Cse 331 Lecture Slides

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Lecture 1 Introduction
Lecture 2 Processes

OS Services cont…

    • Communication
      • Data transfer between processes may be required from time to time
      • The processes may be on one computer or different computer connected over a computer network
    • Error Detection
      • Errors may occur in the CPU, I/O devices or in memory devices
      • The OS constantly needs to be aware of possible errors
      • It should take the appropriate action to ensure correct and consistent computing
    • Accounting
      • To keep track of which users use how much and what kinds of computer resources

OS User Interface

  • Command Interpreter
    • CLI allows direct command entry
    • Fetches a command from a user and executes it
    • They are either implemented in kernel or by systems programs
    • Eg Linux shell, Windows shell
  • GUI
    • User friendly desktop metaphor interface
    • Files, programs, action etc are represented using icons
    • Mouse action over objects on the interface cause various actions (Provide information, option, execute function, open directory etc)
    • Many systems now include both CLI and GUI interfaces

System Calls

  • System calls provide the interface between a process and the
  • operating system.

  • These calls are generally available as assembly-language instructions.
  • Typically written in a high-level language (C or C++)
  • allow user-level processes to request some services from the operating system.
  • E.g. for I/O a process involves a system call telling the operating system to read or write particular area and this request is satisfied by the operating system.

System Calls cont..

  • The following different types of system calls provided by an OS:
  • Process control
    • End, abort
    • Load, execute
    • Create, terminate
    • Get attributes, set attributes
    • Allocate, free memory
  • File management
  • Device management
  • Communication
    • Create, delete communication connection
    • Send, receive message
    • Transfer status information
    • Attach or detach remote devices

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