The document discusses various operating system structures including batch, time-sharing, distributed, and network operating systems. It describes the layers of common operating system architectures like UNIX with the kernel providing core functions and systems programs interfacing with hardware. Finally, it analyzes hybrid operating system designs used by Linux, Solaris, Windows, iOS, and Android that combine aspects of monolithic and microkernel-based systems.

1. Name: Nasrin akter borsha
ID:182-15-2133
Section: PC(A) Course code: CSE323
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Operating-System
Structures
ASSIGNMENT

2. An operating system is system softwarethat manages computer hardware,
softwareresources, and provides common services for computer programs.
Various Types of OS:
 Batch OS, Time Sharing OS, Distributed OS, Network OS (LAN),
Real time OS.
Operating-System Structures
Operating System Services: Almostall operating systemshaveanuser interface.
Has I/O operation. Programs needs file to read/write to run, delete data. It can
execute program . It can detect errors . It has strong security system and many
resource allocations here.
System Calls: System-callinterface maintains a table indexed according to given
numbers.Herethe userswillnotknowabout it butneed to obey API as byAPI Most
details of OS interface hidden.
UNIX: The UNIX OS consists of two separable parts;
1. Systems programs: Itworksbelow thesystem-callinterface and
above the physicalhardware to consists of everything.
2. The kernel: Provides the file system, CPUscheduling, memory
management, and other operating-systemfunctions; a large number
of functions for one level.
Layered Approach: Operating systemhas two layers. The bottom layer called
layer0 that is the hardware; the highest called layer N is the user interface.
Microkernel System Structure: MicrokernelSystemStructure Communication
takes place between user modules using messagepassing. Ithas somebenefits
because it is easier to extend a microkernel and to portthe operating systemto
new architectures. Itis morereliable and more secure.
Modules: Mostmodern operating systems implement loadable kernel modules.
Ituses object-oriented approach and core component is separate. Each is
loadable as needed within the kernel and more flexible and Linux, Solaris, etc.

3. Applications
Application Framework
Android runtime
Core Libraries
Dalvik
virtual machine
Libraries
Linux kernel
SQLite openGL
surface
manager
webkit libc
media
framework
Hybrid Systems: Hybrid combines multiple approaches to address performance,
security, usability needs. Fromthem;
Linux and Solaris kernels in kernel address space, so monolithic, plus modular for
dynamic loading of functionality and Windows mostly monolithic, plus
microkernelfor different subsystempersonalities.
iOS: Apple mobile OS for iPhone, iPad it is Structured on Mac OS X, does not run
OS X applications natively. Cocoa Touch Objective-CAPI for developing apps.
Media services layer for graphics, audio, video
Android: It is an open source, Developed by Open Handset Alliance (mostly
Google) Itis kind of Similar stack to IOS. Runtimeenvironment includes core set of
libraries and Dalvik virtual machine.
The basement of its on Linux kernel but modified
1. Provides process, memory, device-driver management
2. Adds power management
Diagram: Android Architecture