Device Management and Configuration
Another feature of the operating system is control of various I/O devices installed on the computer. Technical control at this level requires interaction between the kernel, device drivers and BIOS. Users can, in some cases, adjust their computer systems precisely by changing the parameters that deterring how the operating system or device drivers are turning to external devices.
Interrupt Control
One of the important tasks of the kernel is handling the interrupts. Interruption is a signal to the processor that there are some events that require immediate attention. Often these events are associated with the Input/ Output operation but there are other types of interrupts. The kernel calculates what caused the interruption, and gives an appropriate response. It should act very quickly. To avoid losing information during the next interrupts, each interruption must be processed in less than a thousandth of a second.
The keyboard interface processor sends a signal called an interrupt request (IRQ).When the processor receives this signal, it ceases to run an application (a web page editor, in our example),recording the address of the last executed command. Than it goes to the keyboard interrupt handler and starts executing commands that are there. Since the processor registers contain all data manipulated by the user application, the interruption handler must save the contents of these registers before he can use the register for his own purposes. The state of the keyboard interface can be seen after saving the register and it is possible to receive the byte of the incoming data. This byte is placed in memory to be tested by the keyboard driver when it works the next time, perhaps in a millisecond. Then, the keyboard interrupt handler restores the saved registers and passes them to the previously performed task control (editing application Web page),resuming execution exactly at the point where it was interrupted. All this happens within a few hundred of microseconds ;the application does not even know that there was an interruption.
Classification of desktop applications.
File organization
One of the main functions of the computer is storing and retrieval on information. Information is stored in one or more «files» which, in turn, an organized in «folders».
Therefore if you create a file called Friends, you can also address it as friends or FRIENDS or even friends. Other operating system the FRIENDS.txt and friends files are different files. Each file also has a related property set. The most important property is the file type which specifies to the operating system what application needs to be used for operation with this file. Other properties include the size of the file, the data and time of the file creation, time when the file was last modified.
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Folders . Files permanently are in folders which sometimes are called directories. Folders have names and properties. And like files, each folder takes its own location: it settles down in another folder called its parent. It provides a file system with hierarchical structure, like a family tree. The peak of a folder hierarchy is called the root.
The file system will not allow two elements to have the same name in the folder. You can check it, having created two files in your working folder with the names file1 and file2. If you then try to change the name file2 to file1, you will get an error message, and the change will not be made.
Devices. Folders are placed on the computer. The computer can have many drives – the disk drive A, the disk drive A, the disk drive D, the device E, etc. The only way to address drives is double clicking the My Computer icon on your Desktop. This icon is usually located in the upper left corner of the desktop. After double clicking on «My computer» icon, you will see that each device is marked with an icon that indicates the type of agent that uses the device. For example, an icon of a hard drive – the image of a hard drive, and an icon of the optical device – the of CD ROM. Clicking on the icon for the will puts you in the root directory of the device.
Shortcut is an alternative path to a file. Shortcuts are named and «live» in folders as well as files. But a shortcut does not actually contain any data Instead, it has the ability to specify the path to the file where you can find data. This file is called the target shortcut. The target can be anywhere, ever on a different device. The shortcut only refers to it; it is not a copy. However, when you open and edit a shortcut, you actually edit the file referenced by the shortcut.
Shortcuts can specify folders as well as files. To create a shortcut, right-click the mouse on icon of the addressee file or folder and select «To create a shortcut» from the pop up menu. Note, that you cannot create a shortcut to another shortcut. If you try to do it, then receive a shortcut to the address of the first shortcut – the same effect, as when copying the first shortcut. Try to create your own shortcut and look at its properties.
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Names and Types of Files. In the original file system of DOS used in early Windows versions, the names of files were restricted to eight uppercase characters plus the three-character extension separated by a point. Sometimes such style of file designation is named style 8.3. Extension Defines file type. For example, the of purchases saved as a text file can be named SHOPPING.TXT while an abstract created as a Microsoft Word document, perhaps would have the name RESUME.DOC. Below is a list of extensions to the basic types of files
Questions:
1. What are the responsibilities of Operating Systems?
2. Define the following with suitable examples.
Single–user OS
Multi-user OS
3. What are utility programs? Define some tasks performed by them.
4. What is meant by library programs?
References
1. June J. Parsons and Dan Oja, New Perspectives on Computer Concepts 16th Edition - Comprehensive, Thomson Course Technology, a division of Thomson Learning, Inc Cambridge, MA, COPYRIGHT © 2014.
2. Lorenzo Cantoni (University of Lugano, Switzerland) James A. Danowski (University of Illinois at Chicago, IL, USA) Communication and Technology, 576 pages.
3. Craig Van Slyke Information Communication Technologies: Concepts, Methodologies, Tools, and Applications (6 Volumes). ISBN13: 9781599049496, 2008, Pages: 4288
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