os test 2

os test 2

1. os service

   • command-line
     • sometimes in kernel, sometimes by systems programs
     • shells - flavours depending on preference
       • linux - C shell, Bourne-Again shell, Korn shell
       • Many of the commands given at this level manipulate files: create, delete, list, print, copy, execute
     • some commands are built in
       • command line can set up the parameters to make the system call
     • names of programs
       • doesn't require shell modification
     • UNIX
       • does not understand the command, but simply loads a file from memory to execute the command
         • programmers can add new commands to the system easily by creating new files with the prope
   • graphics user interface (gui)
     • mouse, keyboard, monitor
     • invented @ xerox parc
   • batch
   • MS - gui with cli command shell; apple mac "aqua" gui interface with unix kernel underneath and shells available; unix and linux have cli with optional gui interfaces (cde, kde, gnome)
   • system calls - program - OS access
     • programming interfaces to os services
       • ways to pass parameters to the os - exact type and amt of information according to os and call
         • pass in registers - simplest
         • pushed onto stack then popped off - number and length not limited
         • stored in block, or table in memory - linux and solaris - number of parameters not limited
     • written in high level language such as c++ or c
     • accessed by programs via a high level API (application programming interface) rather than direct system call use
       • most common: win32 for windows, posix for posix based system such as unix, linux and mac os, and java api for jvm
     • number is indexed with each system call
       • system call interface invokes this sys call via the number, and returns any values
         • caller doesnt need to know how sys call is implemented, because api will give you instructions to be obeyed, and the caller needs to understand what the os will do as a result
     • types of system calls
       • process control
       • file management
       • device management
       • information maintenance
       • communications
         • message-passing model
         • shared memory model
       • protection

2. program execution

3. i/o operations

4. file system manipulation

5. communications

   • shared memory
   • message passing

6. error detection

   • debugging

7. resource allocation

8. accounting

9. protection and security

10. types of programs -

    • policy - what will be done mechanism - how to do it

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