Functions Of An Operating System Part 2 of 3|Operating Systems Basics

This article is started in the middle. You should see the Functions Of An Operating System Part I before you read this

Managing and Monitoring Resources and Jobs

As you work on your computer, the operating system continuously manages your computer’s resources (such as software, disk space, and memory) and makes them available to devices and programs when they are needed. If a problem occurs—such as a program stops functioning or too many programs are open for the amount of memory installed in the computer—the operating system notifies the user and tries to correct the problem, often by closing the offending program. If the problem cannot be corrected by the operating system, then the user typically needs to reboot the computer.

As part of managing system resources, the operating system schedules jobs (such as documents to be printed or files to be retrieved from a hard drive) to be performed using those resources. Scheduling routines in the operating system determine the order in which jobs are carried out, as well as which commands get executed first if the user is working with more than one program at one time or if the computer (such as a server or mainframe) supports multiple users.

File Management

                                                                       
Another important task that the operating system performs is file management—keeping track of the files stored on a computer so that they can be retrieved when needed. You can organize the files on a storage medium into folders to simplify file management. Usually the operating system files are stored inside one folder (such as a Windows folder), and each application program is stored in its own separate folder inside a main programs folder (such as Program Files). Other folders designed for storing data files are typically created by the operating system (such as the Documents (or My Documents) and Music (or My Music) folders in Windows, depending on the version of Windows being used); individuals may create additional folders, as desired, to keep their files organized. Folders can contain both files and other folders (called subfolders).

Files and folders are usually viewed in a hierarchical format; the top of the hierarchy for any storage medium is called the root directory. The root directory typically contains both files and folders. To access a file, you generally navigate to the folder containing that file by opening the appropriate drive, folder, and subfolders. Alternatively, you can specify the path to a file’s exact location.

C:\ Documents\ Letters\ Mary

leads through the root directory of the C drive and the Documents and Letters folders to a file named Mary. A similar path can also be used to access the files John and Bill. You specify a filename for each file when you initially save the file on a storage medium; there can be only one file with the exact same filename in any particular folder on a storage medium.

Filename rules vary with each operating system. For instance, current versions of Windows support filenames that are from 1 to 260 characters long (the length includes the entire path to the file’s location) and may include numbers, letters, spaces, and any special characters except / : * ? “ < > and ⎢. Filenames typically include a file extension at the end of the filename. File extensions are usually three or four characters preceded by a period and are automatically added to a filename by the program in which that file was created, although sometimes the user may have a choice of file extensions supported by a program.

File extensions should not be changed by the user because the operating system uses them to identify the program that should be used to open the file. For instance, if you issue a command to open a file named Letter to Mom.docx, the file will open using the Microsoft Word program (assuming a recent version of that program is installed on the computer) because the .docx file extension is associated with the Microsoft Word program. Files can be opened, as well as moved, copied, renamed, and deleted, using a file management program such as Windows Explorer. You may not be able to see file extensions in your file management program, however, since they are typically hidden by default.

DOCUMENTS
.doc .docx .txt .rtf .htm .html
.mhtml .xml .xls .xlsx .mdb. .accdb
.ppt .pptx .pdf .sxc .sxi .odf
PROGRAMS
.com .exe
GRAPHICS
.bmp .tif .tiff .jpg .jpe .jpeg .eps
.gif .png .pcx .svg .dib AUDIO .wav .au .mp3 .snd .aiff .midi
.aac .wma .ra .m4a
VIDEO
.mpg .mp2 .mp4 .mpe .mov .avi
.rm .wmv .wm .asf
COMPRESSED FILES
.zip .sit .sitx .tar

Security

A computer’s operating system can use passwords, biometric characteristics (such as fingerprints), and other security procedures to prevent outsiders from accessing system resources that they are not authorized to access. Most operating systems have other security features available, such as an integrated firewall to protect against unauthorized access via the Internet or an option to download and install security patches (small program updates that correct known security problems) automatically from the operating system’s manufacturer on a regular basis. Operating system passwords can also be used to ensure that administrative level operating system tasks (such as installing programs or changing system settings) are performed only by authorized users.

Processing Techniques for Increased Efficiency

Operating systems often utilize various processing techniques in order to operate more efficiently and increase the amount of processing the computer system can perform in any given time period.

Multitasking

Multitasking refers to the ability of an operating system to have more than one program (also called a task) open at one time. For example, multitasking allows a user to edit a spreadsheet file in one window while loading a Web page in another window or to retrieve new e-mail messages in one window while a word processing document is open in another window. Without the ability to multitask, an operating system would require the user to close one program before opening another program. Virtually all of today’s operating systems support multitasking.

Although multitasking enables a user to work with multiple programs at one time, a single CPU core cannot execute more than one task at one time. Consequently, the CPU rotates between processing tasks, but it works so quickly that to the user it appears as though all programs are executing at the same time.

Multithreading

A thread is a sequence of instructions within a program that is independent of other threads.Examples might include spell checking, printing, and opening documents in a word processing program. Operating systems that support multithreading have the ability to rotate between multiple threads (similar to the way multitasking can rotate between multiple programs) so that processing is completed faster and more efficiently, even though only one thread is executed by a single core at one time. An exception to this is computers using Intel’s Hyper-Threading Technology, which allows more than one thread to be executed by
a single CPU core at one time. Most current operating systems support multithreading.

Continue to Functions Of An Operating System Part 3 of 3