In this presentation, I covered the following topics: 1. Introduction to Ruby 2. Variables 3. Datatypes 4. Decision-making Statements 5. Looping Statements 6. Simple I/O 7. Array and its methods 8. Hashes and its methods 9. Class and Object 10. Iterators

2.  Ruby is a pure object-oriented programming
language.
 It was created by Yukihiro Matsumoto of Japan.
 Ruby is a server-side scripting language, which
can be embedded into HTML.

3.  All ruby files will have extension .rb. To run ruby
programs use ruby file_name.rb.
 For single-line comment you can use the hash character
(#) at the beginning of a line. For multi-line
=begin/=end.
 Ruby interprets semicolons and newline characters as
the ending of a statement.
 Following a << you can specify a string or an identifier
to terminate the string literal.

5.  BEGIN – Declares code to be called before the
program is run.
BEGIN
{
code
}
 END – Declares code to be called at the end of the
program.
END
{
code
}

6.  Local variables: Local variables are the
variables that are defined in a method.
 Instance variables: Instance variables are
available across methods for any particular
instance or object. That means that instance
variables change from object to object. Instance
variables are preceded by the at sign (@)
followed by the variable name.

7.  Class variables: A class variable belongs to the
class and is a characteristic of a class. They are
preceded by the sign @@ and are followed by
the variable name.
 Global variables: A global variable can
available across classes. The global variables are
always preceded by $ sign.

8.  Numbers
 Strings
 Symbols
 Hashes
 Arrays
 Booleans

9. if...else Statement
if conditional [then]
code...
[else
code...]
end
else...if Statement
if conditional [then]
code...
[elsif conditional [then]
code...]...
[else
code...]
end

10. if modifier
code if condition
unless modifier
code unless condition
unless Statement
unless conditional [then]
code
[else
code ]
end

11. case Statement
case expression
[when expression [, expression ...] [then]
code ]...
[else
code ]
end

12. while Statement
while conditional [do]
code
end
until Statement
until conditional [do]
code
end

13. while Modifier
code while condition
or
begin
code
end while condition
until Modifier
code until condition
or
begin
code
end until condition

14. for Statement
for variable [, variable ...] in expression [do]
code
end
(expression).each do |variable[, variable...]|
code
end

15. gets
 gets is used to read from the user and store in
string form.
 to_i is used convert string to integer and to_f is
used to convert string to float.
puts
 puts is used to display a string on the output
screen.
print
 print is also used to display a string or a variable
value on the output screen.

16.  Ruby arrays are ordered collections of any object.
Creating Arrays
 There are many ways to create or initialize an
array.
 var = Array.new or var = Array.new(size)
 var = Array.[](value1,value2,….) or
var = Array[value1,value2,….] or
var = [val1,val2,…]

17.  array.at(index)
 array.clear
 arrray.delete(obj)
 array.delete_at(index)
 array.empty?
 array.index(obj)
 array.insert(index,obj)
 array.join(sep)
 array.length
 array.pop
 array.push(objs)
 arr.reverse!

18.  A hash is a collection of key-value pairs.
Creating Hashes:
 var_name = Hash.new()
 var_name = Hash.new(obj)
 var_name = Hash[key1=>value1,key2=>value2…]
 var_name = {key1=>value1,key2=>value2…}

19.  hash.clear
 hash.delete(key)
 hash.empty?
 hash.fetch(key[,default])
 hash.has_key?(key)
 hash.has_value?(value)
 hash.invert
 hash.keys
 hash.length
 hash.merge(other_hash) or hash.merge!(other_hash)
 hash.values

20.  Ruby methods are used to bundle one or more repeatable
statements into a single unit.
Syntax:
def method_name [( [arg [= default]]...[, * arg [, &expr ]])]
#method_body
end
return
 return statement is used to return one or more values from a
method
Syntax:
return [expr[, expr...]]

21.  A class is a collection of data members and member functions.
Syntax:
class class_name
@@class_variables
def initialize()
@instance_variables
end
def function_name
statements
end
end
Creating Object:
obj = class_name.new

22.  Iterators are nothing but methods supported by
collections. Objects that store a group of data members
are called collections.
Syntax:
collection.each do |variable|
code
end
 The collect iterator returns all the elements of a collection.
Syntax:
collection2 = collection1.collect