Follow via:: RSS; Email Alert

operating system

998 Results

Dictionary

operating system

The computer's master control program. When the computer is turned on, a small "boot program" loads the operating system. Although additional system modules may be loaded as needed, the main...

Full Definition »

Dictionary

Definition: operating system

The computer's master control program. When the computer is turned on, a small "boot program" loads the operating system. Although additional system modules may be loaded as needed, the main part, known as the "kernel" resides in memory at all times.

The operating system (OS) sets the standards for all application programs that run in the computer. Applications "talk to" the operating system for all user interface and file management operations. Also called an "executive" or "supervisor," an operating system performs the following functions.

User Interface
All graphics based today, the user interface includes the windows, menus and method of interaction between the user and the computer. Prior to graphical user interfaces (GUIs), all operation of the computer was performed by typing in commands. Not at all extinct, a command-line interface is included in all major operating systems, and certain highly technial operations must be executed from the command line.

Operating systems may support optional interfaces. Although the overwhelming majority of people work with the default interface, different "shells" offer variations of appearance and functionality. See GUI, shell and skin.

Job Management
Job management controls the order and time in which applications are run and is more sophisticated in the mainframe environment where scheduling the daily work has always been routine. IBM's job control language (JCL) was developed decades ago for that purpose. In a desktop environment, batch files can be written to perform a sequence of operations that can be scheduled to start at a given time.

Task Management
Multitasking, which is the ability to simultaneously execute multiple programs, is available in all operating systems today. Critical in the mainframe and server environment, applications can be prioritized to run faster or slower depending on their purpose. In the desktop world, multitasking is necessary for keeping several applications open at the same time so users can bounce back and forth among them. See multitasking.

Data Management
Data management keeps track of the data on disk and other storage devices. The application program deals with data by file name and a particular location within the file. The operating system's file system knows where the data are physically stored (which sectors on disk) and interaction between the application and operating system is through the programming interface (API). Whenever an application needs to read or write data, it makes a call to the operating system (see API).

Device Management
Device management controls peripheral devices by sending them commands in their proprietary command language. The software routine that deals with each device is called a "driver," and the OS requires drivers for the peripherals attached to the computer. When a new peripheral is added, that device's driver is installed into the operating system. See driver.

Security
Operating systems provide password protection to keep unauthorized users out of the system. Some operating systems also maintain activity logs and accounting of the user's time for billing purposes. They also provide backup and recovery routines for starting over in the event of a system failure.

History
The earliest operating systems were developed in the late 1950s to manage tape storage, but programmers mostly wrote their own I/O routines. In the mid-1960s, operating systems became essential to manage disks, complex timesharing and multitasking systems.

Today, all multi-purpose computers from desktop to mainframe use an operating system. Consumer electronics devices increasingly use an OS, whereas in the past, they used custom software that provided both OS and application functionality (see embedded Linux).

Common Operating Systems
The primary operating systems in use are Windows (7, Vista and XP), Macintosh OS X, the many versions of Linux and Unix, IBM i (stemming from the midrange AS/400) and z/OS (IBM mainframes). DOS is still used for some applications, and there are many other special-purpose operating systems.

The mobile world of smartphones and tablets includes Apple's iOS, Google's Android, BlackBerry's QNX, HP's webOS and Microsoft's Windows Phone 7.

System and Application Software
This diagram shows how the major system software interacts with applications in memory. System software comprises the programs that support the running of applications (operating system, DBMS, TP monitor and access methods).

Drivers and Peripherals
This diagram shows the interaction between the operating system, the drivers and the peripheral devices.

Operating System and Application Software
This diagram shows the components of the operating system and typical application programs that run in a desktop computer.

THIS DEFINITION IS FOR PERSONAL USE ONLY
All other reproduction is strictly prohibited without permission from the publisher.
© 1981-2010 The Computer Language Company Inc. All rights reserved.