Sistem Pengoperasian

Apakah Sistem Pengoperasian?
OS –
adalah satu set program untuk komputer mengendalikan sumbernya (resources) sendiri seperti unit pemprosesan pusat (central processing unit), ingatan utama (main memory), ingatan sekunder (secondary memory), peranti Input dan Output (Input/Output devices).
Oleh yang demikian perisian aplikasi pengguna (users application software) tidak perlu menyediakan semua arahan yang diperlukan oleh komputer.
Ini membolehkan pengaturcara memfokuskan usahanya kepada penyelesaian masalah kepada pelanggan.

A program that runs on the “raw” hardware and supports
-Resource Abstraction
-Resource Sharing
Abstracts and standardizes the interface to the user across different types of hardware
Virtual machine hides the messy details which must be performed
Manages the hardware resources
-Each program gets time with the resource
-Each program gets space on the resource
May have potentially conflicting goals:
Use hardware efficiently
Give maximum performance to each user

It is an extended machine
-Hides the messy details which must be performed
-Presents user with a virtual machine, easier to use

It is a resource manager
-Each program gets time with the resource
-Each program gets space on the resource

Operating system timeline

First generation: 1945 – 1955
Vacuum tubes
Plug boards

Second generation: 1955 – 1965
Transistors
Batch systems

Third generation: 1965 – 1980
Integrated circuits
Multiprogramming

Fourth generation: 1980 – present
Large scale integration
Personal computers

Next generation: ???
Systems connected by high-speed networks?
Wide area resource management?

First generation: direct input

Run one job at a time
Enter it into the computer (might require rewiring!)
Run it
Record the results
Problem: lots of wasted computer time!
Computer was idle during first and last steps
Computers were very expensive!
Goal: make better use of an expensive commodity: computer time.

Second generation: batch systems
-Bring cards to 1401
-Read cards onto input tape
-Put input tape on 7094
-Perform the computation, writing results to output tape
-Put output tape on 1401, which prints output

Third generation: multiprogramming

-Multiple jobs in memory
Protected from one another
-Operating system protected from each job as well
-Resources (time, hardware) split between jobs
-Still not interactive
*User submits job
*Computer runs it
*User gets results minutes (hours, days) later


Timesharing

Multiprogramming allowed several jobs to be active at one time
-Initially used for batch systems
-Cheaper hardware terminals -> interactive use
Computer use got much cheaper and easier
No more “priesthood”
-Quick turnaround meant quick fixes for problems

Jenis-jenis Sistem Pengoperasian

Mainframe operating systems: MVS
Server operating systems: FreeBSD, Solaris
Multiprocessor operating systems: Cellular IRIX
Personal computer operating systems: Windows, Unix
Real-time operating systems: VxWorks
Embedded operating systems
Smart card operating systems
Some operating systems can fit into more than one category
Sistem Pengoperasian Masa Nyata (Real Time Operating System)

corak perkhidmatan adalah sama seperti sistem pengoperasian kongsi masa.
Terdapat terminal yang terletak jauh dari permproses yang akan menghubungkan pengguna dengan sistem komputer.
Perbezaan :
Tidak akan proses kerja dengan serentak.
Tidak sesuai untuk pemprosesan kerja yang melibatkan banyak pengiraan.
Penggunaan biasanya untuk kerja-kerja bersangkutan input/output yang banyak seperti kerja-kerja input data dari terminal.
Exp : pendaftaran pelajar,pendaftaran modul, mesin ATM

Sistem Pengoperasian Masa Nyata (Real Time Operating System)
Biasanya digunakan untuk mengawal mesin di kilang, sistem industri ataupun peralatan saintifik yang memerlukan ketepatan.
Tidak digunakan untuk komputer di rumah

Berkelompok (Batch)
Perlaksanaan kerja adalah menurut penjadualan berjujukan
Setiap kerja akan dilaksanakan dengan segera apabila input diperoleh.
Jika terlalu banyak, kerja akan disimpan dahulu di dalam storan sekunder kemudian dilaksana satu persatu.
Kelemahan :
Keseluruhan fungsi/perkhidmatan komputer hanya tertumpu pada 1 kerja sahaja (tidak mempertimbangkan – kecil/besar, penting/tidak)
Kalau banyak kerja-kerja kecil, maka akan berlaku pembaziran penggunaan system komputer, terutama ‘masa pemproses’.

Kelebihan :
Ia menghindari status sumber menjadi tidak aktif walaupun tanpa interaksi dan penyeliaan manusia.
Ia digunakan pada kelas-kelas komputer
yang mahal untuk mengurangkan kos
dengan penggunaan sumber sumber
yang kerap.

