1. Binary and Hard Disk PEOPLE Program
Good afternoon everyone, welcome to the Binary section of PEOPLE program. 2 day event, today talk,

2. How do Computers Store Numbers
Computers are constructed of digital electronics => two states: “on” “off”
Binary number system consists of 0 and 1 only
On-off patterns are used to encode numbers using binary number system
Most computer electronics
Voltage levels
CD-ROM
Microscopic dark spots on disk surface
Hard disk
Magnetism
Computer memory
Electric charges on capacitors
As you may have learnt before
Two states which can represent 0 and 1 resepectively

3. Binary numbers are great!
Simple to work with
No big addition and multiplication tables to learn
Just do same things over and over very fast
Just use two values of voltage, magnetism or other signal
Hardware easier to design and more resistant
For example, for decimal system, 45 rules; for binary, 4 rules
Better robustness

4. Hard Drive
Hard disks are used in all desktop computers, servers, super computers etc. They are also VCR type devices or video recorders that use hard drives instead of tape
They store changing digital information in a relatively permanent form. They give computers the ability to remember things when the power goes out.
Different from RAM, where info will be lost after turn off power.

5. How Does Binary Work? Decimal number system Expanded notation: … 1000
10 digits (0 to 9)
Add a second column worth 10 times the value of the first column
Expanded notation:
3 x x = 365
1 x x x = 1032 …
1000
100 10 1
Or 10 to the first, or 10 to the second

6. Binary Number System Only contains two digits: 0,1
Add a second column worth 2 times the value of the first column
To convert a number from binary to decimal, use expanded notation: =
1x32 + 0x16 + 1x8 + 1x4 + 0x2 + 1x1
= 45 1 … 32 16 8 4 2 1

7. Binary  Decimal Any desired amount can be represented using 1 and 0.
Examples
1 == 0001
3 == 0011
6 == 0110
1  a power of 2
0  zero
Examples
0001  2^0 = 1
0010  2^1 = 2
0100  2^2 = 4
1000  2^3 = 8
0101 = = 5
1010 = = 10
0111 = = 7

8. Larger Numbers Numbers from 1 to 15
0000 = = = = = = = = = = = = = = = = 15
Bigger whole numbers  more bits more places in binary number
= = 133
This is 8 bits == 1 byte

9. Larger Numbers 10000101 = 128 + 0 + 0 + 0 + 0 + 4 + 1 = 133
This is 8 bits == 1 byte
Kilobyte = 1024 bytes (1024 = 2^10)
Megabyte = 1024 kilobytes ~ a million bytes
Gigabyte = 1024 megabytes

10. Typical Sizes Typical Hard disks are 100 – 500 gigabyte
1 byte == 1 character
 hard disk might hold 100 billion characters ~ 20 billion words of raw text
Real numbers, fractions, very large numbers
 floating point arithmetic

11. Binary Addition Decimal System Binary System
Sum >= 10  add 1 to the column on the left
Binary System
Sum >= 2  add 1 to the column on the left
Example: = 11
= 100
110101

12. Binary Addition Second Way Convert the numbers to decimal
Add the decimal numbers
Convert the sum to binary

13. ASCII Table ASCII: American Standard Code for Information Interchange
Alphanumeric characters are represented with 8 bits
A  65 ==
Write 3 letters in ASCII Table
How to represent letters in computers?
Pass ASCII Table to students