Operating System Structures (Services (User Interface (Different types of…
Operating System Structures
Different types of UI. Command line interface uses text commands. Batch interface executes files in which commands and directives are written. Graphical interface is a window based system.
The system must be able to load a program to memory and execute that program. The program needs to be able to terminate its execution normally or abnormally.
For efficiency and protections users cannot control I/O devices. OS must provide means to do I/O.
File System Manipulation
Some SO include permissions to allow or deny file access based on file ownership. Many SO provide different file systems. Some to allow personal choice and some to add specific features.
Can be implemented via shared memory in which two or more processes read and write to the shared section of memory. Or message passing in which information in predefined formats are moved between processes.
For each possible error the SO should take appropriate action to ensure correct and consistent computing.
Many SO do not have well defines structures. Such systems start small and limited and then grow beyond the original scope.
OS can be broken into smaller pieces and more appropriate. This SO can retain much greater control over the computer and applications.
An SO called Mach that modularized the kernel using the microkernel approach.
A program must be able to end its execution or abort it because an error occurred. A debugger is used to locate errors and bugs in the program.
This type of system calls manage what operations users can do with files. This means how the user opens, closes, modifies, moves, read, and writes files.
All processes that happen in the computer need some kind of resource from the computer. Processes are executed when the computer has enough resources available otherwise it is prone to a queue. This resources commonly come in devices such as disks or drivers.
Many of the system calls between the user and the SO are only use for the passing of information.
Message Passing Model
Communicating processes exchange messages with one another to transfer information. Messages between processes can be exchanged directly or indirectly through a mailbox.
Shared Memory Model
Processes use system calls to gain access to regions of memory owned by other processes. This requires that two or more processes agree to share their memory space. Processes are responsible for not writing to the same location simultaneously.
Provides tools to limit and control how users access different resources and files. This way only authorized users can do certain things.