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RDBMSRDBMS stands for Relational Database Management System. It stores data in form of entity as tables. It provides multiple layers on information security. Each table may or may not have a primary key which identifies a record uniquely in a table and a foreign key which indentifies the relationship between two tables. RDBMS uses SQL language to query databases. Examples of popular RDBMS are oracle, sql server, mysql etc.MongoDBMongoDB is a NoSQL database. It is open source. It is a document oriented database and it uses BSON which is binary version of JSON. BSON is a document storage format. MongoDB ... Read More
ReactJSReact or ReactJS was originally developed by Facebook and it acts on view layer for web and mobile based application. It integrates well with Node js environment. Following are key features of React.Scalability - react is highly adaptable and scalable library.Rich in features - Provides extensions to existing javascript and typescript languages.Reusablity - react components are highly reusable.Vue.jsVue.js is javascript based MVC framework and is very helpful in creating responsive UI.Following are key features of Vue.js.Scalability - Vue.js is highly adaptable and scalable library.Rich in features - Provides extensions to existing html components.Reusablity - Vue.js components are highly reusable and ... Read More
JPEG and PNG both are a type of image format to store images. JPEG uses lossy compression algorithm and image may lost some of its data whereas PNG uses lossless compression algorithm and no image data loss is present in PNG format.Following are the important differences between JPEG and PNG.Sr. No.KeyJPEGPNG1Stands forJPEG stands for Joint Photographic Experts Group.PNG stands for Portable Network Graphics.2Compression Algorithm typeJPEG uses lossy compression algorithm.PNG uses lossless compression algorithm.3Image QualityJPEG image may lose some image data causing quality loss.PNG image is of high quality.4Image sizeJPEG image is generally smaller than PNG image of same image.PNG image ... Read More
You can also extract a "slice" from an array - that is, you can select more than one item from an array in order to produce another array.Example Live Demo#!/usr/bin/perl @days = qw/Mon Tue Wed Thu Fri Sat Sun/; @weekdays = @days[3, 4, 5]; print "@weekdays";OutputThis will produce the following result −Thu Fri SatThe specification for a slice must have a list of valid indices, either positive or negative, each separated by a comma. For speed, you can also use the .. range operator −Example Live Demo#!/usr/bin/perl @days = qw/Mon Tue Wed Thu Fri Sat Sun/; @weekdays = @days[3..5]; print "@weekdays";OutputThis will ... Read More
Perl provides a number of useful functions to add and remove elements in an array. You may have a question what is a function? So far you have used the print function to print various values. Similarly, there are various other functions or sometimes called subroutines, which can be used for various other functionalities.Sr.No.Types & Description1push @ARRAY, LISTPushes the values of the list onto the end of the array.2pop @ARRAYPops off and returns the last value of the array.3shift @ARRAYShifts the first value of the array off and returns it, shortening the array by 1 and moving everything down.4unshift @ARRAY, ... Read More
The size of an array in Perl can be determined using the scalar context on the array - the returned value will be the number of elements in the array −@array = (1, 2, 3); print "Size: ", scalar @array, "";The value returned will always be the physical size of the array, not the number of valid elements. You can demonstrate this, and the difference between scalar @array and $#array, using this fragment is as follows −Example Live Demo#!/usr/bin/perl @array = (1, 2, 3); $array[50] = 4; $size = @array; $max_index = $#array; print "Size: $size"; print "Max Index: $max_index";OutputThis ... Read More
Perl offers a shortcut for sequential numbers and letters. Rather than typing out each element when counting to 100 for example, we can do something like as follows −Example Live Demo#!/usr/bin/perl @var_10 = (1..10); @var_20 = (10..20); @var_abc = (a..z); print "@var_10"; # Prints number from 1 to 10 print "@var_20"; # Prints number from 10 to 20 print "@var_abc"; # Prints number from a to zHere double dot (..) is called range operator. This will produce the following result −1 2 3 4 5 6 7 8 9 10 10 11 12 13 14 15 16 17 18 19 20 a b c d e f g h i j k l m n o p q r s t u v w x y z
When accessing individual elements from an array in Perl, you must prefix the variable with a dollar sign ($) and then append the element index within the square brackets after the name of the variable. For example −Example Live Demo#!/usr/bin/perl @days = qw/Mon Tue Wed Thu Fri Sat Sun/; print "$days[0]"; print "$days[1]"; print "$days[2]"; print "$days[6]"; print "$days[-1]"; print "$days[-7]";OutputThis will produce the following result −Mon Tue Wed Sun Sun MonArray indices start from zero, so to access the first element you need to give 0 as indices. You can also give a negative index, in which case you select ... Read More
Perl Array variables are prefixed with the @ sign and are populated using either parentheses or the qw operator. For example −@array = (1, 2, 'Hello'); @array = qw/This is an array/;The second line uses the qw// operator, which returns a list of strings, separating the delimited string by white space. In this example, this leads to a four-element array; the first element is 'this' and last (fourth) is 'array'. This means that you can use different lines as follows −@days = qw/Monday Tuesday ... Sunday/;You can also populate an array by assigning each value individually as follows −$array[0] = 'Monday'; ... $array[6] = 'Sunday';
A Perl array is a variable that stores an ordered list of scalar values. Array variables are preceded by an "at" (@) sign. To refer to a single element of an array, you will use the dollar sign ($) with the variable name followed by the index of the element in square brackets.ExampleHere is a simple example of using the array variables − Live Demo#!/usr/bin/perl @ages = (25, 30, 40); @names = ("John Paul", "Lisa", "Kumar"); print "\$ages[0] = $ages[0]"; print "\$ages[1] = $ages[1]"; print "\$ages[2] = $ages[2]"; print "\$names[0] = $names[0]"; print "\$names[1] = $names[1]"; print "\$names[2] = $names[2]";Here we ... Read More