1. **Literals** are notations for representing some fixed values in code. Python has various types of literals – for example, a literal can be a number (numeric literals, e.g., `123`

), or a string (string literals, e.g., “I am a literal.”).

2. The **binary system** is a system of numbers that employs *2* as the base. Therefore, a binary number is made up of 0s and 1s only, e.g., `1010`

is *10* in decimal.

Octal and hexadecimal numeration systems, similarly, employ *8* and *16* as their bases respectively. The hexadecimal system uses the decimal numbers and six extra letters.

3. **Integers** (or simply **int**s) are one of the numerical types supported by Python. They are numbers written without a fractional component, e.g., `256`

, or `-1`

(negative integers).

4. **Floating-point** numbers (or simply **float**s) are another one of the numerical types supported by Python. They are numbers that contain (or are able to contain) a fractional component, e.g., `1.27`

.

5. To encode an apostrophe or a quote inside a string you can either use the escape character, e.g., `'I\'m happy.'`

, or open and close the string using an opposite set of symbols to the ones you wish to encode, e.g., `"I'm happy."`

to encode an apostrophe, and `'He said "Python", not "typhoon"'`

to encode a (double) quote.

6. **Boolean values** are the two constant objects `True`

and `False`

used to represent truth values (in numeric contexts `1`

is `True`

, while `0`

is `False`

.

**EXTRA**

There is one more, special literal that is used in Python: the `None`

literal. This literal is a so-called `NoneType`

object, and it is used to represent **the absence of a value**. We’ll tell you more about it soon.

**Exercise 1**

What types of literals are the following two examples?

`"Hello ", "007"`

They’re both strings/string literals.

**Exercise 2**

What types of literals are the following four examples?

`"1.5", 2.0, 528, False`

The first is a string, the second is a numerical literal (a float), the third is a numerical literal (an integer), and the fourth is a boolean literal.

**Exercise 3**

What is the decimal value of the following binary number?

`1011`

It’s `11`

, because (2**0) + (2**1) + (2**3) = 11