04Nov/16

Oracle Functions

November 4, 2016RDBMSoracle-functions, sql-functionsDreamMaker

Oracle provides number of in-built functions. Oracle functions can be divided into two broad categories: Scalar functions Scalar functions are those functions that operates on individual row. It can be categories asRead More…

04Nov/16

Aggregate Function

November 4, 2016RDBMSaggregate-functions, oracle-functions, sql-functionsDreamMaker

Aggregate functions are those functions that can be apply on multiple rows and returns signal result for all rows. They are also known as grouping functions. Oracle provides the following aggregate function.Read More…

01Nov/16

Numeric Function

November 1, 2016RDBMSmath-function, numeric-function, oracle-functionsDreamMaker

ABS () It returns absolute value of the given values. Syntax: ABS (Val); Example: SELECT abs (-15) FROM DUAL ; Output: 15 Power () It returns power of Mn where m isRead More…

01Nov/16

Date Function

November 1, 2016RDBMSconversion-function, date-functions, oracle-functionsDreamMaker

Add_Month: It returns date after adding specifies number of months in to the given dates. Syntax: Add_Month (date, month); Example: SELECT add_Month (sysdate, 3) FROM DUAL ; Output: 15-Aug-2016 ; Last_Day: ItRead More…

01Nov/16

Conversion Function

November 1, 2016RDBMSconversion-function, oracle function, sql-functionsDreamMaker

Conversion function are used to convert one data type value into another data type. to_number(): It converts character value in to the numeric data type. Syntax: to_number (char); Example: SELECT to_number (substrRead More…

06Oct/16

String Handling Functions

October 6, 2016RDBMSfunctions, oracle-functions, string-handling-functionsDreamMaker

Upper(): It returns specified string into the upper case. Syntax: Upper(String or Filed); Example: SELECT upper(‘Welcome’) FROM DUAL; // with constant String SELECT upper(firstName) FROM EMP ; // where firstName is aRead More…

27Sep/16

Transaction Control Language Statements (TCL)

September 27, 2016RDBMScommit, rollback, savepoint, tclDreamMaker

Commit: Commit command is used to commit or save transaction permanently. It is similar to a save command of other windows based application. When we apply commit command all the transaction andRead More…

17Sep/16

Creating new table from existing table

September 17, 2016RDBMScreating-new-table, insert-record-from-existing-tableDreamMaker

It is easy to create a new table from the existing table instead of specifying a new structure. It creates a new table with the column specified into the select query. ItRead More…

10Sep/16

IN / NOT IN Clause

September 10, 2016RDBMSin, not-inDreamMaker

IN clause can be use for searching operation. It searches for the records with specific criteria. It displays those records that are matches with the values specified into the IN clause. ItRead More…

29Aug/16

LIKE Predicate (pattern matching)

August 29, 2016RDBMSlike, pattern-matchingDreamMaker

Oracle allows facility to access records that matches specific pattern. It can be helpful when we don’t know the exact form of data that we want to search. Oracle uses “LIKE” predicateRead More…

Structure: An overview

Structure is one of the important concept in C programming language as it offers good functionality and ease of dealing with large data.

In this post we are going to discuss concept of structure and how to deal with when structure is involved in an easy to use manner.

A structure is a user-defined data type.

It can be used to store related data items as a single unit.

A structure is a collection of either similar or different data type items.

It is similar to record that stores related information about an entity.

Structures are similar to arrays which store similar data items and referred by a common name but an array can store only similar data type items while structure can store both similar as well as different data items together.

Structure elements are referred to as structure member.

It can be used to represent complex data items in an easy and more meaningful way.

Since structure is a user-defined data type, it needs to be declared before using it.

We have to tell the compiler what kind of our requirement is and how it can be fulfilled.

We can compare a structure with a structure/plan of house drawn by the engineer on the paper first to build the home.

Plan describes the requirement stated by the owner such as number of floors, total rooms, height, width and length of rooms etc.

Once the plan is ready engineer uses it to build the real house or the building as per the plan.

The same plan can be used to build as many houses as we want each of the same physical shape and structure.

The same concept is applicable in the case of programming.

By declaring a structure, programmer provides a blue print about his/her requirement to the compiler and then after it can be used to create a variable as per the structure definition just like we create a variable of basic data types such as int, float, char.

Compiler allocates memory only when a structure variable is created.

It acts as a template that can be used for creating variables later.

