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Thursday, January 26, 2012

Different Functions Of Operating Systems

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Q. Explain Functions of operating system

Functions of Operating System

Following are the main functions performed by Operating System:

1. Process Management

CPU can perform one task at one time. If there are many tasks, operating system decides which task should get the CPU first. Operating system also maintains a queue of jobs for processing one by one.

2. Main Memory Management

Operating system manages memory (RAM)for many running programs. It allocates memory area to different programs. It de-allocates the memory area when a program is terminated. It also manages efficient use of RAM during processing.



3. Secondary Storage Management

Operating system manages secondary storage. It manages the stored files and folders on disk in a proper way.
You can create and save files and folders, edit files, copy files, move files from one location to another within one computer or from computer to computer, and delete files and folders etc, with the help oif operating system.

4. I/O System management

It manages Input/output operations. It controls I/O devices like mouse, keyboard, monitor and printer etc.

5. File Management

It manages files, for example:
  • creation of files
  • deletion of files
  • copying of files.
  • editing files
  • moving of files etc.

6. Protection System

There are many processes of different users in memory at a time. So operating system provides protection so that no process can interfere with another process activity. Operating system makes sure that each and every process performs within its own boundaries.

7. Networking

Operating system provides access to shared resources by networking system. Users can share files and hardware resources like printer.

8. Command Interpreter system

Operating system provides command interpreter for reading and executing user commands. For example, Microsoft Windows XP provides Command Prompt to enter and execute commands.

9. Booting

Operating system starts the computer. It checks the computer and makes it ready to work.

10. Loading and Execution

Operating system provides the facility to load programs in memory easily and then execute it.

11. Data Security

Operating system protects the data stored on the computer from illegal use, modification or deletion.

12 Device Controlling

Operating system controls all devices attached to computer with the help of device drivers. Device driver is a software that permits a computer system to communicate with a device. e.g., device driver software for a modem comes with it on CD. We have to install device driver before using a device.

13. Printing Controlling

Operating System also controls printing function. If a user issues two or more print commands at a time, it manages print queue for printing each document one by one in a proper sequence.

14. Providing Interface

Operating system provides User interface to interact with the computer. User Interface may be Graphical user interface (GUI) or Command line interface. For example, Microsoft Windows XP provides an easy to use graphical user interface called GUI. Whereas DOS provides a Command Line Interface called CLI.
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Monday, January 23, 2012

Components of Operating System

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Q. What is an Operating System? Explain Components of an Operating system.

Operating System

An operating system is a set of programs that manages all computer components and operations. Some popular operating systems are DOS, windows, Unix, Linux, and OS/2.
Without Operating System, a computer cannot do anything. Users interact with the computer through operating system. Operating system acts as an interface between a user and computer hardware.




An Operating system has many components to manage all resources of a computer system as following:

1.    Process Management

CPU can perform one task at one time. If there are many tasks, operating system decides which task should get the CPU first.

2.     Main Memory Management

Operating system manages memory (RAM)for many running programs. It allocates memory area to different programs. It deallocates the memory area when a program is terminated.

3.    Secondary Storage Management

Operating system manages secondary storage. It manages the stored files and folders on disk in a proper way.

4.    I/O System management

It manages Input/output operations. It controls I/O devices like mouse, keyboard, monitor and           printer etc.

5.     File Management

    It manages files for example creation and deletion of files.

6.         Protection System

          There are many processes of different users in memory at a time. So operating system provides protection so that no process can interfere with another process activity.   

7.     Networking

Operating system provides access to shared resources by networking system.

8.     Command Interpreter system

Operating system provides command interpreter for reading and executing user commands.
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Attributes of TR Tag in HTML Tables

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Use Of TR Tag




<TR> tag is used to create rows in HTML Tables. <TR> is the opening tag to start a row and </TR> is a closing tag to end a row. You can place pairs of <td>...</td> tags to create data cells in a row within the <tr>...</tr> tags.
for example to create a row with only one cell containing data "Apples", we will use the following html code.and Mangoes respectively:
<tr>
<td>Apples</td>
</tr>
Apples
If you want to create a row with two cells containing data "Apples" and "Mangoes" respectively, we will use the following html code.
<tr>
<td>Apples</td>
<td>Mangoes</td>
</tr>
Apples Mangoes
You canm also create a header row with the help of <TR> tag and <TH> tags. For example, to create a header row with two header cells with contents "Employee" and "Salary", we will use the following HTML coding:
<tr>
<th>Employee</th>
<th>Salary</th>
</tr>
Employee Salary

