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Monday, July 13, 2009

I/O module

Q. What do you mean by I/O module? What are the two basic functions of an I/O module?
Ans: An I/O module is not simply a set of mechanical connectors that wire a device into the system bus. Rather, the I/O module contains logic for performing a communication function between the peripheral and the bus.



The I/O module has two major functions. These are given below:

  • Interface to the processor and memory via the system bus or central switch.

  • Interface to one or more peripheral devices by tailored data links.
Q. Explain three broad classifications of external or peripheral devices.

Ans: External devices are broadly classified into three categories:


    • Human readable: Suitable for communicating with the computer user. Examples of human – readable devices are video display terminals (VDTs) and printers.

    • Machine readable: Suitable for communicating with equipment. Example of machine readable devices is magnetic disk and tape systems, and sensor and actuators, such as are used in a robotics application.

    • Communication: Suitable for communicating with remote devices. Communication devices allow a computer to exchange data with a remote device, which may be a human – readable device, such as a terminal, a machine – readable device or even another computer.

Saturday, July 11, 2009

HTML

HTML tags


Meaning

Structure tags




Creates a comment.




Enclosed the entire HTML page.




Enclosed the head of the HTML document.




Style information.




The title of the document.




Enclosed the body (text & tags) of the HTML document.

bgcolor= “…”


“#ff0000” hexadecimal number is used.

Or “name of color” is used.




Provides general information about the document.




Script language.



Alternative content when scripting not supported.

Headings




First-level heading.




Second-level heading.




Third-level heading.




Fourth-level heading.




Fifth-level heading.




Sixth-level heading.

Links




Create a link or anchor includes common attributes.

href= “…”


The url of the document.

name= “…”


The name of the anchor.

target= “…”


Identifies the window or location to open the link in.

rel= “…”


Defines forward link types.

rev= “…”


Defines reverse link types.

access key= “…”


Determines the accessibility character.

shape= “…”


Is for use with object shape.

coords= “…”


Is for use with object shapes.

tabindex= “…”


Determines the tabbing order.

onClik


Is an intrinsic event.

onMouseOver


Is an intrinsic event.

onMouseOut


Is an intrinsic event.

Lists





# An orderd (numbered) list. Each of the items in the list begins with .

type= “…”


Specify the numbering scheme to use in the list. Type can a, A, i, I.

start= “…”


Specify at which number to start the list.





# An unordered (bulleted or otherwise-marked) list. Each of the items in the list begins with .

Type= “…”


Specify the bulleting scheme to use in the list (square, circle, disc).




A menu list of items.




A directory listing.

# …


Individual list items in ordered, unordered, menu or directory list. Closing tag () is optional.

Type= “…”


Reset the numbering or bulleting scheme from the current list element. Only applies to

and
lists.

Value= “…”


Reset the numbering in the middle of an ordered

list.





A definition of glossary list




Definition term. Closing tag is optional in HTML but required in XHTML 1.0




The corresponding definition to a definition item. Closing tag is optional in HTML but required in XHTML 1.0

Character formatting




Stronger emphasize text (usually bold).




Text in a smaller font than the text around it.




Code sample.




Text to be typed in by the user.




Sample text.




A definition of a term.




A citation.




Boldface text.




Emphasized text (usually italic).




Italic text.




Underlined text.




Strike-through text.




Bigger print than the surrounding text.




Subscript text.




Superscript text.




Typewriter font.




A plain paragraph;
is optional.





Preformed text.




A variable of placeholder for some other value.




Indicate the abbreviation of a word.





Used for long quotes for citations.




Causes the enclosed text to have a blinking effect.




Designate a word formed by combining the initial word.

,

align= “…”


Left justified, right justified and centered the text within the paragraph or heading.




Div can be used to align heading, paragraph, quotes, images, tables, and so on.

align= “…”


Left justified, right justified and centered all the content between the opening and closing tag.




Centers all the content between the opening and closing tags.

Other elements



A horizontal rule line at the given position in the text. There is no closing tag in HTML for ; for XHTML, add a space forward slash (/) at the end of the tag and its attributes (for example:

).

size= “…”


The thickness of the rule, in pixel.

width= “…”


The width of the rule, either in exact pixels or percentage (%) of page width.

align= “…”


The alignment of the rule on the page. Possible values are left, right and center.

noshade= “noshade”


Display the rule without three dimensional shading

color= “…”


Display the color of the rule.


/>


A line break. There is no closing tag.




Does not wrap the enclosed text.



Wraps the text at this point only if necessary. Add a space and forward slash at the end of the tag.




Signatures or general information about a document’s author.




For space.

"


(“) quotation sign.

à


(a) sign.

«


(«) sign.

©


(©) sign.

<


(<) less than sign.

>


(>) greater than sign.

&


(&) ampersand sign.

&#...;


Digit of number.