Difference: Structure v/s Array

Array		Structure
1.	An array is a derived data type.	A structure is a user-defined data type.
2.	An array is a collection of similar data type items.	A structure is a collection of different data type items.
3.	Memory for the array will be allocated at the time of its declaration.	Memory is allocated only at the time of structure variable declaration.
4.	Array elements are referred by array index.	Structure elements are referred by its variable name using period sign with structure variable.
4.	It is difficult to represent complex related data using array.	It is easy to represent complex and related data using structure.
5.	Array does not have any special keyword to declare it instead it used [] bracket to define array size along with data type.	*“struct”* keyword is used in structure declaration.
6.	Syntax: data type arr_name [size];	Sytanx : struct struct_name { Type member1 ; Type member2 ; };

For information on how to declare and initialize structure read Structure Declaration.

Hello friends! We often encounter problems related to maths and to deal with it is such a cumbersome task but thankfully not in C programming language as it offers rich set of library functions to deal with mathematical problems.

In this post I will explain some of the basic and most frequently used math handling functions. Note that all the math related functions are written inside <math.h> header file so don’t forget to include it in our program to utilize math functions.

floor( ):

It returns the nearest integer value which is less than or equal to the floating point argument passed to this function.

Syntax:

double floor ( double x );

Example:

#include <stdio.h>
#include <math.h>

void main()
{

   float i=5.1, j=5.9, k=-5.4, l=-6.9;
   printf("floor of  %f is  %f\n", i, floor(i));
   printf("floor of  %f is  %f\n", j, floor(j));
   printf("floor of  %f is  %f\n", k, floor(k));
   printf("floor of  %f is  %f\n", l, floor(l));

}

abs( ):

It returns the absolute value of an integer. The absolute value of a number is always positive. Only integer values are supported in C.

Syntax:

int abs ( int n )

Example:

#include <stdio.h>
#include <stdlib.h>

void main()
{
   int m = abs(200);     // m is assigned to 200
   int n = abs(-400);    // n is assigned to -400
   printf("Absolute value of m = %d\n", m);
   printf("Absolute value of n = %d \n",n);
}

Output:

Absolute value of m = 200   Absolute value of n = 400

round( ):

It returns the nearest integer value of the float/double/long double argument passed to this function.
If decimal value is from ”.1 to .5″, it returns integer value less than the argument.
If decimal value is from “.6 to .9″, it returns the integer value greater than the argument.

Syntax:

Double round(double a);
float roundf (float a);
long double roundl (long double a);

Example:

#include <stdio.h>
#include <math.h>

void main()
{
   float i=5.4, j=5.6;
   printf("round of  %f is  %f\n", i, round(i));
   printf("round of  %f is  %f\n", j, round(j));
}

Output:

round of 5.400000 is 5.000000
round of 5.600000 is 6.000000

pow():

It is used to find the power of the given number.

Syntax:

double pow (double base, double exponent);

Example:

#include <stdio.h>
#include <math.h>

void main()
{
   printf ("2 power 4 = %f\n", pow (2.0, 4.0) );
   printf ("5 power 3 = %f\n", pow (5, 3) );
}

Output:

2 power 4 = 16.000000
5 power 3 = 125.000000

sqrt( ):

It is used to find the square root of the given number.

Syntax:

double sqrt (double x);

Example:

#include <stdio.h>
#include <math.h>

void main()
{
   printf ("sqrt of 16 = %f\n", sqrt (16) );
   printf ("sqrt of  2 = %f\n", sqrt (2) );
}

Output:

sqrt of 16 = 4.000000
sqrt of 2 = 1.414214

C Programming language offers rich set of conversion functions to meet our need. In my last post, we had discussed about some of basic I/O functions.

In this post, we will learn some of the frequently used conversion functions available in <ctype.h> header file.

1. isdigit()

Use:

It is used to check if argument is digit or other character. It returns true if character is digit else false.

Syntax:

 isdigit (char) ;

Example:

isdigit(‘10’)

Output:

true

2. isalpha()

Use:

It is used to check if argument character is alphabet (a to z) or other character. It returns true if character is alphabet and false otherwise.

Syntax:

     isalpha (char) ;

Example:

isalpha(‘A’)

Output:

    true

3. isalnum()

Use:

It is used to check if argument character is alphabet (a to z) or number (0 to 9) or other character. It returns true if character is alphabet or digit and false otherwise.

Syntax:

   isalpha (char) ;

Example:

   isalpha(‘10) ;

Output:

   true

4. isupper()

Use:

It is used to check if character is upper case or not. It returns true if character is upper case and false otherwise.

Syntax:

    isupper (char) ;

Example:

isupper(‘a’) ;

Output:

  false

5. islower()

Use:

It is used to check if character is lower case or not. It returns true if character is lower case and false otherwise.

