Perfect Computer Notes

Topic: Different Functions Of Operating Systems What is an Operating System? Operating systems are an important type of system software. They provide a lot of facilities to the users. An operating system can be defined as software that acts as an interface between the end user and the hardware. Computer users can use computer systems that have an OS or operating system installed. For example, Microsoft Windows is a popular PC operating system. What is the Importance of Operating System in Computer? Each computer must have at least one operating system to run other programs. for example, if there is no operating system in your computer, you will not be able to use the computer. When you install an OS like Microsoft Windows on your computer, it displays its GUI that is Windows desktop on startup. Now you can use your computer with the help of graphical user interface elements like icons, menus, shortcuts on your computer screen. Similarly if you wish to install application ...

Topic: Explain Different Components of Operating System 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. An operating system works as an interface between the user and the computer hardware. Examples of Operating Systems 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. Components of an Operating system 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 s...

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 co...

Border: It is used to specify a border and its thickness for a table. Cellspacing: It is used to specify the distance between adjacent cells in a table. Cellpadding : it is used to specify the distance between a cell and cell contents in a table. Width : It is used to specify width of a table in pixels or as percentage to screen width. Align : It is used to specify the horizontal alignment of a table. Possible horizontal alignment values are "left", "right" or "center". Valign : It is used to set the vertical alignment of a table as "top", "bottom" or "middle". 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> ...

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> Name Marks Sajid Mahmood 666 Majid Karim 555 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 K...

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 Maths Computer 100 87 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 row...

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: <TABLE> tag <TR> tag <TD> tag <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. ...