(C191) Operating Systems for programmers - Unit 2

User Interface

-These allow for the user to interact with the system services via system calls (typically written in C/C++).

-Can be GUI, Command Line, or Batch

System services that are helpful to the user

program execution, I/O operations, file-system

manipulation, communications, and error detection

Services that ensure efficient OS operation

resource allocation, accounting, protection and security

APIs (Application Program Interface) examples

Win32, POSIX, Java

system call relation with numbers

System call interface maintains a table indexed according to these numbers

How parameter are passed into the OS by system call

- Passing in registers, address of parameter stored in a block, pushed onto the stack by the program and popped off by the OS

-Block and stack methods do not limit the number

or length of parameters being passed

Process Control

-end, abort, load, execute, create/terminate process, wait, allocate/free memory

File management

- system calls include: create/delete file, open/close file, read, write, get/set attributes

Device Management

- system calls: request/release device, read, write, logically attach/detach devices

Information maintenance

- system calls: get/set time,

get/set system data, get/set process/file/device attributes

Communication

- system calls: create/delete communication connection, send/receive, transfer status information

OS layered approach

- The operating system is divided into a number of layers (levels), each built on top of lower layers. The bottom layer (layer 0), is the hardware; the highest (layer N) is the user interface

- With modularity, layers are selected such that each uses functions (operations) and services of only lower-level layers

Virtual Machine

- uses layered approach, treats hardware and the OS kernel as though they were all hardware.

-Host: creates the illusion that a process has its own processor and own virtual memo

- Each guest provided with a 'virtual' copy of the underlying computer

Host

creates the illusion that a process has its own processor and own virtual memo

Core Dump

generated file that contains the memory of the application failures process

Crash Dump

Dump File that contains system failure kernel memory