Syntax:

 islower (char) ;

Example:

islower(‘a’) ;

Output:

 true

6. isspace()

Use:

It is used to check if character is space or not. It returns true if character is space and false otherwise.

Syntax:

 isspace (char) ;

Example:

isspace(‘a’) ;

Output:

false

7. isspunct()

Use:

It is used to check if character punctuation mark or not. It returns true if it is and false otherwise.

Syntax:

ispunct (char) ;

Example:

ispunct(‘!’) ;

Output:

true

8. toupper()
Use:

It is used to convert lower case character to upper case.

Syntax:

toupper (char) ;

Example:

toupper(‘a’) ;

Output:

9. tolower()

Use:

It is used to convert upper case character to lower case.

Syntax:

tolower (char) ;

Example:

tolower(‘A’) ;

Output:

C programming language provides a rich set of Input-Output (I/O) functions to make the I/O operations easily. They are available inside stdio.h header file so we need to include stdio.h into our program to use them.

In this post, we will look into some of the most common I/O functions in detail.

1. getchar()

Use:

It is used to read one character from the standard input device. It is available in <stdio.h> header file.

Syntax:

var = getchar () ;

Example:

char ch = getchar() ;
printf(“\n You entered %c “, ch);

Output:

You entered S

2. getch()

Use:

It is used to read character from the standard input device. It will not echo the character that you are inputting. Computer waits till you enter character from the input device and assigns it to the character variable. There is no need to press enter key when you finish data input. It is available in <conio.h> header file.

Syntax:

var = getch () ;

Example:

char ch = getch() ;
printf(“\n You entered %c “, ch);

Output:

You entered S

3. putchar()

Use:

It is used to write one character on the terminal. It is available in <stdio.h> header file.

Syntax:

putchar (char) ;

Example:

char ch = 'C' ;
putchar(ch);

Output:

Read String Functions.

Today social media serves as the biggest platform as a means of communication globally.

It helps to share your idea, thoughts across the globe.

If you own a business and want to advertise for your product or provides services and need to increase customer or having website or blog, social media is the best option to spread your ideas to a vast audience.

Social media nowadays plays an important role in our routine life.

People spend more and more their free time on social media such as Facebook, twitter, WhatsApp, Instagram, LinkedIn etc.

Providing options to share your post on social media is the first thing you should do to drive better traffic on your blog or website.

As the Facebook is at the top in terms of people’s engagement, we had already discussed how to add Facebook like and share button and how to add twitter button to your blog post in the previous posts. If you haven’t read it yet, you better read it first before proceeding to this article.

Similar to Facebook and Twitter, LinkedIn is also one of the largest social platform to share your thoughts and ideas globally so having a LinkedIn share button to your blog post will surely help to reach your content at a large extent.

In this post, we will learn how to add LinkedIn button to your website or blog post without bothering much about the code.

There are hundreds of plugins are available such as Social Share Button, AddToAny, WP Share, Easy Social Share etc. that allows to add almost all social sharing buttons at once without writing a single line of code.

Well, providing a LinkedIn button isn’t a big deal. Anyone can do it with just following a simple couple of steps. So without bothering much about theory, let’s see it in action.

LinkedIn Share Button

To add the Official Linkedin Share button to your blog post simply open up a theme file of your choice (single.php etc) and add the following code within the Post Loop:

Vertical Count

Vertical count will display the counter on top of the button as displayed in the preview image.

<script type="text/javascript" src="http://platform.linkedin.com/in.js"></script>
<script type="in/share" data-url="<?php the_permalink(); ?>" data-counter="top"></script>

Horizontal Count

Horizontal count will display the counter to the right on the button as displayed in the preview image.

<script type="text/javascript "src="http://platform.linkedin.com/in.js"></script>
<script type="in/share" data-url="<?php the_permalink(); ?>" data-counter="right"></script>

No Count

No count will not display the counter to the button as displayed in the preview image.

<script type="text/javascript" src="http://platform.linkedin.com/in.js"></script>
<script type="in/share" data-url="<?php the_permalink(); ?>"></script>

Because this was announced recently, there are no plugins for this yet but surely will be available in future.

If you like this post, don’t forget to share and hit like button!

Today social media serves as the biggest platform as a means of communication globally.

It helps to share your idea, thoughts across the globe.

If you own a business and want to advertise for your product or provides services and need to increase customer or having website or blog, social media is the best option to spread your ideas to a vast audience.

Social media nowadays plays an important role in our routine life.

People spend more and more their free time on social media such as Facebook, twitter, WhatsApp, Instagram, LinkedIn etc.

Providing options to share your post on social media is the first thing you should do to drive better traffic on your blog or website.

