إنجازات كبرى في تطوير نظم التشغيل Major Achievements

memory mangment cont.
ALL achieved by Virtual Memory concept
allows programs to address memory from a logical point of view
Without regard to the limits of RAM

Different Architectural Approaches
مقاربات معمارية مختلفة
include:
 Microkernel architecture
 Multithreading
 Symmetric multiprocessing (SMP)
 Distributed operating systems
 Object-oriented design
 
Microkernel architecture
only a few essential functions in kernel
-Virtual Memory
-Basic scheduling
-Interprocess communication (IPC)
Other OS services are provided by processes
 
Multithreading
Process is divided into threads that can run concurrently
Thread: Dispatchable unit of work
-- executes sequentially and is interruptible
ينفذ بالتسلسل وقابل للمقاطعة
 
) Symmetric
multiprocessing (SMP)
[ltr]•SMP system has[/ltr]
[ltr]–multiple CPUs[/ltr]
[ltr]–shared memory[/ltr]
[ltr]–shared I/O[/ltr]
[ltr]•All CPUs perform same functions[/ltr]
[ltr]•OS schedules processes/threads across all CPUs.[/ltr]
[ltr]•Examples?[/ltr]
[ltr]–Multi-core[/ltr]
[ltr]–GPUs[/ltr]

[ltr][size=43]•[/size][size=43]Advantages:[/size][/ltr]
[ltr][size=37]1.[/size][size=37]Performance[/size][/ltr]
[ltr][size=32]•[/size][size=32]Allowing parallel processing[/size][/ltr]
[ltr][size=37]2.[/size][size=37]Availability[/size][/ltr]
[ltr][size=32]•[/size][size=32]Failure of a single process does not halt the system[/size][/ltr]
[ltr][size=37]3.[/size][size=37]Incremental Growth[/size][/ltr]
[ltr][size=32]•[/size][size=32]Additional processors can be added.[/size][/ltr]
[ltr][size=37]4.[/size][size=37]Scaling[/size][/ltr]

 
[ltr]With multiprogramming, only one process can execute at a time; [/ltr]
[ltr]• meanwhile all other processes are waiting for the processor.[/ltr]

[ltr]With multiprocessing, more than one process can be running simultaneously, each on a different processor.[/ltr]