function of OS

The main functions of an OS include:
In a multitasking operating system where multiple programs can be running at the same time, the operating system determines which applications should run in what order and how much time should be allowed for each application before giving another application a turn.
It manages the sharing of internal memory among multiple applications.
It handles and monitors input and output to and from attached hardware devices, such as hard disks, printers, and dial-up ports. [8]
It sends messages to each application or interactive user (or to a system operator) about the status of operation and any errors that may have occurred.
It can offload the management of what are called batch jobs (for example, printing) so that the initiating application is freed from this work.
On computers that can provide parallel processing, an operating system can manage how to divide the program so that it runs on more than one processor at a time.
Scheduling the activities of the CPU and resources to achieve efficiency and prevention of deadlock

Operating System

An operating system is the software on a computer that manages the way different programs use its hardware, and regulates the ways that a user controls the computer.[1][2] Operating systems are found on almost any device that contains a computer with multiple programs—from cellular phones and video game consoles to supercomputers and web servers. Some popular modern operating systems for personal computers include Microsoft Windows, Mac OS X, and Linux[3] (see also: list of operating systems, comparison of operating systems).
Because early computers were often built for only a single task, operating systems did not exist in their proper form until the 1960s.[4] As computers evolved into being devices that could run different programs in succession, programmers began putting libraries of common programs (in the form of computer code) onto the computer in order to avoid duplication and speed up the process. Eventually, computers began being built to automatically switch from one task to the next. The creation of runtime libraries to manage processing and printing speed came next, which evolved into programs that could interpret different types of programming languages into machine code. When personal computers by companies such as Apple Inc., Atari, IBM and Amiga became popular in the 1980s, vendors began adding features such as software scheduling and hardware maintenance.
An operating system can be divided into many different parts. One of the most important parts is the kernel, which controls low-level processes that the average user usually cannot see: it controls how memory is read and written, the order in which processes are executed, how information is received and sent by devices like the monitor, keyboard and mouse, and deciding how to interpret information received by networks. The user interface is the part of the operating system that interacts with the computer user directly, allowing them to control and use programs. The user interface may be graphical with icons and a desktop, or textual, with a command line. Another similar feature is an Application programming interface, which is a set of services and code libraries that let applications interact with one another, as well as the operating system itself. Depending on the operating system, many of these components may not be considered an actual part. For example, Windows considers its user interface to be part of the operating system, while many versions of Linux do not.

Secondry Storage

Secondary storage (or external memory) differs from primary storage in that it is not directly accessible by the CPU. The computer usually uses its input/output channels to access secondary storage and transfers the desired data using intermediate area in primary storage. Secondary storage does not lose the data when the device is powered down—it is non-volatile. Per unit, it is typically also two orders of magnitude less expensive than primary storage. Consequently, modern computer systems typically have two orders of magnitude more secondary storage than primary storage and data is kept for a longer time there.
In modern computers, hard disk drives are usually used as secondary storage. The time taken to access a given byte of information stored on a hard disk is typically a few thousandths of a second, or milliseconds. By contrast, the time taken to access a given byte of information stored in random access memory is measured in billionths of a second, or nanoseconds. This illustrates the very significant access-time difference which distinguishes solid-state memory from rotating magnetic storage devices: hard disks are typically about a million times slower than memory. Rotating optical storage devices, such as CD and DVD drives, have even longer access times. With disk drives, once the disk read/write head reaches the proper placement and the data of interest rotates under it, subsequent data on the track are very fast to access. As a result, in order to hide the initial seek time and rotational latency, data are transferred to and from disks in large contiguous blocks.
When data reside on disk, block access to hide latency offers a ray of hope in designing efficient external memory algorithms. Sequential or block access on disks is orders of magnitude faster than random access, and many sophisticated paradigms have been developed to design efficient algorithms based upon sequential and block access . Another way to reduce the I/O bottleneck is to use multiple disks in parallel in order to increase the bandwidth between primary and secondary memory.[2]
Some other examples of secondary storage technologies are: flash memory (e.g. USB flash drives or keys), floppy disks, magnetic tape, paper tape, punched cards, standalone RAM disks, and Iomega Zip drives.
The secondary storage is often formatted according to a file system format, which provides the abstraction necessary to organize data into files and directories, providing also additional information (called metadata) describing the owner of a certain file, the access time, the access permissions, and other information.
Most computer operating systems use the concept of virtual memory, allowing utilization of more primary storage capacity than is physically available in the system. As the primary memory fills up, the system moves the least-used chunks (pages) to secondary storage devices (to a swap file or page file), retrieving them later when they are needed. As more of these retrievals from slower secondary storage are necessary, the more the overall system performance is degraded.

