What is a computer?

• A calculating machine
  • desktop
  • laptop
  • cell phone
  • smart phone

The Universal Machine

• A computer can do anything
  • (at least on the inside)
• This can be intimidating!
• But the basic rules are simple

The Terminal

• the TERMINAL is a window into which you can talk directly to your computer

In The Beginning Was The Command Line

• the TERMINAL is a window into which you can talk directly to your computer

• aka console or command line or command prompt or shell or prompt

  • contrast CLI (Command Line Interface) to GUI (Graphical User Interface)

• "In The Beginning Was The Command Line" is an essay by Neil Stephenson describing the history of computers in an enjoyable and clever way

{Ruby} irb - the Interactive Ruby Browser

Exercise: Calculator

• open a terminal
• type irb
• press the Return key (also called Enter)
• see the > prompt
• type 1 + 1
• press the return key again
• see the 2

• yay, a $1000 calculator!

• Bonus: what other math can you do?

• From now on, whenever you see text in the code font, try typing it into irb and see what happens!

node - the Interactive JavaScript Executor

Exercise: Calculator

• open a terminal
• type node
• press the Return key (also called Enter)
• see the > prompt
• type 1 + 1
• press the return key again
• see the 2

• yay, a $1000 calculator!

• Bonus: what other math can you do?

• From now on, whenever you see text in the code font, try typing it into irb and see what happens!

Computer Anatomy

• hardware
  • CPU
  • Memory
  • Storage
  • Input/Output Devices (monitor, keyboard, etc.)
• software
  • Operating System
  • Drivers
  • Programs
• wetware
  • that's you!

Computer Anatomy: Hardware

• CPU ("the brain")
• Memory
• Input/Output
  • keyboard, mouse, touch screen, monitor

The basic architecture of computers has not changed since the invention of the Von Neumann Architecture in the 1940s.

Computer Anatomy: Software

• Operating System
• Libraries
• Drivers
• Applications
• Languages

Every piece of software on your computer is a PROGRAM.

A Program Is Like A Recipe

• a recipe is a collection of ingredients and instructions

• a program is a collection of data and code

When you are writing code, you are not baking cookies, you are writing a recipe for how to make cookies.

• coding is more like America's Test Kitchen than like Top Chef -- you may run many test batches, but the goal is not cookies, but a recipe so someone else can make cookies later

(recipe from popcornpottery.com)

Languages

• every program is written in a LANGUAGE
  • like Java or Python or C or Fortran
  • even HTML and CSS and SQL are languages
  • every computer language has a silly name
• different languages are useful in different areas, but there is a lot of overlap
• today we will learn the RUBY programming language

Errors Are Awesome

• Don't be afraid of errors
• Your computer is trying to help you fix your program
  • It's just really bad at communicating

If your code is a two-year-old child, then an error is a temper tantrum.

• It's not all gibberish
• Try to read it -- really try! -- and pull out the pearls from the pig slop

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