Kongsi Masa (timesharing)
membenarkan sistem komputer digunakan secara serentak oleh ramai pengguna
Pengguna fikir, sistem komputer sedang berkhidmat khas padanya sahaja
Berlaku kerana sistem komputer memberi peruntukkan sehiris masa pemproses untuk setiap pengguna (peruntukkan masa pemproses sementara menunggu ‘save’ disket, input rangkaian, etc;)
Proses ini dinamakan ‘hirisan masa’
Apabila hirisan masa kerja A tamat – pergi ke hirisan masa kerja B
Exp: sistem carian buku di perpustakaan (OPAC –On-line Catalog), internet.

Teragih
tugas-tugas pengoperasian bagi bahagian berbeza program akan diagih-agihkan kepada beberapa pemproses (dua atau lebih komputer) tetapi berjalan secara serentak.
Setiap proses akan mempunyai ingatan sendiri dan saling berhubung melalui talian komunikasi.
Sejenis perkomputeran selari (parallel computing)
Exp : talian kelajuan tinggi(LAN)/talian telefon
Setiap pemproses adalah berbeza daripada saiz dan fungsi.
Kelebihan :
Perkongsian sumber yang cekap
Mempercepatkan komputasi
Meningkatkan kebolehharapan serta komunikasi

Multipengaturcaraan
digunakan secara meluas
membolehkan sistem komputer melarikan banyak kerja dengan serentak pada satu masa.
Setiap kerja akan dibahagikan kepada bahagian bahagian tertentu dan dilaksanakan satu persatu.
Perlaksanaan kerja menggunakan teknik hamparan a/cara
Modul-modul a/cara akan disimpan dalam storan sekunder, apabila diperlukan baru dimasukkan ke dalam ingatan utama.
Exp : save,print,taip,bold,etc
** Hamparan a/cara – biasanya digunakan apabila arahan-arahan/data-data yang diberikan melebihi jumlah ingatan fizikal)

OS FUNCTIONS
4 fungsi OS yg utama:-
1)Process Management (Pengurus Proses)
2)Main Memory Management (Pengurus Ingatan)
3)File Management (Pengurus Fail)
4)I/O System Management (Pengurus I/O)

Proses:
Aturcara yang dilaksanakan
Sebagai entiti yang memasuki pemproses (processor)
Berada dalam 3 keadaan
Berjalan pada CPU
Bersedia untuk berjalan pada CPU
Menunggu, biasanya pada peranti I/O
Apabila pemprosesan tamat
Proses dikeluarkan dari sistem

Satu proses boleh mencipta proses yang lain
Proses induk
Proses anak
Contoh :
proses menghitung matriks boleh mencipta beberapa proses menghitung lajur

Beberapa proses yang berlaku serentak mesti berkomunikasi antara satu sama lain
Untuk siapkan tugas bersama
Untuk bertanding menggunakan I/O
atau ingatan

A process tree
A created two child processes, B and C
B created three child processes, D, E, and F

1)Process Management
A process is a program in execution.
A process needs certain resources, including CPU time, memory, files, and I/O devices, to accomplish its task.
The operating system is responsible for the following activities in connection with process management.
Process creation and deletion.
process suspension and resumption.
Provision of mechanisms for:
process synchronization
process communication

2)Pengurus Fail
A file is a collection of related information defined by its creator.
Commonly, files represent programs (both source and object forms) and data.
The operating system is responsible for the following activities in connections with file management:
File creation and deletion.
Directory creation and deletion.
Support of primitives for manipulating files and directories.
Mapping files onto secondary storage.
File backup on stable (nonvolatile) storage media.

-Direktori simpan maklumat fail
Nama fail
Lokasi fizikal fail dlm cakera
Jenis fail
Maklumat pengurusan fail
Maklumat pemeliharaan fail

-Peruntukan storan fail
Fail dibahagikan kpd blok-blok fail sama saiz
Kedudukan blok tak semestinya bersebelahan.

Bagi menentukan blok-blok untuk 1 fail yg sama
Blok berpaut
Tiap-tiap blok dihubungkan antara satu dgn lain menggunakan penunjuk

Pemetaan fail
1 peta fail merekodkan kesemua blok–blok dlm 1 cakera
Bil blok
Nilai blok berikutnya.

Indeks blok
Guna direktori + indeks blok + maklumat fail

(3) Memory Management (Pengurus Ingatan)
Tugas utama
Menentukan bhg ingatan yg boleh diguna / tidak
Memelihara bhg ingatan yg telah digunakan oleh satu proses supaya tidak diganggu oleh proses lain
Menyediakan ruang ingatan yg secukupnya kpd proses
Kendalikan ingatan sebenar / maya.

