How Will I Use an Operating System?

The user interface of an operating system is the portion of the program with which users interact.
The user interface can be

1. Command-line,
2.Menu-driven, and
3.Graphics-based.

A command-line interface requires a user to type the desired response at a prompt using a special command language.

To be an effective user of any command-line software, you must memorize its commands and their exact syntax-no easy task.

A menu-driven interface allows the user to select commands from a list (menu) using the keyboard or a pointing device such as a mouse.

A graphical user interface (GUI):

The trend is away from text-based, command-line interfaces to user-friendly, graphics-oriented environment called a graphical user interface (GUI).

Graphical user interfaces rely on graphics-based software.

Graphic-based software permits the integration of text with high-resolution graphic
image, called icons.

GUI users interact with the operating system and other software packages by using a pointing device and a keyboard to issue commands.

Rather than enter a command directly, the user chooses from options displayed on the screen.

The equivalent of a syntax-sensitive operating system command is entered by pointing to and choosing one or more options from menu or by pointing to and choosing a graphics image, called an icon.

Typically GUI includes some or all of the following parts:

-Icons, which are graphical images that represent items, such as files and directories.
-Agraphical pointer, which is controlled by a pointing device (mouse), to select icons and
commands and move on-screen items.
-On-screen pull-down menus that appear or disappear, controlled by the pointing device.
-Windows that enclose applications or objects on the screen.

GUIs have effectively eliminated the need for users to memorize and enter cumbersome commands.

Type of Processing

A multiprocessing operating system allows the simultaneous execution of programs by a computer that has two or more CPUs. Each CPU can be either dedicated to one program, or dedicated to specific functions and then used by all programs.

Interprocessing, also called dynamic linking, is a type of processing that allows any change made in one application to be automatically reflected in any related, linked application.

Real-time processing allows a computer to control or monitor the performance of other machines and people by responding to input data in a specified amount of time.

Virtual-machine (VM) processing creates the illusion that there is more than one physical machine. VM capabilities permit a computer to run numerous operating systems at one time. VM capabilities are typically used on supercomputers and mainframes.

Virtual memory, also called virtual storage, allows you to use a secondary-storage device as an extension of main memory. Virtual memory resolves the problem of insufficient main memory to contain an entire program and its data.

Major Functions of Operating Systems

The major functions of an OS are:

-resource management,
-data management,
-job (task) management, and
-standard means of communication between user and computer.

The resource management function of an OS allocates computer resources such as CPU time, main memory, secondary storage, and input and output devices for use.

The data management functions of an OS govern the input and output of the data and their location, storage, and retrieval.

The job management function of an OS prepares, schedules, controls, and monitors jobs submitted for execution to ensure the most efficient processing. A job is a collection of one or more related programs and their data.

A job is a collection of one or more related programs and their data.

The OS establishes a standard means of communication between users and their computer systems. It does this by providing a user interface and a standard set of commands that control the hardware.

Typical Day-to-Day Uses of an Operating System

-Executing application programs.
-Formatting floppy diskettes.
-Setting up directories to organize your files.
-Displaying a list of files stored on a particular disk.
-Verifying that there is enough room on a disk to save a file.
-Protecting and backing up your files by copying them to other disks for safekeeping.

How Do Operating Systems Differ?

Operating systems for large computers are more complex and sophisticated than those for microcomputers because the operating systems for large computers must address the needs of a very large number of users, application programs, and hardware devices, as well as supply a host of administrative and security features.

Operating system capabilities can be described in terms of

-the number of users they can accommodate at one time,
-how many tasks can be run at one time, and
-how they process those tasks.

Number of Users:

A single-user operating system allows only one user at a time to access a computer.

Most operating systems on microcomputers, such as DOS and Window 95, are single-user access systems.

A multiuser operating system allows two or more users to access a computer at the same time (UNIX).

The actual number of users depends on the hardware and the OS design.
Time sharing allows many users to access a single computer.
This capability is typically found on large computer operating systems where many users need access at the same time.

Number of Tasks

An operating system can be designed for single tasking or multitasking.

A single tasking operating system allows only one program to execute at a time, and the program must finish executing completely before the next program can begin.

A multitasking operating system allows a single CPU to execute what appears to be more than one program at a time.

Context switching allows several programs to reside in memory but only one to be active at a time. The active program is said to be in the foreground. The other programs in memory are not active and are said to be in the background. Instead of having to quit a program and load another, you can simply switch the active program in the foreground to the background and bring a program from the background into the foreground with a few keystrokes.

Cooperative multitasking in which a background program uses the CPU during idle time of the foreground program. For example, the background program might sort data while the foreground program waits for a keystroke.

Time-slice multitasking enables a CPU to switch its attention between the requested tasks of two or more programs. Each task receives the attention of the CPU for a fraction of a second before the CPU moves on to the next. Depending on the application, the order in which tasks receive CPU attention may be determined sequentially (first come first served) or by previously defined priority levels.

