OPERATING SYSTEM

INTRODUCTION :- An operating system has two parts : Kernel and Shell. The kernel is responsible for interacting with hardware and shell is responsible for interacting with user. The shell acts as the command interpreter which takes the commands from the user, interprets them and then take action accordingly.

GUI (Graphical User Interface) based operating systems have shells that offer graphical elements for interaction.

WINDOW 7 OPERATING SYSTEM

Microsoft window 7 is a GUI operating system that adheres to the features of a good GUI. Multiple applications can be simultaneously run in different window. Apart from this multi-tasking (i.e. simultaneously running multiple applications), a number of concepts and terms are available in window and that is what we are going to briefly discuss here in this section.

The windows operating system uses both mouse and keyword as input devices. Interaction with windows or a windows application is most efficient when options are chosen with mouse and characters are entered via the keyboard.

While working with mouse 

•   Point and click the left button to select an item. A selected item is highlighted in some way. Selection  of an item does not result in the initiation of a process 
•   Point and double click left mouse button to choose an item. When you choose an item, some kind of action occurs.  
•    Right click (press and release the right mouse button once) to display the shortcut menu. A shortcut menu is a menu that shows the most frequency used commands for that selected file or folder for which the mouse has been right clicked.
•    Point and drag (press mouse button and while pressing move to another location and then release the mouse button) to move or resize a window on the display screen.

While working with the keyword 

     Ø  Activate the current menu box by tapping the ALT key.

     Ø  Enter the underlined letter of the menu option in the active menu to choose that option.

     Ø  Arrow keys may be used to highlight menu options.

     Ø  Shortcut keys ( a key or a key combination e.g. Alt + f4 for closing an application) can be used to issue commands within a particular application without activating a menu.

WINDOW FEATURES

Window is one of the moist popular GUI operating system of today’s world. It has got some very useful features that add to its user-friendliness. Let us see about them one by one.

     (a)    THE DESKTOP

fig (a). The Desktop

     The worlds desktop has been derived from real life desk top where a manager puts all the things required by her. For instance on a desktop there may be a pen-stand, note pad, calculator, file folder etc lying which are required by the manager. The desktop of a window also serves the same purpose

In window operating system, the screen upon which icons, windows etc are displayed is known as desktop. The window operating system desktop may contain a background, one or more active or inactive windows, a taskbar and icons as shown in fig. A background can be anything from a single colour screen to an elaborate artistic image. All windows and icons are superimposed on the background whatever it may be.

THE WINDOW

A window is a typical rectangular area pertaining to an application or a document of a dialog. Fig shows application and document window and next fig shows a dialog window.

VARIOUS TYPES OF WINDOW APPLICATIONS AND DOCUMENT WINDOWS

Let us discuss each of these window types in details.

(i)                  THE APPLICATION WINDOW :- An application window contains an open application i.e. a running application such as word or paint. Several applications can be open or running simultaneously, but there is only one active window at any given time

An application window has many elements : the title bar, the menu bar, the workspace, the scroll bar and the corners and borders. Each of these is being described in the following lines.

Fig. The Application Window

THE TITLE BAR

It is the topmost horizontal bar of each application window and it contains the title of the open window. Apart from the title, it has several other elements also viz. application icon, active file name minimize button, maximize/restore button and exit button.

It is the icon representing the open application. When you click at application icon, a pull down control menu appears which is also called system menu. Control menu options vary depending upon the type of application being displayed in the window.

THE MENU BAR

The menu bar for an application window is a horizontal bar just below the title bar. The menu bar lists the menus available for that application. Choosing an option from the menu bar results in pull down menu.

THE WORKSPACE

This is the area in a window below the title bar and menu bar. Everything that relates to the current application is displayed in the workspace.

THE SCROLL BAR

Depending upon the size of a window, the entire application may not be visible. When this happen, the window is outfitted with vertical and/or horizontal scroll bars. Each scroll bar contains a scroll box and two scroll arrows. Keyboard movement keys and mouse can be used to move scroll box up/down or left/right on a scroll bar to display other parts of the application.

CORNERS AND BORDERS

To resize a window, use the mouse and point to a window’s border or corner. The mouse currently changes to a double arrow when positioned over a border or corner. Drag the border or corner in the direction indicated by the double arrow to the desired shape.

2. THE DOCUMENT WINDOW

The document window are the windows within an application window. These afre displayed in the parent application window’s workspace. There can be multiple document windows open in the application window.

THE ICONS

As you know, icons are the preety pictures representing windows elements like files, folder, shortcuts etc. icons play a very important role in graphical user interfaces. Commonly used icons are : application icons, shortcut icons, document icons and disk drive icons

Let us see what these are :

APPLICATION ICONS

These are the graphic renderings of the software package’s logo. If you double click over this icon, the related application gets invoked.

SHORTCUT ICONS

These are little graphics pointing to a particular application, document or folder etc. By double clicking over the them the concerned application/document/floder etc becomes active.

DOCUMENT ICONS

The active document window, ehich is a window within an application window, can be minimized to a document icon. Point and double click on the document icon to restore the document window.

DISK DRIVE ICON

The disk drive icons graphically represent five disk drive options : floppy disk, hard disk, network, CD-ROM/DVD drive, pen drives

Typically PCs have only one or two floppy drives assigned to A and B and hard disk drives are named as C onwards.

