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1.1 What is an operating system

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Hides the messy details which must be performed. Presents user with a virtual machine, easier ... Unix: several shells (e.g. csh, ksh). MSDOS: command prompt. ... – PowerPoint PPT presentation

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Title: 1.1 What is an operating system


1
Introduction
  • Chapter 1

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
2
Introduction
  • A computer system consists of
  • hardware
  • system programs
  • application programs

3
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

4
History of Operating Systems (1)
  • 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

5
History of Operating Systems (2)
  • 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

6
History of Operating Systems (3)
  • Structure of a typical FMS job 2nd generation

7
History of Operating Systems (4)
  • Multiprogramming system
  • three jobs in memory 3rd generation

8
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

9
Computer Hardware Review (1)
Monitor
Bus
  • Components of a simple personal computer

10
Computer Hardware Review (2)
  • (a) A three-stage pipeline
  • (b) A superscalar CPU

11
Computer Hardware Review (3)
  • Typical memory hierarchy
  • numbers shown are rough approximations

12
Computer Hardware Review (4)
  • Structure of a disk drive

13
Computer Hardware Review (5)
  • One base-limit pair and two base-limit pairs

14
Computer Hardware Review (6)
(a)
(b)
  • (a) Steps in starting an I/O device and getting
    interrupt
  • (b) How the CPU is interrupted

15
Computer Hardware Review (7)
  • Structure of a large Pentium system

16
Operating System Concepts (1) - Processes
  • A process is a program in execution
  • Swapping of a process Process table entry
  • System calls to create and terminate processes
  • System calls to allocate/deallocate memory
  • System calls for communication - signals

17
Operating System Concepts (2) - Processes
  • A process tree
  • A created two child processes, B and C
  • B created three child processes, D, E, and F

18
Operating System Concepts (3) -Deadlocks
  • (a) A potential deadlock. (b) an actual deadlock.

19
Operating System Concepts (4) - Files
  • Present the programmer with nice, clean,
    abstract, device-independent files.
  • Concept of directory to group files together
  • System calls to create/remove directories and
    create/remove files. Hierarchies.
  • Process trees ! Directories
  • A file can be specified by a path name absolute
    (from root), relative (from current working
    directory).

20
Operating System Concepts (5) - Files
  • File system for a university department

21
Operating System Concepts (6) - Files
  • Protection of files and directories, e.g. UNIX
    the rwx bits 9 bits (owner/group/others)
    rwxr-xr--
  • File Descriptor a number assigned to a file.
  • Mounting file systems.
  • Special files block special files, character
    special files standard input (fd0), standard
    output (fd1), standard error (fd2).

22
Operating System Concepts (7) - Files
  • Before mounting,
  • files on floppy are inaccessible
  • After mounting floppy on b,
  • files on floppy are part of file hierarchy

23
Operating System Concepts (8) - Pipes
  • Two processes connected by a pipe. Read/Write -
    transparent for processes.

24
Operating System Concepts (8) - Shell
  • The shell is a program that acts as an interface
    between the user and the OS.
  • Unix several shells (e.g. csh, ksh).
  • MSDOS command prompt.
  • Prompt, process, std input, output, creates
    processes.

25
Steps in Making a System Call
  • There are 11 steps in making the system call
  • read (fd, buffer, nbytes)

26
Some System Calls For Process Management
27
Some System Calls For File Management
28
Some System Calls For Directory Management
29
Some System Calls For Miscellaneous Tasks
30
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 /

31
System Calls (2)
  • Processes have three segments text, data, stack

32
System Calls (3)
  • (a) Two directories before linking/usr/jim/memo
    to ast's directory
  • (b) The same directories after linking

33
System Calls (4)
  • (a) File system before the mount
  • (b) File system after the mount

34
System Calls (5)
  • Some Win32 API calls

35
Operating System Structure
  • Monolithic
  • Layered
  • Virtual Machines
  • Client-Server

36
Operating System Structure (1)
User program 1
User program 2
Kernel call
4
1
Service procedure
3
2
dispatch table
37
Operating System Structure (1)
  • Simple structuring model for a monolithic system

38
Operating System Structure (2)
  • Structure of the THE operating system

39
Operating System Structure (3)
  • Structure of VM/370 with CMS

40
Operating System Structure (4)
  • The client-server model

41
Operating System Structure (5)
  • The client-server model in a distributed system

42
Metric Units
The metric prefixes
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