Attributes of TR Tag

1. align


It is used to define the horizontal alignment of text in cells, in a particular row. The possible values are:
left: The text is aligned to the left.
center: The text is centered.
right: The text is aligned to the right.
justify: The text is justified to both, left and right, margins.
Example HTML code
<table border="1">
<tr align="right">
<td width="100">Salary</td>
<td width="100">10000</td>
</tr>
</table>
Salary 10000

2. valign

It defines vertical alignment of the text with in cells in a row. Possible values are:
    top: The text is aligned to the top.
    middle: The text is vertically centered. This is the default value.
    bottom: The text is aligned to the botom.
  

3. bgcolor

It defines the background color that will be used as background of all the cells inside the row.
For example, if we use <tr bgcolor="green">, all cells in this row will have a green background as shown below.
<table border="1">
<tr bgcolor="green">
<td>Apple</td>
<td>Banana</td>
<td>mango</td>
</tr>
</table>
Apple Banana mango
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Sunday, January 22, 2012

Attributes of Table Tag

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Table Tag Attributes

  1. Border: It is used to specify a border and its thickness for a table.
  2. Cellspacing: It is used to specify the distance between adjacent cells in a table.
  3. Cellpadding: it is used to specify the distance between a cell and cell contents in a table.
  4. Width: It is used to specify width of a table in pixels or as percentage to screen width.
  5. Align: It is used to specify the horizontal alignment of a table. Possible horizontal alignment values are "left", "right" or "center".
  6. Valign: It is used to set the vertical alignment of a table as "top", "bottom" or "middle".
  7. Bgcolor: It sets the background color of a table. You can specify color names or hex values for the color.

    Example of table with border=1, width=200 and align=center attributes

    HTML Coding:

    <table border="1" width="200" align="center">
    <tr>
    <th>Book</th><th>Price($)</th>
    </tr>
    <tr>
    <td>Visual Basic</td><td>75</td>
    </tr>
    <tr>
    <td>C++</td><td>45</td>
    </tr>
    </table>

    BookPrice($)
    Visual Basic75
    C++45

    Example of table with border=5, cellpadding="10" and cellspacing="10"

    <table border="5"  cellpadding="10" cellspacing="10">
    <tr>
    <th>Book</th><th>Price($)</th>
    </tr>
    <tr>
    <td>Visual Basic</td><td>75</td>
    </tr>
    <tr>
    <td>C++</td><td>45</td>
    </tr>
    </table>
    BookPrice($)
    Visual Basic75
    C++45

     Example table with border="5" width="300" bgcolor="yellow"

    <table border="5" width="300" bgcolor="yellow">
    <tr>
    <th>Book</th><th>Price($)</th>
    </tr>
    <tr>
    <td>Visual Basic</td><td>75</td>
    </tr>
    <tr>
    <td>C++</td><td>45</td>
    </tr>
    </table>

    BookPrice($)
    Visual Basic75
    C++45
    Read More...

    Friday, January 20, 2012

    Difference between Cellspacing and Cellpadding

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    Cellspacing and Cellpadding are two important attributes of  <Table> tag. As you know <Table> tag is used to create and display tables in HTML documents.

    What is CELLSPACING?

    Cellspacing is an important attribute of <Table> tag in HTML. Cellspacing specifies the spacing between adjacent cells in a table. Consider the following example of an HTML table with cellspacing attribute set to 50.

    Example of Cellspacing use

    <TABLE border="1" cellspacing="30">
    <th>Name</th><th>Marks</th>
    <tr><td>Sajid Mahmood</td><td>666</td>
    <tr><td>Majid Karim</td><td>555</td>
    </table>

    NameMarks
    Sajid Mahmood666
    Majid Karim555

    Example of Cellspacing=15

    <TABLE border="1" cellspacing="15">
    <th>Name</th><th>Marks</th>
    <tr><td>Sajid Mahmood</td><td>666</td>
    <tr><td>Majid Karim</td><td>555</td>
    </table>

    NameMarks
    Sajid Mahmood666
    Majid Karim555

    Example of Cellspacing=0

    <TABLE border="1" cellspacing="0">
    <th>Name</th><th>Marks</th>
    <tr><td>Sajid Mahmood</td><td>666</td>
    <tr><td>Majid Karim</td><td>555</td>
    </table>

    NameMarks
    Sajid Mahmood666
    Majid Karim555

    What is CellPadding?

