Braille is a writing system used by visually impaired and it is named after Louis Braille, the French man who invented it. The Braille system uses a set of raised bumps or dots that can be felt with a finger.
Braille writing system consists of raised dots arranged in “cells.” A cell is made up of six dots that fit under the fingertips, arranged in two columns of three dots each. Each cell represents a letter, a word, a combination of letters, a numeral or a punctuation mark.
Even after all this time
The Sun never says to the Earth,
“You Owe Me”
And look what happens with a love like that
It lights the whole sky.
What is a BLOb?
BLOb, Binary Large OBject : is a collection of binary data stored as a single entity in a database management system. Blobs are typically images, audio or other multimedia objects. Database support for blobs is not universal. Blobs were originally just big amorphous chunks of data invented by Jim Starkey at DEC(Digital Equipment Corporation)
The four BLOB types are
- TINYBLOB : A BLOB column with a maximum length of 255 (28 – 1) bytes. Each TINYBLOB value is stored using a one-byte length prefix that indicates the number of bytes in the value
- BLOB : A BLOB[(M)] column with a maximum length of 65,535 (216 – 1) bytes. Each BLOB value is stored using a two-byte length prefix that indicates the number of bytes in the value.
An optional length M can be given for this type. I
- MEDIUMBLOB : A BLOB column with a maximum length of 16,777,215 (224 – 1) bytes. Each MEDIUMBLOB value is stored using a three-byte length prefix that indicates the number of bytes in the value.
- LONGBLOB : A BLOB column with a maximum length of 4,294,967,295 bytes or 4GB (232 – 1). Each LONGBLOB value is stored using a four-byte length prefix that indicates the number of bytes in the value.
What is AJAX?
AJAX’s most unique characteristic, is its “asynchronous” nature, which means it can do all of this without having to refresh the page. This lets you update portions of a page based upon user events.
With AJAX you can
- Update a web page without reloading the page
- Request data from a server – after the page has loaded
- Receive data from a server – after the page has loaded
- Send data to a server – in the background
Steps of AJAX Operation
- A client event occurs.
- An XMLHttpRequest object is created.
- The XMLHttpRequest object is configured.
- The XMLHttpRequest object makes an asynchronous request to the Webserver.
- The Webserver returns the result containing XML document.
- The XMLHttpRequest object calls the callback() function and processes the result.
- The HTML DOM is updated.
- abort(): Cancels the current request.
- open(method, URL, async, userName, password): Specifies the method, URL, and other optional attributes of a request.The method parameter can have a value of HTTP methods “GET”, “POST”, “HEAD”, “PUT” and “DELETE”.
- send(content): Sends the request.
- getAllResponseHeaders(): Returns the complete set of HTTP headers as a string.
- getResponseHeader(headerName): Returns the value of the specified HTTP header.
- setRequestHeader(label, value): Adds a label/value pair to the HTTP header to be sent.
- onreadystatechange: An event handler for an event that fires at every state change.
- readyState: Holds the status of the XMLHttpRequest. Changes from 0 to 4:
0: request not initialized
1: server connection established
2: request received
3: processing request
4: request finished and response is ready
- responseText: Returns the response as a string.
- status: Returns the status as a number. eg. 200: “OK”; 404: Page not found
List of some famous web applications that make use of AJAX.
Google Maps: A user can drag an entire map by using the mouse, rather than clicking on a button.
Google Suggest: As you type, Google will offer suggestions. Use the arrow keys to navigate the results.
Gmail: Gmail is a webmail, built on the idea that email can be more intuitive, efficient and useful.
This is a great poem by Maya Angelou
You may write me down in history
With your bitter, twisted lies,
You may trod me in the very dirt
But still, like dust, I’ll rise.
Does my sassiness upset you?
Why are you beset with gloom?
‘Cause I walk like I’ve got oil wells
Pumping in my living room.
Just like moons and like suns,
With the certainty of tides,
Just like hopes springing high,
Still I’ll rise.
Did you want to see me broken?
Bowed head and lowered eyes?
Shoulders falling down like teardrops.
Weakened by my soulful cries.
Does my haughtiness offend you?
Don’t you take it awful hard
‘Cause I laugh like I’ve got gold mines
Diggin’ in my own back yard.
You may shoot me with your words,
You may cut me with your eyes,
You may kill me with your hatefulness,
But still, like air, I’ll rise.
Does my sexiness upset you?
Does it come as a surprise
That I dance like I’ve got diamonds
At the meeting of my thighs?
Out of the huts of history’s shame
Up from a past that’s rooted in pain
I’m a black ocean, leaping and wide,
Welling and swelling I bear in the tide.
Leaving behind nights of terror and fear
Into a daybreak that’s wondrously clear
Bringing the gifts that my ancestors gave,
I am the dream and the hope of the slave.
- Declarative data binding
- Automatic UI refresh
- Can be added on top of your existing web application without requiring major architectural changes
- Very light weight library
- Assists in dependency tracking between HTML element and the underlying data
How KO works?
Instead of manually tracking, each element of the HTML page that rely on the updated data , it will automatically update the DOM when any changes to the data model occurs.
Knockout is not a replacement of jQuery. KO provides a complementary, high-level way to link a data model to a UI. It doesn’t attempt to provide animation, generic event handling, or AJAX functionality. Knockout is focused only on designing scalable and data-driven UI.
MVVM Design Pattern
Knockout uses a Model-View-ViewModel (MVVM) design pattern in which the model is your stored data, and the view is the visual representation of that data and ViewModel acts as the intermediary between the model and the view.