As the Facebook is at the top in terms of people’s engagement, we had already discussed how to add Facebook like and share button to your blog post in the previous post. If you haven’t read it yet, you better read it first before proceeding to this article.

Similar to Facebook, Twitter is also one of the largest social platform to share your thoughts and ideas globally so having a tweet button to your blog post will surely help to reach your content at a large extent.

In this post, we will learn how to add tweet button to your website or blog post without bothering much about the code.

There are hundreds of plugins are available such as Social Share Button, AddToAny, WP Share, Easy Social Share etc. that allows to add almost all social sharing buttons at once without writing a single line of code.

Well, providing a Tweet button isn’t a big deal. Anyone can do it with just following a simple couple of steps. So without bothering much about theory, let’s see it in action.

Visit twitter’s web official web page https://publish.twitter.com/. It would look similar to the one as shown below. It describes the complete process step by step.

Enter your website URL for which you wish to tweet.
Next you will be presented with the following option. Select twitter buttons from it.

You can customize the Tweet button by clicking on set customization options where you can select pre-populated text for the message, and confirm which Twitter accounts you’d like to suggest to users. The main account you specify will become an @mention in the Tweet. (By default, we’ll use the username of whichever account you’re currently logged into in the button.)
Copy and paste the code into the HTML of your website wherever you wish the button to appear.
Congratulation! You’re done!

If you like this post, don’t forget to tweet and hit like button!

A we know that one of the responsibilities of the Operating System is to use all hardware resources efficiently.

To achieve this, a fast access time and disk bandwidth is required.
The access time is affected by two major components: seek time and rotation latency.

Seek Time

The seek time is the time taken for the disk arm to move the disk head to the cylinder containing the desired sector.

Rotation Latency

Rotational latency is the additional time waiting for the disk to rotate the desired sector to the disk head.

Band Width

Bandwidth is the total no of bytes transferred directly between the first request for service and the completion of last transfer.

Both access time and Bandwidth can be improved by scheduling the servicing of disk input output request in an efficient manner.

A system call to the Operating System is made whenever any process requires performing input output to or from the disk.

This request specifies the following information.

What type of operation is it? Input or output?
What is the disk address to transfer?
What the memory address for transfer is?
What no. of bytes is to be transfer?

The request can be serviced immediately if desired disk drive and controller are available

If the drive or controller is busy, any new request for service will be placed on the waiting queue for that drive.

For a multi-programming system the disk queue may have often several pending request.

Thus when one request is completed the Operating System selected the next service which is pending.
There are various algorithms available for the disk scheduling.

Some commonly used disk scheduling algorithms are as follow:

First Come First Serve (FCFS)
Shortest Seek Time First (SSTF)
Scan Algorithm
C-Scan Algorithm
Look and C-Look Algorithm

We will try to understand each of these algorithms in our up coming posts. so stay tuned.

Today social media serves as the biggest platform as a means of communication globally.

It helps to share your idea, thoughts across the globe.

If you own a business and want to advertise for your product or provides services and need to increase customer or having website or blog, social media is the best option to spread your ideas to a vast audience.

Social media nowadays plays an important role in our routine life.

People spend more and more their free time on social media such as Facebook, twitter, WhatsApp, Instagram, LinkedIn etc.

Providing options to share your post on social media is the first thing you should do to drive better traffic on your blog or website.

As the Facebook is at the top in terms of people’s engagement, in this post I will teach you how to add Facebook like and share button to your blog post.

Well, providing a Facebook like or share button isn’t a big deal. Anyone can do it with just following a simple couple of steps. So without bothering much about theory, let’s see it in action.

Visit Facebook official page. It would look similar to the one as shown below. It describes the complete process step by step.

Choose URL or Page

Pick the URL of a website or Facebook Page you want to use with the like button.

Code Configuration

Paste the URL to the code configurator and adjust settings like the width of your like button. If you don’t’ want to customize the width of the button then default will be fine.

Select layout for your like button from the layout drop down. Possible layout options are standard, box_count, button_count, and button. Default is standard. You will be shown with the preview of the selected layout.

Select button size as per your requirement. Possible button sizes are small and large.

Uncheck “Show Friends’ Faces” if you don’t wish to show faces.
Uncheck “Include Share Button” if you just want like button. By default it is checked means it shows both Facebook like and share button. You can play around with the options.

Finally click the Get Code button to generate your like button code. It will show you the generated code similar to the one given below.

Copy & Paste HTML snippet

Copy and paste the snippet into the HTML of the destination website.

The first code snipped should be included after the opening of <body> in your header file.

Paste the second code snipped to the page or post wherever you wish to appear your Facebook like button. For example normally it is in single.php file in case of WordPress.

