Learning Plan 3 : Math and Operators

Making variables and putting data into them.

Numbers:

• Here's what the number 7 looks like in the computer:

00000000000000000000000000000111

• That's 32 bits in a row, which is maybe a little overwhelming. So, we break up the bits into groups of 8 that we call bytes. (You've probably heard that term, like in a 250GB hard drive. That's 250 billion bytes!)

00000000 00000000 00000000 00000111

• For the sake of discussion, we'll not worry about the first 3 bytes since they are all zeros. We'll just look at the last byte.

00000111

• Now we'll blow it up and look at what it means. The computer only understands base 2 arithmetic. The rightmost bit is the ones position, the next one to the left is the twos positions, next is the fours, etc.
  

  

• Here's what 10 looks like:

00001010

• Here's 255:

11111111

• And here's 682 but we had to add back the next byte:

00000010 10101010

• What about letters? Here's what the letter A is in the computer:

01000001

• Huh? That looks like a number! Yep, that's what everything is in the computer. That's also the number 65.
• How does the computer know that it's an A and not 65?
• Because we tell it that it's an A. That's what Assignment means.

Assignment is setting a variable to a value and telling the computer the value's type.

• In JavaScript we do this by simply assigning a value to a variable. JavaScript figures out what type based on how you write the value:
  • Numbers: 45, 123.99
  • Strings: "this is a string", "Here's another", "12.99"
  • A number is declared by not using quotes.
  • A string is declared with the quotes, even if the value is a number.
• There are several ways to do assignment in JavaScript. The simplest is the Simple Assignment Operator.

  

• Simple Assignment when declaring the variable:

• Simple Assignment after the variable has been declared. This can happen anywhere in your code after the declaration.

• Simple Assignment with Math

• Simple Assignment by replacing the value of a variable:

• Simple Assignment to a new type. JavaScript is what is sometimes called a "loosely typed" language. This means that variables can be any type and you can change their type. Many other languages, like Java and C#, are "strongly typed" languages. Their variables have to be declared a type and you can't change the type.

• You can also assign the value of a variable with the results of a function. This is very common and will look very normal quickly.

• Simple Assignment can be done to a variable "in-place", from itself to itself.