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Ruby Basics

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Variables

5:15 with Jay McGavren

Variables can hold numbers, text, a calendar date, or any other piece of data that can be stored in your computer's memory.

  • Variables in a programming language are like variables in algebra, but they can hold other things besides numbers. They can hold text, or a calendar date, or any other piece of data that can be stored in your computer's memory.
  • When you assign a value to a variable, you're giving that value a name that you can refer to it by.
  • You assign a value to a variable with a single equals sign: = 
number = 4
greeting = "hello"
  • We can then use that variable anywhere we might use the original piece of data.
puts number # 4
puts greeting # "hello"
puts number + 2 # 6
puts 12 - number # 8
  • If we change the value the variable holds, the remainder of the program will use that new value instead of the old one.
number = 6
greeting = "hi"

puts number # 6
puts greeting # "hi"
puts number + 2 # 8
puts 12 - number # 6
  • We can even replace the value a variable holds in the middle of a program.
  • Valid variable names - same as method names.
    • All lower case
    • Numbers are legal but rarely used
    • Snake case - separate words with underscores.
word = "hi"
multiple_words = "hi there"

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    What if we wanted to be able to specify how long it should wait for? 0:00
    puts and print both take text that they want displayed. 0:02
    sleep takes a number of seconds to sleep for, but how are they doing that? 0:05
    Before we can answer that we need to explain variables. 0:10
    Variables aren't a complex concept but they're fundamental to programming. 0:13
    You probably remember working with variables in your Algebra class. 0:18
    They were often denoted with with an X or a Y and 0:21
    were used to hold a variety of possible values. 0:24
    That is, variables are names for values that can vary. 0:27

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