Primary Storage

[edit] Primary storage
Direct links to this section: Primary storage, Main memory, Internal Memory.
Primary storage (or main memory or internal memory), often referred to simply as memory, is the only one directly accessible to the CPU. The CPU continuously reads instructions stored there and executes them as required. Any data actively operated on is also stored there in uniform manner.
Historically, early computers used delay lines, Williams tubes, or rotating magnetic drums as primary storage. By 1954, those unreliable methods were mostly replaced by magnetic core memory, which was still rather cumbersome. Undoubtedly, a revolution was started with the invention of a transistor, that soon enabled then-unbelievable miniaturization of electronic memory via solid-state silicon chip technology.
This led to a modern random-access memory (RAM). It is small-sized, light, but quite expensive at the same time. (The particular types of RAM used for primary storage are also volatile, i.e. they lose the information when not powered).
As shown in the diagram, traditionally there are two more sub-layers of the primary storage, besides main large-capacity RAM:
Processor registers are located inside the processor. Each register typically holds a word of data (often 32 or 64 bits). CPU instructions instruct the arithmetic and logic unit to perform various calculations or other operations on this data (or with the help of it). Registers are technically among the fastest of all forms of computer data storage.
Processor cache is an intermediate stage between ultra-fast registers and much slower main memory. It's introduced solely to increase performance of the computer. Most actively used information in the main memory is just duplicated in the cache memory, which is faster, but of much lesser capacity. On the other hand it is much slower, but much larger than processor registers. Multi-level hierarchical cache setup is also commonly used—primary cache being smallest, fastest and located inside the processor; secondary cache being somewhat larger and slower.
Main memory is directly or indirectly connected to the central processing unit via a memory bus. It is actually two buses (not on the diagram): an address bus and a data bus. The CPU firstly sends a number through an address bus, a number called memory address, that indicates the desired location of data. Then it reads or writes the data itself using the data bus. Additionally, a memory management unit (MMU) is a small device between CPU and RAM recalculating the actual memory address, for example to provide an abstraction of virtual memory or other tasks.
As the RAM types used for primary storage are volatile (cleared at start up), a computer containing only such storage would not have a source to read instructions from, in order to start the computer. Hence, non-volatile primary storage containing a small startup program (BIOS) is used to bootstrap the computer, that is, to read a larger program from non-volatile secondary storage to RAM and start to execute it. A non-volatile technology used for this purpose is called ROM, for read-only memory (the terminology may be somewhat confusing as most ROM types are also capable of random access).
Many types of "ROM" are not literally read only, as updates are possible; however it is slow and memory must be erased in large portions before it can be re-written. Some embedded systems run programs directly from ROM (or similar), because such programs are rarely changed. Standard computers do not store non-rudimentary programs in ROM, rather use large capacities of secondary storage, which is non-volatile as well, and not as costly.
Recently, primary storage and secondary storage in some uses refer to what was historically called, respectively, secondary storage and tertiary storage.[1]

Storage

Computer data storage, often called storage or memory, refers to computer components, devices, and recording media that retain digital data used for computing for some interval of time. Computer data storage provides one of the core functions of the modern computer, that of information retention. It is one of the fundamental components of all modern computers, and coupled with a central processing unit (CPU, a processor), implements the basic computer model used since the 1940s.
In contemporary usage, memory usually refers to a form of semiconductor storage known as random-access memory (RAM) and sometimes other forms of fast but temporary storage. Similarly, storage today more commonly refers to mass storage — optical discs, forms of magnetic storage like hard disk drives, and other types slower than RAM, but of a more permanent nature. Historically, memory and storage were respectively called main memory and secondary storage. The terms internal memory and external memory are also used.
The contemporary distinctions are helpful, because they are also fundamental to the architecture of computers in general. The distinctions also reflect an important and significant technical difference between memory and mass storage devices, which has been blurred by the historical usage of the term storage. Nevertheless, this article uses the traditional nomenclature.

Instalation ANTI-VIRUS

Install Kaspersky Internet Security
If you already have Kaspersky Internet Security 2010 installed and need to activate, please read our Kaspersky 2010 Activation page.
Before you begin:
Please make sure you have removed your previous security software (including prior versions of Kaspersky) in the Control Panel before installing Kaspersky.
If you need help removing the previous security programs, please check our list of removal tools for conflicting software.
If you are installing using the Kaspersky Internet Security 2010 CD, please skip to Step 2.
If you have purchased online, follow Step 1 to download your software.
Step 1 - Save the Installation File:
If you have Dial-Up Internet, we suggest you wait for the Backup CD to arrive to install.
Click the download link provided in your order email to begin. If the link has expired, you can download from our Kaspersky Internet Security Product Updates page.
You will be asked to Run, Save or Cancel the download. Click Save.

