Operating System

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Operating System

• Paper Code MCA 311
• Course MCA 2nd Year,(3rd Semester)
• Faculty Mrs. Pooja Pandey.
• Mrs. Rama Chaudhary

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Current Technology
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Why Operating System ?

• Stand alone Computer .
• FOR WHAT ???

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Is an OS essential?

• Not Necessary
• If OS is not available, application code is
  responsible of conducting duty of OS( Memory
  Management, Resource Allocation etc)

• It is Good Approach to have OS,
• this will allow individual programs to perform
  specific task not to waste time in writing code
  for management task i.e.
• Resource Allocation
• Memory management
• Manage I/O

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Career Avenues

• Software Developer, System Architect, Program
  Manager
• RedHat, IBM, Microsoft, Google, Apple, Ubuntu,
  Solaris
• Courses available on Unix, Linux, are major
  widely recognized by IT industry..

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Career Avenues.

• Emerging trend of free OS like Linux, Google
  Chrome has increased professionals demand
• Mobile devices i.e Cell phones, Tablets
  Phablets have revolutionized demand of OS,
  Product i.e. Googles Android , Apples iOS,
  Blackberrys RIM are offering huge opportunity
  for developers.

• Disadvantages
• ERROR, can not afford !!!

• Advantages
• Good salary
• Innovation _at_ work

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Pre-requisite

• Basic Knowledge of computer Terminology.
• Basic Knowledge of Hardware devices.

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Objectives
Important Objectives of a Operating System are
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Learning Outcomes

• Define Operating System
• Functions of Operating System.
• Evolution of Operating System.
• System Components.
• Understanding of OS Structure.
• Operating System Services.
• System Calls.
• System Programs.
• Virtual Machine

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Computer System
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Operating System
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Definition of Operating System
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OS explained
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Facts
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How an OS Takes Control
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Function Of Operating System
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.What did the first operating system look like?
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1956-1965
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1965-1980
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(No Transcript)
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1980-Now
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Components of an operating system
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OS Structure - Simple Approach
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UNIX System Structure
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Layered OS Structure
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Layered Operating System
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Operating System Services
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• What is a system call?
• It provide the interface between a running
  program and the operating system
• Example- writing a simple program to read data
  from one file and copy that to another file

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Figure 1.1 Transition from User to Kernel Mode
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Processor Modes

• Modern processors typically can operate in 2
  modes "user mode" and "kernel mode " .
• User mode
• processor executes normal instructions in the
  user's program.
• Kernel mode
• processor executes both normal and privileged
  instructions
• Processor can access additional registers and
  memory address space that are accessible only in
  kernel mode

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• Types of system calls
• Process control
• File operations
• Device manipulation
• Information maintenance
• Communications

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Process control-

• End, abort
• Load, execute
• Create process, terminate process
• Get process attributes, set process attributes
• Wait for time
• Wait event, signal event
• Allocate and free memory

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File Management-

• Create file , delete file
• Open , close
• Read , write , reposition
• Get file attributes , set file attributes

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Device management-

• Request device , release device
• Read , write , reposition
• Get file attributes , set file attributes
• Logically attach or detach device

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Information maintenance-

• Get time or date , set time or date
• Get system data , set system data
• Get process, file, or device attributes
• Set process , file or device atributes

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Communication-

• Create , delete communication connections
• Send , receive message
• Transfer status information
• Attach or detach remote devices

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System calls

• System calls to the operating system are
  further classified according to the types of
  call-
• Normal Termination
• Abnormal termination
• Status Request
• Resource Request
• Input\ Output Request

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System Programs

• System programs provide a convenient environment
  for program development and execution
• Some of them are simply user interfaces to
  system calls. The can be divided into
• File manipulation
• Status information
• File modification
• Programming language support
• Program loading and execution
• Communication
• Application programs

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System Programs

• File management
• Create, delete, copy, rename, print, dump,
  list, and generally manipulate files and
  directories
• Status information-
• Some ask the system for info - date, time, amount
  of available memory, disk space, number of users
• Others provide detailed performance, logging, and
  debugging information

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System Program

• File modification-
• Several text editors may be available to create
  and modify the content of files stored on disk or
  other storage devices
• Programming language support-
• Compilers , assemblers , debuggers and
  interpreters for common languages(C, C..) are
  often provided to the user with the OS.

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System Program

• Program loading and execution-
• Once a program is assembled or complied , it must
  be loaded into memory to be executed
• Communication-
• These program provide the mechanism for creating
  virtual connections among processes, users , and
  computer system(allow user to send message,
  transfer file from one machine to another)
• Application program-

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Virtual Machines

• A virtual machine takes the layered approach to
  its logical conclusion.
• The fundamental idea behind a virtual machine is
  to abstract the hardware of single computer into
  several different execution environments ,
  thereby creating the illusion that each separate
  execution environment is running its own private
  computer.
• By using CPU scheduling and virtual memory
  techniques, an operating system can create the
  illusion that a process has its own processor
  with its own (virtual ) memory

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Virtual Machines (Cont.)

• (a) Non virtual machine (b) virtual machine

Non-virtual Machine
Virtual Machine
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Advantages/Disadvantages of Virtual Machines

• The virtual-machine concept provides complete
  protection of system resources since each virtual
  machine is isolated from all other virtual
  machines. This isolation, however, permits no
  direct sharing of resources.
• A virtual-machine system is a perfect vehicle for
  operating-systems research and development.
  System development is done on the virtual
  machine, instead of on a physical machine and so
  does not disrupt normal system operation.
• The virtual machine concept is difficult to
  implement due to the effort required to provide
  an exact duplicate to the underlying machine

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Thank you