Input and Output
Computers have many senses -- keyboard, mouse, network card, digital camera, etc. Collectively, these are called INPUT.
Computers can also express themselves in many ways -- text, graphics, sound, network, printers, etc. Collectively, these are called OUTPUT.
Input and Output together are called I/O.
putsmeans "print a line to the terminal"
getsmeans "read a line from the terminal"
getsreads all the characters from the keyboard and puts them into a new string, until you press RETURN
LAB: Hello, friend!
hello.rbin your text editor
Change it to contain the following code:
puts "What is your name?" name = gets puts "Hello, " + name + "!"
Save the file and switch back to the terminal
Run the program using
Type in your name and press the Return key (also called Enter)
What happens? Is this what you expected?
Uh-oh! We've got trouble... what is that exclamation point doing way down there?
The first thing to do is DON'T PANIC!
You are totally going to figure this out.
And even if you don't, you haven't actually broken anything.
In fact, it's really hard to break a computer, so just stay calm.
- In through the nose...
- Out through the mouth...
- In through the nose...
Let's fix this
- Have you figured out what the problem is?
- If not, I'll tell you on the next slide.
- Take a second and try to figure it out first. I'll wait.
The newline character
- Here's a fun fact:
- In addition to letters, numbers, and punctuation, computers also store other keys inside strings
- Among these CONTROL CHARACTERS is the one that represents the RETURN KEY
- This character's name is NEWLINE
- Every time you use
gets, Ruby reads all the characters, including the newline!
- Fortunately, there's an easy fix
- If you send the message
stripto a string, it will remove all SPACES and NEWLINES from both ends
LAB: fixing Hello, Friend
Change the program to look like this:
puts "What is your name?" name = gets.strip puts "Hello, " + name + "!"
Run it and make sure it works OK
- What happens if you type your name in all lowercase?
- Make the program capitalize your name for you even if you forget.
LAB: Crazy Name
- Now go crazy and make it do all sorts of silly things to your name!
LAB: Full Name
- Write a program named
name.rbthat asks two things:
- Your first name
- Your last name
- Then it says hello to the user by her full name.
- Run the program by typing
ruby name.rbon the command line.
You just wrote a program!
You are now officially a coder. HIGH FIVE!
Lab: Name Length
name.rbso it also prints the number of characters in the user's name.
What is your first name? Alex What is your last name? Chaffee Hello, Alex Chaffee! Your name is 11 characters long.