manager
• Each program gets time with the resource
• Each program gets space on the resource

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Why DO We Study OS?

• to make a better OS
• to understand computer systems better.
• We are all computer users !!
• the capstone of all the computer science
  principles
• languages, hardware, data structures, algorithms.
  ,,,

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What Do We Study?

• Abstraction
• OS gives us an illusion that there are infinite
  number of CPUs, infinite memory, single world
  wide computing, ....
• System Design
• tradeoffs between performance and simplicity
• functionality either by hardware or by software
• How computers work
• let's look inside of computers
• OS Research

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Why do we study history?

• 1. Main focus
• Effect of changes in hardware technologies,
  computer usage, and cost on the design of OS
• 2. Hardware changes
• 1980 2000 factor
• MIPS 1 1000 1000
• cost/MIPS 100K 5 20000
• memory 128KB 1GB 8000
• disk 10MB 100GB 1000
• network 9600BPS 1GBPS 100000
• address bits 16bits 64bits 4 (24)

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History of Operating Systems (1)

• Early batch system
• bring cards to 1401
• read cards to tape
• put tape on 7094 which does computing
• put tape on 1401 which prints output

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History of Operating Systems (2)

• First generation 1945 - 1955
• vacuum tubes, plug boards
• Second generation 1955 - 1965
• transistors, batch systems
• Third generation 1965 1980
• ICs and multiprogramming
• Fourth generation 1980 present
• personal computers

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History of Operating Systems (3)

• Structure of a typical FMS job 2nd generation

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History of Operating Systems (4)

• Multiprogramming system
• three jobs in memory 3rd generation
• Hardware was very expensive

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History of Operating Systems (5)

• When hardware is cheap and humans are expensive
• Interactive timesharing
• Use cheap terminals to let multiple users
  interact with the system at the same time.
• Sacrifice CPU time to get better response time
  for users.
• Personal computing
• Computers are cheap, so give everyone a computer.
• Initially, OS became subroutine library again,
  but since then, have added back in memory
  protection, multiprogramming, ..etc.

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Lessons from the history

• Have to change with changing technologies
• Situation today is much like it was in the late
  60's OS's of today are enormous, complex. (You
  may think about dinosaurs)
• small OS 100K lines
• big OS 10M lines
• Why OS's are getting complex?
• intelligence show off
• market demands more features
• Avoid complexity

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The Operating System Zoo

• Mainframe operating systems
• Server operating systems
• Multiprocessor operating systems
• Personal computer operating systems
• Real-time operating systems
• Embedded operating systems
• Smart card operating systems

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Computer Hardware Review (1)
Monitor
Bus

• Components of a simple personal computer

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Computer Hardware Review (2)

• (a) A three-stage pipeline
• (b) A superscalar CPU

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Computer Hardware Review (3)

• Typical memory hierarchy

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Computer Hardware Review (4)

• Structure of a disk drive

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Computer Hardware Review (5)

• program protection relocation

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Computer Hardware Review (6)
(b)
(a)

• (a) Steps in starting an I/O device and getting
  interrupt
• (b) How the CPU is interrupted

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Computer Hardware Review (7)

• Structure of a large Pentium system

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Hardware Supports for OS

• timer operation
• atomic synchronization operations
• memory protection, fast address translation (TLB)
• IO control and operations (DMA, IOP)
• interrupts and exceptions
• OS protection (kernel/user mode)
• protected instructions
• system calls
• partial completion of an instruction

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Operating System Concepts (1)

• A process tree
• A created two child processes, B and C
• B created three child processes, D, E, and F

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Operating System Concepts (2)

• (a) A potential deadlock. (b) an actual deadlock.

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Operating System Concepts (3)

• File system for a university department

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Operating System Concepts (4)

• Before mounting,
• files on floppy are inaccessible
• After mounting floppy on b,
• files on floppy are part of file hierarchy

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Operating System Concepts (5)

• Two processes connected by a pipe

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Steps in Making a System Call

• There are 11 steps for read (fd, buffer, nbytes)

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Some System Calls For Process Management
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Some System Calls For File Management
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Some System Calls For Directory Management
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Some System Calls For Miscellaneous Tasks
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System Calls (1)

• A stripped down shell
• while (TRUE) / repeat forever /
• type_prompt( ) / display prompt /
• read_command (command, parameters) / input
  from terminal /
• if (fork() ! 0) / fork off child process
  /
• / Parent code /
• waitpid( -1, status, 0) / wait for
  child to exit /
• else
• / Child code /
• execve (command, parameters, 0) / execute
  command /

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System Calls (2)

• Processes have three segments text, data, stack

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System Calls (3)

• (a) Two directories before linking/usr/jim/memo
  to ast's directory
• (b) The same directories after linking

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System Calls (4)

• (a) File system before the mount
• (b) File system after the mount

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The ls Command in Unix

• Steps in executing the command ls type to the
  shell

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System Calls (5)

• Some Win32 API calls

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The Win32 Application Programming Interface

• The Win32 API allows programs to run on almost
  all versions of Windows

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Environment Subsystems (1)

• Various routes taken to implement Win32 API
  function calls

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Operating System Structure (1)

• Simple structuring model for a monolithic system

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Operating System Structure (2)

• Structure of the THE operating system

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Operating System Structure (3)

• Structure of VM/370 with CMS

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Operating System Structure (4)

• The client-server model

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Operating System Structure (5)

• The client-server model in a distributed system

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OS Research

• Identification of a problem/phenomenon
• physical memories are small
• CPU is getting faster but IO is NOT that much
• applications change often but OS does NOT
• personal computing is popular
• Hypothesize a solution

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OS Research (2)

• Evaluate hypothesis
• Measure
• Measure
• Measure again
• Use real system if possible
• gather trace data
• instrument existing systems
• simulation
• analytical investigation
• isolate small components

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OS Research

• Draw conclusions
• use result to suggest new hypotheses
• compare results against other's results
• Toughest things
• there are not necessarily any right answers
• no one can tell you with certainty that you are
  right
• you are never done
• large system is difficult to understand