Power of PHP.

PHP...Wait...Wait..Wait...It is not related to horse power or something.
PHP is a computer buzzword that extends as PHP hypertext preprocesser.

Let's get into some of the basic terminologies before getting into the core.

HyperText: Text is what you normally see in MS word,Notepad etc.
But HyperText is something more than a simple text.
In websites you may happen to see text in different fonts,colors and behaviors.
Such text are called HyperText.

HTML : A language used to produce hypertext in your websites.
Expands as HyperText Markup Language(HTML).

PreProcess: As the name rightly indicates it is something that is carried out before processsing.

So as you are aware of terminologies like Preprocess and HyperText lets proceed further.

Getting into PHP HyperText Preprocesser.As the figure rightly shows PHP is a script running in the server that is responsible for some preprocessing before the hypertext is sent to the client.

This power of PHP makes it unavoidable on all of the available servers in internet today.
PHP has the power to generate dynamic webpages instead of generating the traditional static pages.

This article may still sound latin to those who are not aware of some computer concepts.
But feel free to comment and ask your doubts because PHP is really vast.
Lets resolve our differences.
If you are really interested in this you can still learn how to make a php page of your own.

Happy PHPing.

Good programming technique.

An application is a collection of programs. Each and every program has its dependence with that of the other programs in the application.This dependence relation between programs can be thought of as Coupling.

Okay...Now lets move on to tightly coupled and loosely coupled.
When a program is very much dependent on other program it is called tightly coupled.
When a program is less dependent on other program then it is called loosely coupled.

So what type of coupling will a good program need?
Obviously it is the loosely coupled programs that the application needs.
When there is less relation between programs then writing codes and debugging is will be easy.

So next time when you write an application go for loosely coupled programs.
Coupling is inversely proportional to Cohesion.
COHESION!!!
What it is? Go and find out.

IP addressing and subnetting

ISRO questions 2009

These are some of the questions asked in ISRO recruitment exam 2009

1.Questions on Networking IP Classes were asked.
Class A. 1-126
Class B. 128-191
Class C. 192-223

2. SHA-1 is a __________Algorithm
SHA expands as Secure Hash Algorithm
It is an Encryption Algorithm.

3.UTP means Unshielded Twisted Pair.

4.Newton Backward Difference Formula

f(x) @ Pn(x) = fn + sÑfn +	s(s + 1)	Ñ2fn	+ . . . +	s(s + 1) . . . (s + n -1)	Ñnfn
	2!			n!

TCP and UDP

The TCP and UDP operates in the transport layer of the OSI model.

They work on the top of the IP protocol working in the Network layer.
TCP header size-20 bytes
UDP header size-8 bytes

assigned port numbers-0- 1023
registered port numbers-1024-65535
dynamic port numbers- 49152-65535

Nagle's algorithem is used to send several small buffered packets as a single packet.

SPOOLING-OS SPOOFING-Internet

E-mail spoofing is a term used to describe fraudulent e-mail activity in which the sender address and other parts of the e-mail header are altered to appear as though the e-mail originated from a different source.




In Operating Systems,, spooling refers to a process of transferring data by placing it in a temporary working area where another program may access it for processing at a later point in time.


The most common spooling application is print spooling: documents formatted for printing are stored onto a buffer (usually an area on a disk) by a fast processor and retrieved and printed by a relatively slower printer at its own rate. As soon as the fast processor has written the document to the spool device it has finished with the job and is fully available for other processes.

The OS way

Operating System is one of the most interesting part of computer Technology.
Without an operating System there is no question for software development or any of the user interface.

The Big Boss lying under all this operating functions is the KERNEL.

Kernal is nothing but a set of programs lying in the disc the execution of these programs make the operating systems work.
Program Execution
Execution of a program from memory involves the creation of a process(assigning memory to program code and executing it).
Interrupts
The hardware or the application gives the indication about which part of the code has to be executed in the kernel.
Suppose, when we press the "A" key in keyboard then the operating system that is the kernel will receive an interrupt that would allow that to execute the code responsible for displaying "A".
This can be taken as an example for a hardware interrupt.

