Gain insights into Ruby development with 78 tasks tailored for beginners and experienced coders. Explore object-oriented concepts, debug programs, and advance your freelance coding career.

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This self-study course written as a book is your first step towards making money by coding and programming from home, and having fun doing it. You will understand how the Ruby language works, and establish a foundation for being a successful freelance developer. This course gives you not only technical detail, but presents knowledge in a friendly format, understandable by all ages, providing a thorough explanation of modern concepts for absolute beginners.

In this course you will find 78 easy to follow tasks, so even people without any programming skill can solve them. Beginners will learn how to create, debug, and understand programs in Ruby. Those who are already familiar with the language will rediscover object-oriented concepts, memory organization, find career advice, and save the planet from a nuclear apocalypse.

Ready to dive into one of the most influential and demanding third generation programming languages? Let's tune in!

The Handbook for Ruby Developers

# Hello, I'm your REPL

In the case of the `1 + 1` program from the previous chapter, the interpreter performs two actions: read (R) and evaluate (E). We used no “print” action (`puts` in our case), so no result was displayed on the screen. In other words, to see the results we need to perform these three actions:

* Read (R\)
* Evaluate (E)
* Print (P\)

It would also be nice if we could avoid running the `ruby` command from the terminal every time, so that we can execute programs in a constant loop (L). It turns out that this functionality is already there! The REPL acronym stands for **Read Evaluate Print Loop.**


It’s very similar to the Ruby interpreter, but differs in that it accepts the “Enter” key as the end of our program. Instead of exiting on Ctrl+D, signifying end of input, it just starts reading the input again. REPL is a well-known acronym, which is not tied to the Ruby language infrastructure. Other languages have their own REPLs too. Ruby’s REPL is called `irb`. We can type this command from our shell:

```
$ irb
2.5.1 :001 >
``` 

The numbers at the beginning of the line are just indicators of the Ruby version we’re using, such as `(2.5.1)`. The same output is produced when the ruby `-v` command is run. `001` indicates the first string. In the future, we’ll see how we can type multiline mini-programs to REPL. Since the REPL acronym already contains the word “print” in it, we don’t need to type `puts`. Regardless of what we do, the result will be printed on our screen.


The principle of least surprise says that to exit REPL, we should type `exit`. Let’s do that now to see if it works.


Authors rarely use the default `irb` as a REPL. There is a better alternative called [Pry](http://pry.github.io/). It has the same functionality, but offers more flexibility and room for configuration.




Learn to execute Ruby programs in the Ruby interactive shell called `irb`, and learn how to run a program from a file.

Before We Begin

First Steps

Fundamentals of Ruby

Conditional Statements

Operators and Methods

Arrays

Hash

Fun with Object Oriented Programming

Debugging in Ruby

Ruby Version Manager

Testing Ruby Programs

Wrap Up!

Appendix

REPL

Hello, I’m your REPL