Dalam Ilmu komputer, Sistem operasi atau dalam bahasa Inggris: operating system atau OS adalah perangkat lunak sistem yang bertugas untuk melakukan kontrol dan manajemen perangkat keras serta operasi-operasi dasar sistem, termasuk menjalankan software aplikasi seperti program-program pengolah kata dan browser web.

Secara umum, Sistem Operasi adalah software pada lapisan pertama yang ditaruh pada memori komputer pada saat komputer dinyalakan. Sedangkan software-software lainnya dijalankan setelah Sistem Operasi berjalan, dan Sistem Operasi akan melakukan layanan inti umum untuk software-software itu. Layanan inti umum tersebut seperti akses ke disk, manajemen memori, skeduling task, dan antar-muka user. Sehingga masing-masing software tidak perlu lagi melakukan tugas-tugas inti umum tersebut, karena dapat dilayani dan dilakukan oleh Sistem Operasi. Bagian kode yang melakukan tugas-tugas inti dan umum tersebut dinamakan dengan "kernel"

pendahuluan

Biasanya, istilah Sistem Operasi sering ditujukan kepada semua software yang masuk dalam satu paket dengan sistem komputer sebelum aplikasi-aplikasi software terinstall. Dalam Ilmu komputer, Sistem operasi atau dalam bahasa Inggris: operating system atau OS adalah perangkat lunak sistem yang bertugas untuk melakukan kontrol dan manajemen perangkat keras serta operasi-operasi dasar sistem, termasuk menjalankan software aplikasi seperti program-program pengolah kata dan browser web.

Secara umum, Sistem Operasi adalah software pada lapisan pertama yang ditempatkan pada memori komputer pada saat komputer dinyalakan. Sedangkan software-software lainnya dijalankan setelah Sistem Operasi berjalan, dan Sistem Operasi akan melakukan layanan inti umum untuk software-software itu. Layanan inti umum tersebut seperti akses ke disk, manajemen memori, skeduling task, dan antar-muka user. Sehingga masing-masing software tidak perlu lagi melakukan tugas-tugas inti umum tersebut, karena dapat dilayani dan dilakukan oleh Sistem Operasi. Bagian kode yang melakukan tugas-tugas inti dan umum tersebut dinamakan dengan "kernel" suatu Sistem Operasi

Kalau sistem komputer terbagi dalam lapisan-lapisan, maka Sistem Operasi adalah penghubung antara lapisan hardware dan lapisan software. Lebih jauh daripada itu, Sistem Operasi melakukan semua tugas-tugas penting dalam komputer, dan menjamin aplikasi-aplikasi yang berbeda dapat berjalan secara bersamaan dengan lancar. Sistem Operasi menjamin aplikasi software lainnya dapat menggunakan memori, melakukan input dan output terhadap peralatan lain, dan memiliki akses kepada sistem file. Apabila beberapa aplikasi berjalan secara bersamaan, maka Sistem Operasi mengatur skedule yang tepat, sehingga sedapat mungkin semua proses yang berjalan mendapatkan waktu yang cukup untuk menggunakan prosesor (CPU) serta tidak saling mengganggu.

Dalam banyak kasus, Sistem Operasi menyediakan suatu pustaka dari fungsi-fungsi standar, dimana aplikasi lain dapat memanggil fungsi-fungsi itu, sehingga dalam setiap pembuatan program baru, tidak perlu membuat fungsi-fungsi tersebut dari awal.

Sistem Operasi secara umum terdiri dari beberapa bagian:

1. Mekanisme Boot, yaitu meletakkan kernel ke dalam memory
2. Kernel, yaitu inti dari sebuah Sistem Operasi
3. Command Interpreter atau shell, yang bertugas membaca input dari pengguna
4. Pustaka-pustaka, yaitu yang menyediakan kumpulan fungsi dasar dan standar yang dapat dipanggil oleh aplikasi lain
5. Driver untuk berinteraksi dengan hardware eksternal, sekaligus untuk mengontrol mereka.

