# CPT4 Revision

CPT4 revision notes for AQA AS Computing.

- Created by: Adam Hagan
- Created on: 16-10-07 07:51

First 180 words of the document:

Version 3

CPT4: Binary and Binary Coded Decimal Revisited

Binary Representation:

The binary representation of 45 is:

128 64 32 16 8 4 2 1

0 0 1 0 1 1 0 1

Representation of a denary number to binary is done altogether by adding up to

create 45.

BCD (Binary Coded Decimal) Representation

The BCD representation of 45 is:

8 4 2 1 8 4 2 1

0 1 0 0 0 1 0 1

Representation in BCD is done by finding the binary code for each the `4' and

the `5'.

CPT4: Hex Numbers

The primary purpose of hex is to represent the binary code in a format easier for

humans to read and acts as a shorthand of binary.

Denary Value Hex Value

0 0

1 1

2 2

3 3

4 4

5 5

6 6

7 7

8 8

9 9

10 A

11 B

12 C

13 D

14 E

15 F

16 1

Method:

What is the Hex value of 45?

1. Find how many times 16 goes into 45 (45 div 16 = 2)

2. So the hex value for this is `2'

3. Find the value of the remainder (45 (16*2) = 13)

4. So the hex value for 13 is `D'

5. The full Hex value is 2 D.

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