CPT4

This is my CPT4 AQA 2009 Revision Cards

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• Created by: Henry
• Created on: 27-01-09 20:00

Number Bases and Representations

Hexdecimal Goes From 1-9 as Denary then From Then To A-F From 10-15 in Denery

To Convert Denery To Hexidecimal

• First Convert to Binary
• Then Chunk into Groups of four
• Convert those Binary chunks to Denery
• Then Use the above numbering System to work out hexidecimal

To Convert Hexidecimal to Deneray Follow the Process in reverse

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This is how negitive numbers are represented in Two's a Complment

11111101 = -3

11111110 = -2

11111111 = -1

00000000 = 0

00000001 = 1

Conveting a Negitive number to Binary

• Find the binary equivlent of the positive decimal number
• Change all the 0's to 1's and the 1's to 0's
• Add 1 To the result

The alternitive is to

• Find the binary equivlent of the positive decimal number
• Starting from right, leave all the didgits alone up to and includin the first 1
• Change all the other didgits from 0 to 1 or from 1 to 0

The eaisiest way to convert back is write out the binary headings above the 0's and ones as you do normally but leave the left most bit negitive and add up and work out the number eg
-128 64 32 16 8 4 2 1 1 0 0 0 1 1 1 0
-128 + 8 4 2 -------- -114
Binary Subtraction ......

1 of 2

2 of 2