Pengendalian Ingatan sebenar
Yg mudah – 1 proses berada dalam ingatan pada satu masa
Untuk ingatan besar – boleh kongsi dgn bbr proses
Masalah serpihan

Pengendalian Ingatan Maya
Untuk menyediakan 1 ruang ingatan yg lebih kepada proses

(4) I/O System Management
Also known as device management
The I/O system consists of:
A buffer-caching system
A general device-driver interface
Drivers for specific hardware devices

Tujuan
Sediakan peranti maya / pengendali peranti
Perantara dgn peranti sebenar
Gunakan cara pengkodan aksara yg tidak terikat dgn peranti sebenar
Membebaskan aturcara dri terikat dgn peranti tertentu seperti jenis pencetak
Lakukan operasi I/O dgn cekap dan kendalikan ralat
Memberi layanan sama kpd semua peranti

Program execution – system capability to load a program into memory and to run it.
I/O operations – since user programs cannot execute I/O operations directly, the operating system must provide some means to perform I/O.
File-system manipulation – program capability to read, write, create, and delete files.
Communications – exchange of information between processes executing either on the same computer or on different systems tied together by a network. Implemented via shared memory or message passing.
Error detection – ensure correct computing by detecting errors in the CPU and memory hardware, in I/O devices, or in user programs.

Additional functions exist not for helping the user, but rather for ensuring efficient system operations.
Resource allocation – allocating resources to multiple users or multiple jobs running at the same time.
Accounting – keep track of and record which users use how much and what kinds of computer resources for account billing or for accumulating usage statistics.
Protection – ensuring that all access to system resources is controlled.

DOS

DOS (Disk Operating System) was the first widely-installed operating system for personal computers.
It is a master control program that is automatically run when you start your PC.
DOS stays in the computer all the time letting you run a program and manage files.
It is a single-user operating system from Microsoft for the PC.
It was the first OS for the PC and is the underlying control program for Windows 3.1, 95, 98 and ME.
Windows NT, 2000 and XP emulate DOS in order to support existing DOS applications.
To use DOS, you must know where your programs and data are stored and how to talk to DOS.

UNIX

used in widely-sold workstation products from Sun Microsystems, Silicon Graphics, IBM, and etc
The UNIX environment and the client/server program model were important elements in the development of the Internet and the reshaping of computing as centered in networks rather than in individual computers.
Linux,
a UNIX derivative available in both "free software" and commercial versions, is increasing in popularity as an alternative to proprietary operating systems.
UNIX is written in C.
Both UNIX and C were developed by AT&T and freely distributed to government and academic institutions, causing it to be ported to a wider variety of machine families than any other operating system.
UNIX became synonymous with "open systems."

WINDOWS
Windows is a personal computer operating system from Microsoft
Windows contains built-in networking, which allows users to share files and applications with each other if their PCs are connected to a network.
In large enterprises, Windows clients are often connected to a network of UNIX and NetWare servers.
The server versions of Windows NT and 2000 are gaining market share, providing a Windows-only solution for both the client and server.
Windows is supported by Microsoft, the largest software company in the world, as well as the Windows industry at large, which includes tens of thousands of software developers.
However, Windows 95, 98, ME, NT, 2000 and XP are complicated operating environments.
Certain combinations of hardware and software running together can cause problems, and troubleshooting can be daunting.
Each new version of Windows has interface changes that constantly confuse users and keep support people busy,

MACINTOSH
The Macintosh (often called "the Mac")
introduced in 1984 by Apple Computer, was the first widely-sold personal computer with a graphical user interface (GUI).
designed to provide users with a natural, intuitively understandable, "user-friendly" computer interface.
This includes the mouse, the use of icons or small visual images to represent objects or actions, the point-and-click and click-and-drag actions, and a number of window operation ideas.
Microsoft was successful in adapting user interface concepts first made popular by the Mac in its first Windows operating system.
The primary disadvantage of the Mac is that there are fewer Mac applications on the market than for Windows.

MACINTOSH
The Macintosh has its own operating system, Mac OS which, in its latest version is called Mac OS X.
Mac versions today are powered by the PowerPC microprocessor, which was developed jointly by Apple, Motorola, and IBM.
While Mac users represent only about 5% of the total numbers of personal computer users
Macs are highly popular and almost a cultural necessity among graphic designers and online visual artists and the companies they work for.

Debian
Debian is a free operating system (OS) for your computer.
Debian uses the Linux kernel (the core of an operating system),
but most of the basic OS tools come from the GNU project; hence the name GNU/Linux.
Debian GNU/Linux provides more than a pure OS:
it comes with over 18733 packages, precompiled software bundled up in a nice format for easy installation on your machine.

ISSUES IN OS

2008 Technology of the Year Awards: Platforms

Mac OS X v10.5 Leopard

Apple's latest operating system release marks a turning point for the Mac.
Leopard users and developers immediately reap the benefits of Leopard's greatly enhanced Mac frameworks.
Almost nothing is buried for Apple or developers to uncover, while users gain from Apple's unsurpassed attention to usability and effortless integration from stem to stern.
Leopard will change the way you work with computers, entirely for the better

(Rujukan slide presentation KUIN & INTERNET)