Finally refresh your page and congratulation you have done the job!

If you like this post, don’t forget hit like button!

There are many directory structure schemes to implement the behavior of directories. Some common implementation schemes are as follow:

Single Level Directory Structure

This is the simplest directory structure to implement.

All files are contained in the same directory.

Limitation of single level directory structure is that when number of files increase or when the system has more than one user, it becomes unmanageable.

Since all files are in this same directory, the name must be unique.

File names are generally selected to reflect the contents of the file, they are often limited in length.

Dos allows only 11 character file name and UNIX allows 255 characters.

Two Level Directory Structure

A single level directory has file names collision between different users.

One solution is to create a separate directory for each user.

In the 2 level directory structure each user has its own user file directory (UFD).

Each UFD has similar structure but list only the files of a single user.

When a user job start or user logs in, the system master file directory (MFD) is searched.

When a user refers to any specific file only his won UFD is searched.
Thus different users will have files with the same name.

Although the 2 level directory structure solves the name collision problem but it has still disadvantages.

This structure effectively isolated one user from another.

This isolation is an advantage when the users are completely independent.

But it is a disadvantage when the users want to cooperate on some task and want to excess each other’s files.

If excess is to be permitted, one user must have the ability to name a file in another user directory.

To name a particular file uniquely in a 2 level directory, we must give both the user name and file name.

A 2 level directory can be thought of as a tree and as an inverted tree the height of it is 2.

The root of the tree is MFD.

Its direct descendants is one of the UFD’s.

The descendants of the UFD are the files and files are leaves of the trees.

Thus a user name and a file name define a path name.
Every file in this system has path name.

To name a uniquely user must known the path name of the file desired.

System files are part of the system loader, assembler, compilers, utility, routines, libraries and so on. They are generally defined as files.

When the appropriate commands are given to the o/s then these files are read and execute.

Tree Structure Directory

It allows user to create their own sub-directories and to organize their files accordingly.

This is the natural and most common directory structure organization.

It has no any fixed height, it can be extended.
The Ms Dos system is structured as a tree.
The tree has a root directory.

Every file in this system has unique path name.

A path name is the path from the root through all the sub-directories to a specified file.

A directory contains a set of files or sub directories.
A directory is simply another file but it is treated in a special way.
All directories have the same internal format.

One bit in each directory defines the entry as a file (0) or as a sub directory (1).
Special system calls are used to create and delete directories.

There are two ways to specify a file path:

Absolute Path

In this path we can reach to a specified file from the main or root directory.
In this case current directory is not involved; file path is specified starting from the root directory.

Relative Path

The user working in any directory that directory is called current directory.
To reach to a specified file we have to search from the current directory.

Hello everyone, after discussing file system in our previous post, we are moving on to our next topic in operating system which is I/O Hardware.

Computer uses different types of devices to perform operations.

These devices can be categories as storage devices (disks, tapes), transmission devices(network card, modem), and human-interface devices (keyboard, mouse)

A device communicates with computer system by sending signals over a cable or through air.

The device communicates with computer via connection point or port.
Devices may be connected through bus.

A bus is a set of wires which is used to transfer data from and to the I/O devices and memory.

When device A has a cable that plugs into device B, and device B is plugged into device C, and device is connected into a computer port then such arrangement is called a Daisy chain.

Buses vary in their signaling methods, speed, throughput, and connection methods.

Examples of widely used common buses are PCI and SCSI bus.

The PCI bus (Peripheral Component Interconnect) connects processor-memory subsystem to the fast devices.

The expansion bus connects slow devices such as keyboard and serial and USB port

The disks are connected together on SCSI bus plugged into a SCSI controller.

A controller is a collection of electronics that can operate a port, a bus or a device.

A serial-port controller is a simple device controller. It is a single chip that controls the signals on the wires of a serial port.

A SCSI bus controller is a complex so normally it is implemented as a separate circuit board.

It contains a processor, microcode, and private memory to process SCSI protocol messages.

Some devices have their own in-built controllers.( such as disk drive that contains circuit board at one side)

It has microcode and a processor to perform many task such as bad-sector mapping, buffering, and catching.

Controller has one or more registers for data and control signals.

The processor communicates with the controller by reading and writing bit value in these registers

The graphics controller has a large memory-area to store screen contents.

The process sends output to the screen by writing into this memory-area.

An I/O port normally contains four registers:

Data-in register

read by the host to get input.

Data-out registers

Which is written by the host to send output.

Status register

It indicates status such as current command has completed, a byte is available to be read from the data-in register or a device error is generated.

Control register

It can be written by the host to start a command or to change the mode of a device. For example enabling parity checking, speed supported by the port.