Memory Management:
It is process managing and allocating memory for various programs that is being executed by the kernel.
Virtual memory: Some application may want the program to always execute at a particular space in the memory.This work is being taken care of virtual memory.
What if the program is not loaded into the memory where it has to be loaded.It is nothing but a Page Fault.
Swapping can be used to overcome this page fault.

Scheduler is a small software program that can control the amount of time a program is executed in a particular memory.
The Scheduler swaps the control between the Kernel and the Program to make sure all the Programs are executed for a considerable amount of time and along with its own priority.
This action is called Context Switching.

Some scheduling techniques

1.FCFS(First come first first serve)
2.Shortest job first done
-Preemptive(Gives way for another)
-Non-preemptive(No way)
3.Priority Scheduling(based on Priority)
Starvation of low priority process
4.Round Robin Scheduling
w.r.t Timer
5.Multilevel Queue Scheduling
Round Robin with Multilevel Queues
6.Mutilevel Feedback Queue Schduling.
Mutilevel queue with Priority for each queue.

So let's learn "What is Caching"?
Cache contains all the frequently accessed data . Such data's are retrieved from the main memory and stored in the cache. The processer checks for the needed data in the cache. If the needed data is not present then the processer gets it from the main memory and stores it in the cache for future use.

Dining Philosopher's problem:


Consider the case where some philosophers had to dine together.
But the problem they have one fork on left and one fork on right.
But the food cannot be eaten with a single fork.So if all the phil's
are going to take the left fork at the same time then no one can eat.


The lack of available forks is an analogy to the lacking of shared resources in real computer programming, a situation known as Concurrency.

That is the shared resources are getting locked with no use for anyone.This results in a deadlock.

Semaphore is a variable count used in the method that controls and restricts access to shared resources for ex:as in the case of dining philosophers problem.

So this dining philosophers problem introduces to three technical Jargons.
CDS
Concurrency
Deadlock
Semaphores
This article will be updated.

All People seem to need data processing.

The OSI (Open Syestem Interconnection) reference model was proposed by ISO (InternetionalStandard Organisation) in 1984.
The standard protocols make use of any of those layers of OSI reference model to establish connection between computers.
The reference layers are
Application layer- Presentation Layer- Session layer- Transport layer-
Network Layer-Data Layer- Physical Layer.
So the Mnemonic is "All People Seem To Need Data Processing".
This has been the only most viewed article in my blog.
Please visit other interesting labels like English and Evolving Etymology.Please do comment to make this blog a better one.
With regards ,
Shyam.

Got this while attending IT Quiz in CIT.



Explain 5-4-3 rule?

In a Ethernet network, between any two points on the network, there can be no more than five network segments or four repeaters, and of those five segments only three of segments can be populated.

What is SVN?

Subversion (SVN) is a version control system initiated in 2000 by CollabNet Inc. It is used to maintain current and historical versions of files such as source code, web pages, and documentation. Its goal is to be a mostly-compatible successor to the widely used Concurrent Versions System (CVS).

Subversion is well-known in the open source community and is used on many open source projects, including Apache Software Foundation, KDE, GNOME, Free Pascal, FreeBSD, GCC, Python, Django, Ruby, Mono, SourceForge.net, ExtJS and Tigris.org. Google Code also provides Subversion hosting for their open source projects. BountySource systems use it exclusively. Codeplex offers access to both subversion as well as other types of clients.

Subversion is also being adopted in the corporate world. In a 2007 report by Forrester Research, Subversion was recognized as the sole leader in the Standalone Software Configuration Management (SCM) category and a strong performer in the Software Configuration and Change Management (SCCM) category.^[1]

Subversion is released under the Apache License, making it free software.

What is a FireWall...Layman's Lang. approach

What is a firewall?

A firewall is software or hardware that checks information coming from the Internet or a network, and then either blocks it or allows it to pass through to your computer, depending on your firewall settings.

A firewall can help prevent hackers or malicious software (such as worms) from gaining access to your computer through a network or the Internet. A firewall can also help stop your computer from sending malicious software to other computers.

Music Editor Tool in Java

Making a music editor tool in java requires jlayer which is a mp3 library used to play mp3 files in java.
jlayer can be downloaded from
http://www.cs.princeton.edu/introcs/faq/mp3/mp3.html

Make use of this and if any one come with good results then let me know.

Bye bloggers,Shyam