CS485 Syllabus
Information encoding

• Communicating information

• Fact:

 In a communication, a sender conveys some information to one or more receivers

• \$64,000 question:

 What excatly is information ????

• What is information ?

• For English speaking people, this is information:

 ``` The car is red ```

• For English speaking people, the following may not be information:

 ``` El carro es rojo ```

Why ?

 It's information if you can decode it (and use it).. Otherwise, it's jibberish.

• Case in point:

This is for most people jibberish (except if you can read Demotic script)

• Representing information: Information encoding

• Fact:

 Information is always represented through an "encoding" scheme

• Encoding scheme:

 Encoding scheme = a set of rules on how to interprete a set of symbols The set of symbols is called a code

• Code:

 Code = a representation scheme that is agreed by a group of entities

• Example:

• The English alphabet is an example of an encoding method !!!

Example:

 ``` A (this symbol is meaningless to a person in the Amazon jungle !) ```

• Representing information in a computer

• Information stored inside a computer must be represented using:

 Binary numbers !!! (or "binary signals") (That's because the memory of a computer can only store binary digits)

• Example of encoding methods that uses Binary numbers:

• The 2's complement encoding method (which you learned in CS255):

 ``` Code Value represented by code ============================================= 11111111 -1 00000000 0 00000001 1 .... ```

• ASCII code:

 ``` Code Character represented by code =============================================== 01100001 'a' 01100010 'b' .... ```

Alpha-numerical information inside the computer is represented using the ASCII code

• Other kinds of codes

• Recall: Code

 A code is a prescribed (mutually agreed) representation

There are many different codes used in the world... (and more are being developed....)

• A not so obvious binary code: Morse code

Fact:

 The information represented by Morse code is often "store" in sound/electrical waves !!! Example: tapping "S O S" - 3 short taps, 3 long taps, 3 short taps