Sebagian Sistem Operasi hanya mengizinkan satu aplikasi saja yang berjalan pada satu waktu (misalnya DOS), tetapi sebagian besar Sistem Operasi baru mengizinkan beberapa aplikasi berjalan secara simultan pada waktu yang bersamaan. Sistem Operasi seperti ini disebut sebagai Multi-tasking Operating System (misalnya keluarga sistem operasi UNIX). Beberapa Sistem Operasi berukuran sangat besar dan kompleks, serta inputnya tergantung kepada input pengguna, sedangkan Sistem Operasi lainnya sangat kecil dan dibuat dengan asumsi bekerja tanpa intervensi manusia sama sekali. Tipe yang pertama sering disebut sebagai Desktop OS, sedangkan tipe kedua adalah Real-Time OS

Sistem Operasi saat ini

Sistem operasi-sistem operasi utama yang digunakan komputer sistem umum (termasuk PC, komputer personal) terbagi menjadi 3 kelompok besar:

1. Keluarga Microsoft Windows - yang antara lain terdiri dari Windows Desktop Environment (versi 1.x hingga versi 3.x), Windows 9x (Windows 95, 98, dan Windows ME), dan Windows NT (Windows NT 3.x, Windows NT 4.0, Windows 2000, Windows XP, Windows Server 2003, Windows Vista, Windows 7 (Seven) yang akan dirilis pada tahun 2009, dan Windows Orient yang akan dirilis pada tahun 2014)).
2. Keluarga Unix yang menggunakan antarmuka sistem operasi POSIX, seperti SCO UNIX, keluarga BSD (Berkeley Software Distribution), GNU/Linux, MacOS/X (berbasis kernel BSD yang dimodifikasi, dan dikenal dengan nama Darwin) dan GNU/Hurd.
3. Mac OS, adalah sistem operasi untuk komputer keluaran Apple yang biasa disebut Mac atau Macintosh. Sistem operasi yang terbaru adalah Mac OS X versi 10.4 (Tiger). Awal tahun 2007 direncanakan peluncuran versi 10.5 (Leopard).

Sedangkan komputer Mainframe, dan Super komputer menggunakan banyak sekali sistem operasi yang berbeda-beda, umumnya merupakan turunan dari sistem operasi UNIX yang dikembangkan oleh vendor seperti IBM AIX, HP/UX, dll.

Information technology

Information technology (IT), as defined by the Information Technology Association of America (ITAA), is "the study, design, development, implementation, support or management of computer-based information systems, particularly software applications and computer hardware."[1] IT deals with the use of electronic computers and computer software to convert, store, protect, process, transmit, and securely retrieve information.

Today, the term information has ballooned to encompass many aspects of computing and technology, and the term has become very recognizable. IT professionals perform a variety of duties that range from installing applications to designing complex computer networks and information databases. A few of the duties that IT professionals perform may include data management, networking, engineering computer hardware, database and software design, as well as the management and administration of entire systems.

When computer and communications technologies are combined, the result is information technology, or "infotech". Information technology is a general term that describes any technology that helps to produce, manipulate, store, communicate, and/or disseminate information. Presumably, when speaking of Information Technology (IT) as a whole, it is noted that the use of computers and information are associated.


Information and communication technologies
Information and communication technologies (ICT) is an umbrella term that covers all technical means for processing and communicating information. While this technically encompasses pre-digital technologies, including paper-based writing, it is most often used to describe digital technologies including methods for communication (communication protocols, transmission techniques, communications equipment, media (communication)), as well as techniques for storing and processing information (computing, data storage, etc.) The term has gained popularity partially due to the convergence of information technology (IT) and telecom technology.

ICT allows users to participate in a rapidly changing world in which work and other activities are increasingly transformed by access to varied and developing technologies. By this definition, you could almost say ICT is technology's version of economic growth, to satisfy the needs and wants of the community over time.

ICT tools can be used to find, explore, analyze, exchange and present information responsibly and without discrimination. ICT can be employed to give users quick access to ideas and experiences from a wide range of people, communities and cultures.

THE COMPONENTS OF A COMPUTERS

THE SYSTEM UNIT
Whether you are a home user or a business user, you most likely will make the decision to purchase a new computer or upgrade an existing computer within the next several years. Thus, you should understand the purpose of each component in a computer.
The motherboard
The motherboard, sometimes called a system board, is the main circuit board of the system unit. Many electronic components attach to the motherboard. Others are built into it. Memory chips are installed on memory cards (modules) that fit in a slot on the motherboard.
A computer chip is a small piece of semiconducting material, usually silicon, on which integrated circuit contains many microscopic pathways capable of carrying electrical current. Each integrated circuit can contain millions of elements such as resistor, capacitors, and transistors. A transistor, for example, with can act as an electronic switch that opens or closes the circuit for electrical charges. Most chips are no bigger than one half inch square. Manufactures package chips so that the chips can be attached to a circuit board, such as a motherboard or an adapter card. Specific types of chips are discussed later in the chapter.
PROCESSOR
The processor, also called the central processing unit (CPU), interprets and carries out the basic manages most of a computer’s operations. On larger computers, such a mainframes and supercomputers, the various functions performed by the processor extend over many separate chips and often multiple circuit board. On a usually are on a single chip. Some computer and chip manufactures use the term microprocessor to refer to a personal computer processor chip.
Most processor chip manufacturers now offer multi core processor. A multi core processor is a single chip two or more separate processors. Two common multi core processor used today are dual core and quad core. A dual-core processor is a chip that contains two separate processors. Similarly, a quad-core processor is a chip whit four separate processors. Ach processor on a multi-core chip generally runs at a slower clock speed than a singe-core processor, but multi-core chips typically increase overall performance. For example, although a dual-core processor does not double the processing unit speed of a single-core. Processor, it can approach those speeds. The performance increase is especially noticeable when users are running multiple programs simultaneously such as less antivirus software, spyware remover, e-mail program, instant messaging, media player, CD burning software, and photo editing software. Multi-core processors also are energy efficient, requiring lower levels of power consumptions and emitting less heat in the system unit.