    Cellpadding is used to specify the distance between a cell contents and its boundaries. For example, consider the following table with cellpadding=0

    Example of Cellpadding=0

    <TABLE border="1" cellpadding="0">
    <th>Name</th><th>Marks</th>
    <tr><td>Sajid Mahmood</td><td>666</td>
    <tr><td>Majid Karim</td><td>555</td>
    </table>

    NameMarks
    Sajid Mahmood666
    Majid Karim555

    Example of Cellpadding=20

    <TABLE border="1" cellpadding="20">
    <th>Name</th><th>Marks</th>
    <tr><td>Sajid Mahmood</td><td>666</td>
    <tr><td>Majid Karim</td><td>555</td>
    </table>

    NameMarks
    Sajid Mahmood666
    Majid Karim555

    Example of Cellpadding=50

    <TABLE border="1" cellpadding="50">
    <th>Name</th><th>Marks</th>
    <tr><td>Sajid Mahmood</td><td>666</td>
    <tr><td>Majid Karim</td><td>555</td>
    </table>

    NameMarks
    Sajid Mahmood666
    Majid Karim555
    Read More...

    Use Of Colspan and Rowspan in Tables HTML

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    Colspan and Rowspan are two important attributes of TD and TH tags used in HTML tables.

    Colspan




    Colspan is an attribute of TD or TH tags used to make data cells and header cells in an HTML table. We can use Colspan to expand / span a cell on many columns. For example, in the following table, the first header cell spans two columns, so here we use <th colspan="2">Marks</th> to get the required result in the displayed html table.

    Marks
    MathsComputer
    10087
    The complete HTML coding is as follows:

    <table border="1">
    <tr> <th colspan="2">Marks</th> </tr>
    <tr> <th>Maths</th><th>Computer</th></tr>
    <tr> <td>100</td><td>87</td> </tr>
    </table>

    Rowspan

    Rowspan attribute is used to expand or span a cell to multiple rows. For example, in the following table example, the first TH cell (Marks) spans on two rows. We use <th rowspan="2">Marks</th> for this purpose.


    Marks
    MathsComputer
    10087

    The complete HTML coding of the table is as follows:
    <table border="1">
    <tr> <th rowspan="2">Marks</th>
    <th>Maths</th><th>Computer</th></tr>
    <tr><td>100</td><td>87</td></tr>
    </table> 
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    Saturday, January 14, 2012

    HTML Table Tag Basics

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    Tables

    Tables are very important to show data in the form of rows and columns. Tables make data more readable and easy to understand. A table consists of rows, columns and cells.

    HTML Tags To Make A Table

    As we know that there are basically three elements in a table, that is, rows, columns and cells. So, there are the following basic tags to create a table in an HTML web page:
    1. <TABLE> tag
    2. <TR> tag
    3. <TD> tag
    4. <TH> tag


     

    <TABLE> Tag

    <Table> tag is used to specify the start of a table. It also specifies some attributes of the table like ALIGN and BORDER attributes etc.
    Example 1: <Table>                    => Table without a border.
    Example 2: <Table border="1">     => Table with a border of width 1.
    Example 3: <Table align="left" border="2">  => A left aligned Table with a border of width 2.

    <TR> Tag

    TR stands for TABLE ROW. As the name shows, <TR> tag is used to create a row in a table. A row is started by <TR> tag and is closed by </TR> tag. There are one or more <TD> or <TH> tags between <TR> and </TR> tags to create cells.

    Example 1: <TR>
                    <TD>1</TD>
                    <TD>Ahmad</TD>
                    </TR>
    Output:

    1 Ahmad

    Example 2:
                  <TR bgcolor="red">
                  <TD>1</TD>
                    <TD>Ahmad</TD>
                   </TR>
    Output
    1 Ahmad


     

    <TD> Tag

    <TD> tag is used to create a cell. TD stands for TABLE DATA. In addition, the number of cells in a row will specify number of columns in a table. The data to be shown in a cell is placed between <TD> and </TD> tags.

