understand the difference between numbers and digits.


# 12 is a number, but '12' is a string of two digits.

puts  12  +  12
puts '12' + '12'
puts '12  +  12'

# 24
# 1212
# 12  +  12

1.	Storing Data in Variables
2.	Define a variable to hold an integer
3.	give a value a name by assigning it to a variable
4.	variables can point to any kind of object
5.	Variables allow you to write and use programs that work upon varying data.
6.	variables can also be assigned the results of an expression
7.	Doing a calculation
8.	create a variable and compare it with a number.
9.	Exchanging Values Without Using Temporary Variables
10.	Exchange three value with using new variables
11.	Assign values to more than one variable in one statement
12.	Assign constant array value to three variables
13.	Exchange value with an extra variable
14.	Math calculation
15.	x, y = 1, 2 # Same as x = 1; y = 2
16.	Swap the value of two variables
17.	Array elements automatically assigned to variables
18.	Variables in a Class
19.	Prefix and variable type
20.	Interpolation with two variables
21.	Everything Is an Object
22.	Objects Might Have Their Own Methods

understand the difference between numbers and digits. : Variables « Language Basics « Ruby