Data Types


  • basic unit in programming.

Data Type


  • Numbers
  • Strings
  • Boolean values (True or False)


  • Describe — numbers are used to express value: what is the frequency of a sound wave? We can express that in a number, such as 800hz.
  • Calculate — numbers are used in calculations: what’s the distance between the earth and mars?
  • Count — numbers are used to keep track: how many times did the car go around the track?


  • represent other forms of data other than numbers
  • Strings are any sequence of characters (letters, spaces, numbers, or symbols). While almost anything can be a string, they are typically used to represent text or speech. Similar to how we represent speech in writing, we surround strings with single ('...') or double quotes ("...").

Uses of Strings

  • To display data that uses text or symbols, like printing our name to the screen.
  • To add or remove text. Since strings are a linear sequence of characters, we can break strings into even smaller strings, or combine strings to make longer ones.
  • To modify characters. For example, we could capitalize the first letter of every word in a string if wanted to turn it into a title.
  • To let the computer communicate with us in a “human-readable” way, like displaying the rules of an online game.


  • only have two values: true and false
  •  Logic is important to computer science because it is an early attempt at translating the human capacity for reason to computers.
  • act as binary opposites

The term boolean comes from the inventor of a specific form of logic, George Boole.

Uses of Boolean

  • To determine validity. For example, we want to know whether a meme is viral. If it’s been viewed more than 50 million times in less than a week, we’d say that it’s true that it went viral.
  • To make decisions. For example, if I get an email, the program checks that the email is new and it displays at the top of my inbox.


  • Making calculations using arithmetic operators.
  • Comparing information using comparison operators.
  • Creating logical expressions using logical (aka Boolean) operators.
  • are symbols that represent different ways of modifying, comparing, and evaluating information.

Arithmetic Operators

used to make calculations.

  • Addition adds an amount to a number: 2 + 3 = 5
  • Subtraction takes away an amount from a number: 10 - 3 = 7
  • Multiplication takes a number and repeats it a specified number of times: 5 * 2 = 10
  • Division takes a number and divides it by another number: 15 / 3 = 5

Comparison Operators

determine the relationship between two values, which results in a boolean.

  • Less than < — value to the left is less than the value to the right: 2 < 6
  • Greater than > — value to the left is more than the value to the right: 14 > 5
  • Equals == — value to the left is equal to the value to the right: 3 == 3

If we have an unknown quantity. 

strawberry_weight = ?
is (strawberry_weight == .5lb)? => true

If we need to compare two known values.

bananas = 5
oranges = 3

is (oranges > bananas)? => false

Boolean Expressions

  • Expressions that evaluate to boolean values are known, true or false

Logical Operators

determine the logical state of multiple boolean values or expressions, which results in another boolean.

  • also known as boolean operators, evaluate multiple boolean expressions.
  • it looks at several relationships by connecting them with logical operators and then determining the logic/validity of the overall expression.
  • AND — both expressions evaluate to true, so the final result is true:
    • ((4 > 1) AND (2 < 7)) is the same as (TRUE AND TRUE). Evaluates to true.
  • OR — one of the expressions evaluates to true, so the final result is true:
    • ((8 > 6) OR (3 > 6)) is the same as (TRUE OR FALSE). Evaluates to true.
  • NOT — an expression, no matter its logical value, evaluates to the opposite:
    • NOT (1 < 3) evaluates to NOT (TRUE). Evaluates to false.

The larger the sample size and the more diverse your dataset is, the more confident you’ll be in your results.

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