Instalation office 2007

To create a network installation point
Create a folder for the Office source files at an accessible location on the network server. For example:
\\server\share\Office12
Note:
Do not create the network installation point at the root of the server.
Insert the Office CD into your CD drive.
In Windows Explorer, select all the files and folders on the CD. Copy the CD contents to the folder on the network. This location becomes your network installation point.
If you are deploying multiple language versions of Office, copy each language pack you want from the source media to the installation point. When you are prompted to overwrite duplicate Setup files, click No.
In the 2007 Office system, core Setup files are shared among all Office products and language packs. Because these files are identical, there is no reason to overwrite the files. Additionally, by not overwriting Setup files, the network installation point remains online and available to users while you add files.
If you are deploying multiple Office products, copy those files from the CD to the installation point. When you are prompted to overwrite duplicate Setup files, click No.
If you create a Setup customization file (MSP file) for the installation, store the file in the Updates folder at the root of the installation point.
Alternatively, you can use the /adminfile option to specify a Setup customization file on the command line.
If users are installing Office after product updates are released, store those MSP files in the Updates folder.
The amount of space required on the network installation point varies by product and by language. The following table shows space requirements for English versions of the 2007 Office system suites that are typically installed in enterprise organizations. These figures account for both the installed product and the installation files stored in the local installation source.
Microsoft Office Standard 2007
660 MB
Microsoft Office Professional Plus 2007
980 MB
Microsoft Office Enterprise 2007
1 GB
The installation point contains only one copy of the language-neutral core product. Each language that you add requires additional space only for the language-specific components.
For example, the U.S. English and the French versions of Office Enterprise 2007 require approximately 1 GB of space each on the server—more than 2 GB in total. Because the language-neutral components are not duplicated, however, a network installation point that includes both languages requires only about 1.75 GB of space. The amount of disk space that you save increases as you add more languages.
For detailed system requirements for all the products in the 2007 Office system, see 2007 Microsoft Office release system requirements.
Note Unlike previous versions of Microsoft Office products, in the 2007 Office system you do not create an administrative installation point by running Setup with the /a command-line option to extract compressed source files. In the 2007 Office system, all installations occur from the compressed source.
Replicate the network installation point
In most enterprise organizations, the network installation point is the location from which users initially install Office. After Office is installed, users do not typically need to rely on the network source for tasks such as updating, modifying, or reinstalling Office. Setup automatically creates a local installation source on each user's computer. If the local source is corrupted or deleted, however, Setup returns to the original network source to recreate the local source on the user's computer.
Replicating the network source to multiple locations is recommended for the following reasons:
Availability. Creating multiple network installation points (which may or may not be in the same physical location) helps ensure that users always have access to a network source. Ideally, the duplicate network installation points are managed by Distributed File System (DFS) technologies and are transparent to users.
Proximity to users. Many companies have high-speed LAN networks that are connected to other subsidiaries or branch offices by much slower WAN connections. Setting up a duplicate network installation point at the remote locations means that Office source files travel over the slow network connection only once; thereafter, users have access to a network source closer to them.
Consistency. By creating one network installation point with all the customizations you want and then duplicating that installation point as needed, you help ensure that the same configuration is deployed throughout your organization.
Flexibility. If the primary network installation point installs a standard corporate configuration of Office, regional offices can apply additional customizations to the replicated network installation points and customize Office for their unique region-specific requirements.
To specify additional network sources
Start the Office Customization Tool (OCT) by running Setup with the /admin command-line option.
On the Additional Network Sources page, click Add. Enter the path to the location to which you plan to copy the network installation point.
You can add as many additional source locations as you need.
Save the Setup customization file (MSP file) generated by the OCT in the Updates folder at the root of the network installation point.
Copy the entire folder structure of the network installation point to the locations you specified in the Setup customization file.
Users who install Office from any of these network installation points have access to the backup network sources. Setup checks these sources automatically when an alternate source is required.
Secure the network installation point
Follow these recommended best practices to help make the network installation point for Office secure:
Make sure that access to source files is read-only.
The Setup.xml and Package.xml files are digitally signed and cannot be modified.
Save all customization files that you create, including Setup customization files and custom Config.xml files, as read-only.
If you are centralizing log files on the network, make sure that users have read/write access to that location.
Make sure that all users have administrative rights before installing Office; you can accomplish this by using your existing software deployment infrastructure.