THE COMPONENTS OF A COMPUTERS

A computer contains many electric, electronic, and mechanical components know as hardware. These components include input devices, output devices, a system unit, storage devices, and communications devices.
INPUT DEVICES
An input device is any hardware component that allows you enter data and instructions into a computer. Six widely used input devices are the keyboard, mouse, microphone, scanner, digital camera, and web cam.
A computer keyboard contains keys you press to enter data into the computers. For security purposes, some keyboards have a built in fingerprint reader, which allows you to work with the computer only if your fingerprint is recognized.
A mouse is small handheld device. With the mouse, you control movement of small symbol on the screen, called the pointer, and you make selections from the screen.
A microphone allows you to speak into the computer. A scanner convert printed material (such as text and pictures) into a form the computer can use.
With a digital camera, you take pictures and then transfer them to the computer or printer instead of storing the images on traditional film. A web cam is digital video camera that allows you to create movies or take still pictures electronically.
OUTPUT DEVICES
An output device is any hardware component that conveys information to one o more people. Four commonly used output devices are a printer, a monitor, speakers, and a portable media player.
A printer produces text and graphics on a physical medium such as paper. A monitor displays text, graphics, and videos on a screen. Speakers allow you to hear music, voice, and other audio (sound). You can transfer audio, video, and digital images from a computer to a potable media player and then listen to the audio, watch the video, or view the images on the media player.
SYSTEM UNIT
The system unit is a case that contains the electronic components of the computer that are used to process data. The circuitry of the system unit usually is part of or is connected to a circuit board called the motherboard.
Two main components on the motherboard are the processor and memory. The processor is the electronic component that interprets and carries out the basic instructions that operate the computer. Memory consists of electronic components that store instructions waiting to be executed and data needed by those instructions. Although some forms of memory are permanent, most memory keeps data and instruction temporarily, which means its contents are erased when the computer is shut off.
STORAGE DEVICES
Storage holds data, instructions and information for future use. For example, computers can store hundreds or millions of customer names and addresses. Storage holds these items permanently.
A computer keeps data, instructions, and information on storage media. Examples of storage media are USB flash drives, hard disks, CDs, DVDs, and memory cards. A storage device records (writes) and or retrieves (reads) items to and from storage media. Drives and readers/writers, which are types of storage devices, accept a specific kind of storage media. For example, a DVD drive (storage device) accepts a DVD (storage media). Storage devices often function as a source of input because they transfer items from storage to memory.
A USB flash drive is a portable storage device that is small and lightweight enough to be transported on a keychain or in pocket. The average USB flash drive can hold about 2 billion characters. You plug a USB flash drive in a special, easily accessible opening on the computer.
A hard disk provides much greater storage capacity than a USB flash drive. The average hard disk can hold more than 320 billion characters. Hard disks are enclosed in an airtight, sealed case. Although some are portable, most are housed inside the system unit. Portable hard disks are either external or removable. An external hard disk is a separate, free standing unit, whereas you insert and remove a removable hard disk from the computer or a device connected to the computer.
A compact disc is flat, round, portable metal disc with a plastic coating. One type of compact disc is a CD, which can hold from 650 million to 1 billion characters. You can access a CD using most CD and DVD drives. Another type of compact disc is a DVD, some of which have enough storage capacity to store two full length movies or 17 billion characters. To access a DVD, you need a DVD drive.
Some portable devices, such as digital cameras, use memory cards as the storage media. You then can transfer the stored items, such as digital photos, from the memory card to a computer or printer using a card reader/writer.
COMMUNICATIONS DEVICES
A communications devices is a hardware component that enables a computer to send (transmit) and receive data, instructions, and information to and from one or more computers. A widely used communications device is a modem.
Communications occur over cables, telephones lines, cellular radio networks, satellites, and other transmission media. Some transmission media, such as satellites and cellular radio networks, are wireless, which means they have no physical lines or wires.