What is C?

C programming is one of thousands of computer programming languages that allow users to create instructions for a computer to follow. While C has a slightly more cryptic style than some other programming languages, it's fairly easy to learn and allows you to read and write code for many different platforms. Because it's so efficient and gives the user a lot of control, C is very popular with programmers.
The C programming language has been around since the early '70s, when it was developed by Ken Thompson and Dennis Ritchie at Bell Laboratories. They saw the need for a more user-friendly programming language, and after several attempts at new languages, C was eventually finalized and released. Throughout the '80s, the developers created various standards for the language. As computers became more complex, programmers were able to use C to build their own compilers and programming languages. The C programming language has led to the development of both Java and C++, which are popular today and both simplified programming even further.
C is a compiled language, which means that once your C program is written, you'll need to run it through a C compiler to convert the program to an executable form. The computer can then run the C program. The C compiler is vital to creating a C program, because without it, your program will remain in human-readable form as opposed to machine-readable form [source: King]. Programmers can either purchase a commercial compiler or download a free C compiler online.
One of the things that programmers like about C is that it enables them to scale down programs so they can run on very little memory. This has become especially important in recent years, when so many people are using small-scale computers like smartphones and tablets.

What is Ruby?

Ruby is unique among object-oriented scripting languages. In a sense, it's a purist's language for those who love object-oriented languages. Everything, without exception, is automatically an object, whereas in other programming languages this isn't true.
What is an object? Well, in a sense you can think of it in terms of building a car. If you have a blueprint for it, then an object is what's built from that blueprint. It contains all the attributes that the object holds (i.e. make, model, color) and the actions it can perform. But, even as a pure object-oriented language, Ruby doesn't sacrifice any usability or flexibility by leaving out features that aren't expressly related to object-oriented programming.
Ruby's architect Yukihiro Matsumoto (known simply as "Matz" on the web) designed the language to be simple enough for beginning programmers to use while also powerful enough for experienced programmers to have all the tools they'd need. It sounds contradictory, but this dichotomy is owed to Ruby's pure object-oriented design and Matz's careful selection of features from other languages such as Perl, Smalltalk and Lisp.
There are libraries for building all types of applications with Ruby: XML parsers, GUI bindings, networking protocols, game libraries and more. Ruby programmers also have access to the powerful RubyGems program. Comparable to Perl's CPAN, RubyGems makes it easy to import other programmers' libraries into your own programs.

What is Perl?

Perl is a programming language which can be used for a large variety of tasks. A typical simple use of Perl would be for extracting information from a text file and printing out a report or for converting a text file into another form. But Perl provides a large number of tools for quite complicated problems, including systems programming.
Programs written in Perl are called Perl scripts, whereas the term the perl program refers to the system program named perl for executing Perl scripts. (What, confused already?)
If you have used shell scripts or awk or sed or similar (Unix) utilities for various purposes, you will find that you can normally use Perl for those and many other purposes, and the code tends to be more compact. And if you haven't used such utilities but have started thinking you might have need for them, then perhaps what you really need to learn is Perl instead of all kinds of futilities.
Perl is implemented as an interpreted (not compiled) language. Thus, the execution of a Perl script tends to use more CPU time than a corresponding C program, for instance. On the other hand, computers tend to get faster and faster, and writing something in Perl instead of C tends to save your time.

What is Java?

Java is a high-level object-oriented programming language developed by the Sun Microsystems. Though it is associated with the World Wide Web but it is older than the origin of Web. It was only developed keeping in mind the consumer electronics and communication equipments. It came into existence as a part of web application, web services and a platform independent programming language in the 1990s.
Earlier, C++ was widely used to write object oriented programming languages, however, it was not a platform independent and needed to be recompiled for each different CPUs. A team of Sun Microsystems including Patrick Naughton, Mike Sheridan in the guidance of James Goslings decided to develop an advanced programming language for the betterment of consumer electronic devices. They wanted to make it new software based on the power of networks that can run on different application areas, such as computers and electronic devices. In the year 1991 they make platform independent software and named it Oak. But later due to some patent conflicts, it was renamed as Java and in 1995 the Java 1.0 was officially released to the world.
Java is influenced by C, C++, Smalltalk and borrowed some advanced features from some other languages. The company promoted this software product with a slogan named “Write Once Run Anywhere” that means it can develop and run on any device equipped with Java Virtual Machine (JVM). This language is applicable in all kinds of operating systems including Linux, Windows, Solaris, and HP-UX etc.