    Example 1: <TD>Ahmad</TD>
    Example 2: <TD bgcolor="yellow">345</TD>
    Example 3: <TD width="100">Nasir</TD>

    <TH> Tag

    <TH> tag is used to create a header row in a table. TH stands for TABLE HEADING.One <TH> tag makes one header cell. The data to be shown in header cell is placed between <TH> and </TH> tags.


    Example 1: <TH> Roll No </TH>
    Example 2: <TH bgcolor="yellow">Name</TH>
    Example 3:
    <TR>
    <TH>Roll Number</TH>
    <TH>Name</TH>
    <Th Marks</TH>
    </TR>
    Output:

    Roll Number Name Marks

    A Complete Table Example Code and Output in Browser

    HTML sample CodeOutput in web browser
    <table border="4">
    <tr>
    <th>Roll Number</th>
    <th>Name</th>
    <th>Marks</th>
    </tr>
    <tr>
    <td>1</td>
    <td>Ahmad</td>
    <td>700</td>
    </tr>
    </table>

    Roll Number Name Marks
    1 Ahmad 700


    Read More...

    Saturday, January 7, 2012

    Different Types of Text Formatting Tags in HTML

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    There are many Text formatting tags available in HTML. You can format your text as:
    • Bold Text
    • Italic Text
    • Underline Text
    • Superscript Text
    • Subscript Text



      Let us discuss these formatting tags one by one with example html source code and the output in web browser.

      1. Bold Text

      <b> tag is used for formatting the text as bold text. You place the text within <b> and </b> tags to make it bold.

      2. Italic Text

      <i> tag is used for formatting the text as italic text. You place the text within <i> and </i> tags to make it italic.

      3. Underline Text


      <u> tag is used for formatting the text as underline text. You place the text within <u> and </u> tags to make it underline.

      4. Superscript Text


      <sup> tag is used for formatting the text as superscript text. You place the text within <sup> and </sup> tags to make it superscript.

      5. Subscript Text


      <sub> tag is used for formatting the text as bold text. You place the text within <sub> and </sub> tags to make it subscript.





      HTML Formatting Tags Source Code Examples

      HTML Formatting Tags Output in web browser
      <b>Bold Text</b>
      <i>Italic Text</i>
      <u>Underline Text</u>
      Superscript Example X Squared= X<sup>2</sup>
      Subscript Example X base 2= X<sub>2</sub>

      Bold Text
      Italic Text
      Underline Text
      Superscript Example X Squared= X2
      Superscript Example X base 2= X2
      Read More...

      Sunday, January 1, 2012

      Types Of Headings In HTML

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      HTML Hedings

      Headings in HTML are used to display Titles, Sub-Titles of Sub-Sub-Titles for your web page text. There are six types of headings in HTML. H1 is the largest heading and H6 is the smallest heading. <H1> is opening tag whereas </H1> is the closing tag for the largest heading. The text between <h1> and </h1> will be displayed as the main Title in your web page. Following are the six tags used for six types of headings in HTML.

      1. <H1> ... </H1>
      2. <H2> ... </H2>
      3. <H3> ... </H3>
      4. <H4> ... </H4>
      5. <H5> ... </H5>
      6. <H6> ... </H6>




      The H1 heading is used for main titles. Actually H1 heading will show the text in largest font size. H2 headings is used for Sub-Titles. H2 displays text in smaller font size than H1, H3 displays text of font size smaller than H1 and H2, and so on. H1 is for largest heading in a text page and H6 is for smallest heading.  

      Importance Of Headings in SEO

      Headings are important not only, for specifying Titles and Sub titles in a web page, but they play an important role to enhance Search Engine Optimization of your web page in major Search engines like Google and Yahoo. Search engines use your headings, especially H1 and H2 headings, to index the structure and content of your web pages. Therefore, proper use of headings may improve your web page's search engine optimization.

      Example HTML Code and Output

      HTML Code for Six HeadingsOutput in Web browser
      <h1>First Heading</h1>
      <h2>Second Heading</h2>
      <h3>Third Heading</h3>
      <h4>Fourth Heading</h4>
      <h5>Fifth Heading</h5>
      <h6>Sixth Heading</h6>


      First Heading

      Second Heading

      Third Heading

      Fourth Heading

      Fifth Heading
      Sixth Heading


      Read More...

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