# Do Now (in Classroom)

The letter `A` is represented by `65` in ASCII, the protocol used by most computers for text encoding.

American Standard Code for Information Interchange, a set of digital codes representing letters, numerals, and other symbols, widely used as a standard format in the transfer of text between computers.

Deep inside your computer, that `65` is sent in binary. What is `65` in binary?

## π― Learning Targets

I can use number bases, including binary, decimal, and hexadecimal, to represent and investigate digital data.

I can explain why hexadecimal is used to represent digital data.

## Review decimal & binary

Letβs write 15:

Decimal:
In decimal, we have 10 symbols: `0, 1, 2, 3, 4, 5, 6, 7, 8, 9`.

15 in decimal:

1000 100 10 1
Β  Β  1 5

Binary
In binary, we have 2 symbols: `0, 1`

15 in binary:

8 4 2 1
1 1 1 1

Binary numbers start to get very long, very quickly.

## Hexawhatnow?

Hexadecimal In hexadecimal, we have 16 symbols: `0, 1, 2, 3, 4, 5, 6, 7, 8, 9, a, b ,c, d, e, f`

Wait, what?

15 in hexadecimal is `f`.

4096 256 16 1
Β  Β  Β  f

## Notice!

• How many `bits` does it take to write 15 in decimal, binary, and hexadecimal?
• Hex looks just like decimalβ¦until we try to write 16:

4096 256 16 1
Β  Β  1 0

Where have we seen hex before?

#E32173

Thatβs my favorite pink, Razzmatazz. Colors can be represented by mixing red, green, and blue. How much RGB is Razzmatazz?

Itβs 227 red, 33 g, and 115 blue. How do I know that?

Razzmatazz R G B
Hex E3 21 73
Decimal 227 33 115