Multithreading supports several simultaneous tasks within the same application. For example, with only one copy of a database management system in memory, one database file can be sorted while data is simultaneously entered into another database file.

Operating System

What Is an Operating System?

An operating system (OS) is a core set of programs that control and supervise the hardware resources of a computer and provide services to other system software, application software, programmers, and users of a computer.

The OS gives the computer the instructions it needs to operate, telling it how to interact with hardware, other software, and the user.

The OS establishes a standard interface, or means of communication, between users and their computer systems.
When you power up a computer, you boot the system.
The booting procedure is so named because the computer "pulls itself up by its own bootstraps" (without the assistance of humans).
When booting the system,

First, a program in read-only memory (ROM) initializes the system and runs a system check to verify that the electronic components are operational and readies the computer for processing.
Next, the operating system is loaded to RAM, takes control of the system, and presents the user with a system prompt or a GUI screen full of options.

Operating System Parts

Operating systems are composed of two major parts:

control programs, and
service program.

Control programs manage computer hardware and resources.
The main program in most operating systems is the supervisor program.

A supervisor program is a control program that is known in some operating systems as the monitor, executive, or kernel.
The supervisor program is responsible for controlling all other OS programs as well as other system and application programs.
The supervisor program controls the activities of all of the hardware components of a computer.


Service programs are external OS programs that provides a service to the user or programmer of a computer.
They must be loaded separately because they are not automatically loaded when the operating system is loaded.
They perform routine but essential functions, such as formatting a disk for use and copying files from one location to another.

Computer language-oriented software includes

language translators such as assemblers, interpreters, and compilers.

Program generators (programs that automatically generate program code), debugging and testing programs.

Utilities are programs that are purchased as separate products; they perform a wide range of functions. This type of software includes products such as

-data conversion programs that convert data from one format to another,
-data recovery programs that restore damaged or accidentally erased data,
-librarians that log and track the locations of disk or tape program files,

-security and auditing programs, and

-merge and sort programs.

Application software refers to programs that allow you to accomplish specific tasks, like creating a document, organizing data, or drawing graphs.

Software acts as a connection, or interface, between you and the hardware.

-Interface is a term that describes how two parts are joined so that they can work together.

-System software and application software provide an interface to the hardware.

Shows the functional relationship among system software, application software, hardware, and a user.

Categories of Software

Knowledge the Rooms in the House

Computer hardware cannot perform alone.

Software refers to the instructions that direct the operations of a computer.

There are two basic types of software:

-system software (controls hardware), and
-application software (performs specific tasks).

System software refers to programs designed to perform tasks associated with directly controlling and utilizing computer hardware.

-It does not accomplish specific tasks for a user, such as creating documents or analyzing data.

-System software includes:

-Operating systems (the most important type of system software),
-Data management software,
-Computer language-oriented software, and
-Utilities that help users perform various functions.

-Data management software includes:

-database and file management programs that manage data for an operating system.
-data center management programs used on large system computers that control program execution, monitor system usage, track system resources and utilization, and bill users accordingly.

Interactive With The System

To interact effectively with a computer, user needs to be knowledgeable in four areas.

1.General software concepts (for example, windows, menus, uploading, and so on)

2.The operation and use of the hardware over which you have control (such as the PC, magnetic
disk, and printer).

3.The function and use of the computer's operating system and/or its graphical user interface
(GUI), both of which provide a link between the user, the computer system, and the various
applications.

4.The specific applications programs you are using

The first three areas are prerequisites to the fourth because you will need a:

• working knowledge of software concepts,
  
• hardware, and
  
• the operating system and/or a GUI
  

before you can make effective use of

• Quicken (accounting),
  
• Harvard Graphics (presentation graphics),
  
• Paradox (database).

COMMUNICATION AND NETWORK CONCEPTS

Evolution of Networking: ARPANET, Internet, Interspace.

Different ways of sending data across the network with reference to switchingtechniques.

Data Communication terminologies: Concept of Channel, Baud, Bandwidth (Hz, KHz, MHz) and Data transfer rate (bps, kbps, Mbps, Gbps, Tbps).

Transmission media: Twisted pair cable, coaxial cable, optical fiber, infrared, radio link, microwave link and satellite link.

Network devices: Modem, RJ45 connector, Ethernet Card, Hub, Switch, Gateway.

Different Topologies- Bus, Star, Tree; Concepts of LAN, WAN, MAN.

Protocol: TCP/IP, File Transfer Protocol (FTP), PPP, Level-Remote Login (Telnet), Internet, Wireless/Mobile Communication, GSM, CDMA, WLL, 3G, SMS, Voice mail, Application Electronic Mail, Chat, Video Conferencing.

Network Security Concepts: Cyber Law, Firewall, Cookies, Hackers and Crackers.

WebPages; Hyper Text Markup Language (HTML), eXtensible Markup Language (XML); Hyper Text Transfer Protocol (HTTP); Domain Names; URL; Protocol Address; Website, Web browser, Web Servers; Web Hosting.