6 multiprogramming & time sharing

6 multiprogramming & time sharing

• 1.
  Basics of OperatingSystems : Multiprogramming & Time Sharing 1
• 2.
  Recap In the lastclass, you have learnt about • Spooling • Buffering 2
• 3.
  Objectives On completion ofthis period, you would be able to know • Multiprogramming • Time Sharing 3
• 4.
  Multiprogramming • A programunder execution is called a process • Serial execution of the program causes either the process or I/O devices to be ideal at some time even if the input job stream is never empty – a problem ( refer next slide ) • Solution to this problem is to assign some other work to the processor and I/O devices when they are idle • Allow programs to execute concurrently by assigning pending work to under utilized components 4
• 5.
  Example Program 1 Program 2 P1 IDLE P1 IDLE P1 P2 IDLE P2 IDLE P2 Time Processor Activity Multi Programming 5
• 6.
  Multiprogramming • Previous Figureillustrates a possible scenario of concurrent execution of the two programs • It starts with the processor executing the first computational sequence program 1 • Instead of idling during the I/O sequence of program 1, the processor is assigned to the first computation sequence of the program 2, which is assumed to be in memory and awaiting for execution • When this work is done, the processor is assigned to program 1 again, then to program 2, and so forth 6
• 7.
  Multiprogramming (Contd..) • Performanceof processor may be improved by interleaved execution of programs • With a single processor, parallel execution of program is not possible, and at most one program can be in control of the processor at any time 7
• 8.
  Multiprogramming (Contd..) • Itachieves 100% processor utilization with only two active programs • Multiprogramming has been employed to increase resource utilization of a computer system and to support multiple, simultaneously active users 8
• 9.
  Multiprogramming (Contd..) • Multiprogrammingsystem is provided by time sharing systems found in many university computer centers • Time sharing systems support multiple interactive users • System and user programs, as well as data, are kept on the secondary storage which is managed by the file system 9
• 10.
  Time sharing • Timesharing is the logical extension of Multiprogramming • Time sharing systems executes multiple jobs by switching among them ( refer next slide ) • Switches occurs frequently so that the user can interact with each program while it is running • Each program executes for a fixed time quantum 10
• 11.
  Example Program 1 Program 2 P1 P2 P1 P2 P1 P2 Time Time Sharing 11
• 12.
  Timesharing (Contd..) • Timesharing requires an interactive computer system • i.e. direct communication between the user and the system • Time sharing OS allows many users to share the computer simultaneously • Each action or command in a time shared system is short, only a little of CPU time is required for each user 12
• 13.
  Timesharing (Contd..) • Thesystem switches rapidly from one user to the next • User gets the impression that the entire system is dedicated to his use • Time shared operating system uses CPU scheduling and Multiprogramming to provide • each user with a small portion of a time-shared system 13
• 14.
  Frequently Asked Questions •Explain Multiprogramming systems • Explain Time Sharing systems 14
• 15.
  Quiz • Programs aredeveloped and executed in the interactive mode Yes No 15
• 16.
  Quiz • A programin execution is called process Yes No 16
• 17.
  Click here tosee Operating Systems Basics of Operating Systems Definition of Operating Systems 1.4 Know about concept of spooling and buffering ppt Other subject materials • Web designing • Micro processors • C++ tutorials • java home 17