Menformat HARDISK

Tips dan Cara Memformat Ulang Hard Disk dan Menginstall Ulang OS Windows atau Linux pada Komputer PC / Laptop - Petunjuk Teknis
Mon, 19/06/2006 - 1:23pm — godam64
Masalah yang bersifat fatal dan parah bisa saja terjadi kapan dan di mana saja tidak memandang merk dan harga komputer pc / laptop anda. Terkadang komputer tidak bisa masuk ke windows akibat banyak hal seperti terkena virus, file booting hilang, bad sector, komputer lambat, komputer sering hang, salah seting dan berbagai masalah lainnya.
Jika berbagai cara sudah anda lakukan dan belum mendapatkan hasil yang memuaskan maka jalan pintas / singkat yang paling baik adalah dengan cara format ulang harddisk / hard drive yang ada di koputer pc / laptop anda. Pada tips ini akan diberikan beberapa langkah mudah yang dapat anda lakukan sendiri tetapi tidak secara mendetail. Bila anda butuh bimbingan anda bisa menanyakan di forum situs organisasi.org ini. Mudah-mudahan saya atau kawan lain dapat membantu anda.
A. Langkah dan Tahap Format Ulang Hard Disk
1. Back up / bekap file penting anda yang ada pada hardisk karena dengan format akan menghapus semua file yang ada di hard disk anda. Jika anda punya cd-rw drive atau dvd-rw drive anda bisa membakar file anda ke dalam cd atau dvd. Cara lain backup adalah dengan flash disk, disket floppy, disket zip, pindah file ke jaringan network lan atau internet pada komputer atau server lain dan lain-lain.
2. Setelah backup selanjutnya adalah membuat windows boot disk / rescue disk pada disket floppy 1.4 MB. Disket ini bertujuan untuk booting langsung ke disket tidak melalui harddisk anda. Istilahnya anda akan menggunakan os microsoft dos yang ada pada disket yang anda buat.
3. Ganti Setting BiosSaat komputer dinyalakan anda harus langsung masuk ke tampilan bios untuk setting pilihan urutan boot. Caranya ketika komputer baru dinyalakan anda menekan dan menahan tombol delete sampai bios muncul di layar monitor komputer anda. Ganti urutan booting dengan urutan pertama floppy disk.
4. Format Hard DiskSetelah bios diganti serta disave anda masukkan disket kemudian restart komputer anda. Nanti komputer anda akan otomatis boot dari disket tersebut dan pilih boot without cd-rom supaya proses booting bisa lebih cepat. Setelah masuk ke command prompt a:\ ketik format c: lalu tekan enter. Disesuaikan dengan jumlah partisi anda yang ada. Jika anda punya partisi 3 buah maka tambah perintah format d: dan format e:. Tips dan cara mempartisi hard disk mungkin bisa anda cari di kotak search di sebelah kiri halaman artikel ini. Jika format telah selsesai beri nama drive tersebut sesuai selera anda. Jika semua beres dan berjalan lancar maka proses format ulang telah selesai. Kini harddisk anda menjadi seperti baru kembali.
B. Langkah dan Tahap Install Ulang OS Windows dan Linux
1. Install Windows 98 / 2000 / ME / XP / Vista / LinuxLangkah pertama dalam mengistall ulang operating system pada komputer pc atau laptop anda adalah booting ulang ke disket anda dan pilih support cd-rom device. Setelah keluar command prompt lalu anda masukkan cd instalasi os anda sesuai selera anda. Kemudian cari drive cd-rom atau dvd-rom anda dengan mengetik d: atau e: dan lain sebagainya sesuai lokasi drive cd atau dvd rom anda. Setelah ketemu anda kemudian cari file setup.exe dengan perintah cdnama folfer untuk masuk ke dalam folder. Perintah cd.. untuk mundur satu folder level. perintah dir atau dir/w atau dir/p untuk melihat list file yang ada pada folder tersebut. Kalau sudah ketemu maka jalankan setup.exe atau install.exe dengan mengetik nama file tersebut lalu tekan tombol enter satu kali saja. Langkah berikutnya anda tinggal mengikuti perintah yang ada pada installasi cd atau dvd os.
2. Setting Settingan Boot pada BiosSetelah install ulang windows atau linux selesai, maka keluarkan disket flopyy 1,4 anda dan masuk kembali ke menu bios setelah restart ulang. Pilih IDE-0 sebagai first boot. Floppy bisa anda seting menjadi boot kedua dan cd-rom menjadi boot ketiga. Anda bebas menentukannya sesuai dengan keinginan anda. Sehabis itu direstart ulang kembali.
3. Install Driver dan SoftwareJika sudah berhasil masuk ke tampilan windows atau linux awal, selanjutnya anda nginstall driver untuk sound card, printer, scanner, kabel data, dan sebagainya sesuai hardware yang ada. Anda harus mencari dan memiliki sendiri driver tersebut. Setiap jenis komputer memiliki driver yang berbeda. Biasanya anda akan diberi cd driver saat anda membeli komputer atau hardware lainnya. Tanpa driver maka peralatan yang terhubung pada komputer laptop atau pc tidak dapat berjalan sebagaimana mestinya.
Selamat mencoba dan semoga berhasil

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