Chapter 2: OS Structures

Chapter 2: OS Structures

1. OS Services

   • systems provide an environment for the execution of programs.
   • functions helpful to the user:
     • User Interface
       • Command-Line
       • Graphics User Interface
       • Batch Interface
     • Program execution -
     • I/O operations
     • File-System manipulation
     • communications
       • – Processes may exchange information, on same computer or between computers over a network
     • Error Detection
       • Possible Errors
         • May occur in the CPU and memory hardware, in I/O devices, in user program
       • For each type of error, OS should take the appropriate action to ensure correct and consistent computing
   • functions for ensuring efficient operation of system itself via resource sharing
     • Resource allocation
       • When multiple users or multiple jobs are running concurrently, resources must be allocated to each of them
         • Ex. CPU cycles, main memory, file storage, I/O devices.
     • Protection and security
       • owners of information stored in a multiuser or networked computer system may want to control use of that information, concurrent processes should not interfere with each other
     • Accounting
       • To keep track of which users use how much and what kinds of computer resources

2. OS Interface

   • Command Line Interpreter (CLI)
     • The main function of the command interpreter is to get and execute the next user-specified command.
   • GUI
     • User-friendly desktop metaphor interface
       • Ex. mouse, keyboard, and monitor Icons represent files, programs, actions, etc