  

TYPES OF COMPUTER

Fig. 1. Types of Computers

We have three types of computer. These are

    1.    Digital Computer    2. Analog Computers        3. Hybrid Computer

                  

1. DIGITAL COMPUTERS:-

  
 The digital computers works upon discontinuous data. They convert the data into digits (binary digits 0 and 1) and all operations are carried out on these digits at extremely fast rates. Digital computers are much faster than analog computers and far more accurate. Computers used for business and scientific applications are digital computers. Digital computers can further be classified in two ways :

    (a) Purpose wise digital computers are classified into two types:-

(i)         SPECIAL PURPOSE COMPUTER :- it is the one that is designed to perform a specific task. The instructions (programs) to carry out the task are permanently stored in the machine. For the specific tasks, this type of computer works efficiently but such computers are not versatile.

Fig. 2 specific purpose computer

(ii)              GENERAL-PURPOSE COMPUTERS:- It is the one that can work on different types of programs input to it and thus be used in countries applications. The programs are not permanently stored but are input at the time of execution. These computers are very versatile.

fig.3 General purpose computer

(b)  SIZE AND PERFORMANCE WISE DIGITAL COMPUTERS:- it can be classified into two categories :

(i)              EMBEDDED COMPUTERS:- computers exist in a wide range of sizez and power. The smallest are embedded within the circuitry of appliance such as televisions, washing machines and wrist watches. These computer are typically preprogrammed for a specific task such as tuning to a particular television frequency or keeping accurate time.

Fig. 4 Embedded Computer

(ii)              MICROCOMPUTER:- A microcomputer is a computer whose CPU is a microprocessor. A microprocessor is a processor whose all components are on a single integrated circuit chip. Those are normally single-microprocessor, single-user systems designed for performing basic operations like educational, training, small business applications etc.

Three major categories of microcomputers :-

(a)  PDAs OR PROGRAMMABLE COMPUTERS :- Programmable computers may vary in their computational power, speed, memory and physical size. The smallest of these computers can be held in one hand and are called Personal Digital Assitants (PDAs). 

Fig.5. Programmable Computer

 (b)LAPTOP (NOTEBOOK) COMUTERS AND DESKTOP PERSONAL COMPUTERS :- these  are typically used in businesses and at home to communicate on computer networks for word processing to track finances and to play games. They have large amount of internal memory to store hundreds of programs and documents. They are equipped with a keyword; a mouse, track ball and other pointing devices. Laptop computers usually have similar hardware and software as PCs but they are more compact have flat, lightweight LCDs instead of video display monitor. Laptop computers can be carried out in brief cases. Laptop computer are so called as they can sit on  a lap and desktop computer are  so called as they can sit on a desk.

Fig.6. Laptop

 (c)   WORKSTATION:- workstations are similar to personal computers but have greater memory and more extensive mathematical abilities and they are connected to other workstations or personal computers to exchange data.

Fig.7. Workstation

(iii)     MINICOMPUTER:- minicomputer also called mid-range servers, are more powerful computers than micro computer in terms of processing power and capabilities. Minicomputers are mainly multiuser systems where many users  simultaneously work on the systems. Mi-n+icomputers posses greater storage capacity and larger memory as compared to microcomputers. These are even capable of handling more input-output devices.
 Examples are PDP-11, VAX, 7500 MAGNUM etc.

       (iv)        MAINFRAME COMPUTER :- These are designed to handle huge volumes of data and information. These can support more than hundred users at same time. These are very algre and expensive computers have great processing speeds and very large storage capacity and memory as compared to minicomputers. These computers even possess and work with more than one processor at the same time. Thus one can say these are multiuser, multiprocessor systems. For mainframe computers very sophisticated operating systems are needed to control and supervise their operation.

Example are :- ICL 39, CDC 6600, VAX 8842, IBM 3090/600, IBM4381.

(v)         SUPERCOMPUTER :- Super computer are the most powerful computers among digital computers. These consist of several processors running together thereby making them immensely faster and powerful. These computers are capable of handling huge amount of calculations that are beyond human capabilities. Super computer can perform billions of instructions per second. Some of the today’s super computers have the computing capabilities equal to 40,000 micro computers. These are mainly used in applications like weather forecasting,nuclear science research,seismology, metrology etc.

Examples are :- CRAY X-MP-14, CDC-205, ETA GF-10, FUJITSU VP-400, NEC SX-2 etc

2        ANALOG COMPUTERS:-  In analog computers, continuous quantities are used. Computations are carried out with physical quantities such as voltage, length, current, temperature ate. The devices that measure such quantities are analog devices. E.g. voltmeter, ammeter. Analog computers operate by measuring rather than counting. The main advantage of analog computers is that all calculations take place in parallel and hence these are faster but their accuracy is poor as compared to digital computers. Analog computers are mostly used in engineering and scientific applications. An electronic weighing scale is an example of analog computers.

3.     HYBRID COMPUTERS :- Hybrid computers utilize the best qualities of both the digital and analog computers. In these computers some calculations take place in analog manner and rest of them take place in digital manner. Hybrid  computers are best used in hospital where analog part is responsible for measurement of patient’s heart beat, blood pressure, temperature and other vital signs and then the operation is carried out in digital fashion to monitor patient’s vital signs. Hybrid computers are also used in weather forecasting.

Analog and hybrid computers perform specialized tasks but the digital computers are used almost everywhere in business and scientific applications.