operating systems

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  • 1. Operating SystemsOperating SystemsAUGUSTNE C THEVERKUNNELS2 M.TECH (IE & M)ROLL NO: 021
  • 2. What is OS? Operating System is a software It is the software that enables all the programs we use. The OS organizes and controls the hardware. OS acts as an interface between the applicationprograms and the machine hardware. Examples: Windows, Linux, Unix, etc.,2
  • 3. FUNCTIONS OF OPERATING SYSTEM Convenience: An OS makes a computer moreconvenient to use. Efficiency: An OS allows the computer systemresources to be used in an efficient manner. Ability to Evolve: It helps in the properfunctioning of the computer without interruption3
  • 4. Structure of Operating System:Application ProgramsSystem ProgramsSoftware (Operating System)HARDWARE(Contd…)4
  • 5. Structure of Operating System(Contd…): The structure of OS consists of 4 layers:1. HardwareHardware consists of CPU, Main memory, I/ODevices, etc,2. Software (Operating System)Software includes process managementroutines, memory management routines, I/Ocontrol routines, file management routines.(Contd…)5
  • 6. Structure of Operating System(Contd…):3. System programsThis layer consists of compilers, Assemblers,linker etc.4. Application programsThis is dependent on users need. Ex. Railwayreservation system, Bank databasemanagement etc.,6
  • 7. Batch Processing: In Batch processing same type of jobs batch (BATCH- aset of jobs with similar needs) together and execute at atime. The OS was simple, its major task was to transfercontrol from one job to the next. The job was submitted to the computer operator in formof punch cards. At some later time the output appeared. The OS was always resident in memory. (Ref. Fig. nextslide) Common Input devices were card readers and tapedrives.7
  • 8. Batch Processing (Contd…): Common output devices were line printers, tape drives,and card punches.OSUserprogramarea8
  • 9. Multiprogramming: Multiprogramming is a technique to execute number ofprograms simultaneously by a single processor. In Multiprogramming, number of processes reside inmain memory at a time. The OS picks and begins to executes one of the jobs inthe main memory. If any I/O wait happened in a process, then CPUswitches from that job to another job.9
  • 10. Multiprogramming (Contd…):OSJob 1Job 2Job 3Job 4Job 5• Figure dipicts the layout ofmultiprogramming system.• The main memory consists of 5jobs at a time, the CPU executesone by one.Advantages:•Efficient memory utilization•CPU is never idle, soperformance increases.10
  • 11. Time Sharing Systems: Time sharing, or multitasking, is a logical extension ofmultiprogramming. Multiple jobs are executed by switching the CPUbetween them. In this, the CPU time is shared by different processes, soit is called as “Time sharing Systems”. Examples: Multics, Unix, etc.,11
  • 12. Types of OS:Operating System can also be classified as,- Single User Systems Multi User Systems12
  • 13. Single User Systems: Provides a platform for only one user at atime. They are popularly associated with Desk Topoperating system which run on standalonesystems where no user accounts arerequired. Example: DOS13
  • 14. Multi-User Systems: Provides regulated access for a number of users bymaintaining a database of known users. Refers to computer systems that support two or moresimultaneous users. Another term for multi-user is time sharing. Ex: All mainframes and are multi-user systems. Example: Unix14
  • 15. UNIX OPERATING SYSTEM Unix is a multitasking, multi-user computer operatingsystem It is written in C language UNIX can be used in a wide variety of computers15
  • 16. MICROKERNEL BASED OPERATINGSYSTEM A set of independent system servers using theprimitive, generic services of a microkernel. The micro-kernel provides a virtual machine forprocessor use, memory allocation andcommunication between operating systemcomponents16
  • 17. MICROKERNEL BASED OPERATING SYSTEM In order to make an OS portable it is necessaryto make the machine dependent part as small aspossible The microkernel was developed in the early1990s to overcome the problems concerningportability, extensibility, and reliability of kernels Microkernel is a very small core of an operatingsystem17
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