1. Hexadecimal and ASCII
Lesson Objective: Understand the purpose of ASCII and how to use it.
Lesson Outcome: Convert between Hexadecimal and ASCII
Convert Hexadecimal to Denary
Key words: 8 bit byte, decimal, hexadecimal

2. Each place is called a BIT (Binary digIT)
Bits and Bytes
128 64 32 16 8 4 2 1
8 Bits make one BYTE
Each place is called a BIT (Binary digIT)

3. Question
What is a BIT?

4. Question
How many bits are there in this byte?
Answer = 8

5. Question
How many bytes are there in a kilobyte?
Answer = 1024

6. Converting from binary to decimal8 4 2 1 =3 =9
=10 =7 =5
=15

7. Converting between decimal and binary
128 64 32 16 8 4 2 1
= = 71
128 64 32 16 8 4 2 1
= = 18

8. Converting between decimal and binary
128 64 32 16 8 4 2 1
= = 35
= = 50
= = 99

9. Binary and Hex digits ...
= 0
= 8
= 1
= 9
= A
= 2
= 3
= B
= 4
= C
= 5
= D
= 6
= E
= F
= 7

10. Binary to hex conversion (For lazy people)
= 115
Written as:
7316 Or
73Hex 7 3
Assign a number to each of the nibbles ...

11. A = 01000001 How is data stored? Book Vs Computer
A book stores data with ink and paper
A computer stores data as electronic 0’s and 1’s A =
Remember from a previous lesson … 8 bit byes, kilobytes ..etc.

12. Converting between decimal and binary
10000s
1000s
100s
10s 1s
05565
128 64 32 16 8 4 2 1
= = 65

13. What are the following binary numbers in decimal?
What are the following binary numbers in Hexadecimal? 8
128 4 64 2 32 1 16 8 8 4 4 2 2 1 1
= 67
= 43Hex
= 78
= 4EHex

14. How are letters, numbers and symbols held in the computer?
NO!
A = 1, B = 2, C = 3 … etc?
All characters are held in a universally recognised coded called:
ASCII
Say Ass-Key
A = 65, B = 66, C =67 … a = 97, b=98

15. ASCII ... A
American S
Standard C
Code for I
Information I
Interchange

16. Worksheets!

17. Coverting Hex to Denary:16 1
42Hex = 4 2
= 4 x x 1 =
= 66 16 1
2AHex = 2 A
= 2 x x 1 =
= 42

18. Coverting Hex to Denary:16 1
C5Hex = C 5
= 12 x x 1 =
= 197 16 1
EAHex = E A
= 14 x x 1 =
= 234