Fonts




Change the size, color and family/face of the font.

size= “…”


The size of the font to change to, either from 1 to 7 (default 3) or as a relative number using +N or -N. Relative font sizes are based on the value of .

color= “#ff0000”


The font color.

face= “…”/family= “…”


Font type.




Sets the default size of the font for the current page.

size= “…”


The default size of the font, from 1 to 7.

Tables




Create a table.

align= “…”


Possible values are left, center and right. Determines the alignment of the table.

border= “…”


Width of the border in pixel.

bordercolorlight= “…”


Name of color.

bordercolordark= “…”


Name of color.

cols= “…”


Used to define the attributes of a columns in a table.

cellspacing= “…”


Spacing between cells.

cellpadding= “…”


Spacing in cells.

width= “…%”


Table width.

bgcolor= “#ffffff”


Change the background color of the table.

frame= “…”


Frame attributes are following

void


The default value. No sides of the external borders are visible.

above


Renders only the top side of the border.

below


Renders only the bottom side of the border.

hsides


Renders the top and bottom sides of the border.

lhs


Renders the left hand side of the border.

rhs


Renders the right hand side of the border.

vsides


Renders the right and left sides of the border.

box


Renders all four sides of the border.

border


Renders all four sides of the border.

rules= “…”


Rule attributes are following

none


The default value. No rules are drawn around any of the cells.

groups


Rules will appear between row groups as defined by
, , and and between column groups as defined by , and .




Creates an optional caption for the table.

align= “…”


Align the caption as left, right, and center.

valign= “…”


Vertically align the caption as top, center, and bottom.




Enclosed one or more columns in a group.

align= “…”


Used to set alignment of all cells in a column group. Possible values are left, center and right.




Creates a row group that defines the heading of the table. A table can contain only one heading.

align= “…”


Used to set alignment of the contents in table head. Possible values are left, center and right.




Creates a row group that defines the footer of the table. A table can contain only one footer. Must be specified before the body of the table is rendered.

align= “…”


Used to set alignment of the contents in table foot. Possible values are left, center and right.




Defines one or more row groups to include in the body of the table. Table can contain more than one body section.

align= “…”


Used to set alignment of the contents in table body. Possible values are left, center and right.




Defines a table row, which can contain heading and data cells.

align= “…”


The horizontal alignment of the contents of the cells within this row; possibly values are LEFT, RIGHT, CENTER and JUSTIFY.

valign= “…”



The vertical alignment of the contents of the cells within this row; possibly values are TOP, MIDDLE, BOTTOM and BASELINE.

bgcolor= “#ffffff”


Change the background color of the row.






Defines a table cells that contain a heading. Heading cells are usually indicated by boldface and centered both horizontally and vertically.

align= “…”


The horizontal alignment of the content of the cell.

valign= “…”


The vertical alignment of the content of the cell.

rowspan= “…”


The number of rows this cell will span.

colspan= “…”


The number of columns this cell will span.

nowrap= “…”


Do not automatically wrap the contents of this cell.

bgcolor= “#ffffff”


Change the background color of the cell.

width= “…%”


Table width.






Defines a table cell containing data. Table cells are in regular font and are left-aligned and vertically centered within the cells.

align= “…”


The horizontal alignment of the content of the cell.

valign= “…”


The vertical alignment of the content of the cell.

rowspan= “…”


The number of rows this cell will span.

colspan= “…”


The number of columns this cell will span.

nowrap= “…”


Do not automatically wrap the contents of this cell.

bgcolor= “#ffffff”


Change the background color of the cell.

width= “…%”


Cell width.

width= “…%”


Cell width.

Images



Inserts an inline image into the document; includes common attributes.

src= “…”


The URL of the image.

alt= “…”


A text string that will be displayed in browsers that can not support image.

ismap


This image is a serve side-image map.

usemap


This image is a client side-image map.

align= “…”


Determines the alignment of the given image.

“top”


Align the top of the image with the topmost part of the line.

“middle”


Align the center of the image with the middle of the line.

“bottom”


Align the bottom of the image with the bottom of the line of text.

height= “…”


Is the suggested height in pixels.

width= “…”


Is the suggested width in pixels.

vspace= “…”


The space between the image and the text above or bellow it.

hspace= “…”


The space between the image and the text to its left or right.

Frames




Define a frameset.

rows= “…”


Number of rows in frame.

cols= “…”


Number of columns in frame.

onLoad= “…”


Is an intrinsic event.

onUnload= “…”


Is an intrinsic event.




Create a frame.

name= “…”


Is the name of target frame.

src= “…”


Calls the frame content source.

frameborder= “…”


Determines the frame border.

marginwidth= “…”


Defines margin width.

marginheight= “…”


Defines margin heights.

noresize= “…”


Determines ability to resize frames.

Scrolling= “…”


Determines ability to scroll within frames.




Defines an inline frame.




Alternate content when frames not supported.

Style Sheet

css


Cascading Style Sheet




Style information.