Chapter 2 : Computer System (Part 3)

2.3 Information Coding Schemes

Data Representation

How computers represent  data?

-Data and instructions can be represented electronically by using bits consists of 1 (on) and 0(off) and byte consists of 8 bits grouped together as a unit to store a single character up to 256 individual characters.

-Data representation refers to the form in which data is stored, prosessed, and transmitted in computers.

-Daigital data is text, numbers, graphics, sound, and video that has been converted into bit patterns of 0s and 1s called binary numbers.

Representing Numbers

-Computers represent all numeric data (numbers) with the binary system.

Number	Binary Representation
0	00000000
1	00000001
2	00000011
3	00000100

Representing Character Set

How can a computer represents non-numeric characters (character data)?

-Information Coding Schemes

3 Coding Scheme/System

-ASCII (American Standard Code for Information Interchange)

-EBCDIC (Extended Binary Coded Decimal Interchange Code)

-Unicode

ASCII

-ASCII (pronounced “ask-ee”) is the most widely used coding scheme to represent a set of characters.

-Uses 8 bits to represent  a character.

-Represent 256 characters (2⁸ =256)

-Primarily used on minicomputers, personal computers and servers.

-ASCII coding schemes uses 8 bits to represent a character, meaning that storing data in ASCII takes up less memory.

-The 256 characters that are represented by ASCII coding system are only sufficient for English and Westerns European languages but is not large enough for Asian and other languages that use siftillferent alphabets.

-Example : PAY $8!

P	A	Y	SPACE	$	8	!
01010000	01000001	01011001	00100000	00100100	00111000	00100001

EBCDIC

-EBCDIC is widely considered to be an outdated coding system, but it still used in some equipment, mainly on IBM mainframe and IBM midrange computer operating systems in order to allow for continued use of software written many years ago that expects an EBCDIC communication environment

-Uses 8 bits to represent a character

-Represent 256 character (2⁸ = 256)

-Primarily used on IBM mainframes, midrange systems and high-end servers.

-EBCDIC coding scheme uses 8 bits to represent a character, meaning that storing data in EBCDIC takes up less memory

-The 256 characters that are represented by EBCDIC coding scheme are only sufficient for English and Westerns Europeans languages but is not large enough for Asian and other languages that uses different alphabets.

-Example : PAY $8!

P	A	Y	SPACE	$	8	!
01010000	01000001	01011001	00100000	00100100	00111000	00100001

UNICODE

-Unicode is a 16 coding scheme that has the capacity of represent all the world’s current languages as well as classic and historical languages, in 65,536 characters.

-Uses 16 bits to represent a character.

-Represent 65,536 characters (2¹⁶ = 65,536).

-Implemested in several operating systems including Windows, Mac OS, and Linux.

-Unicodecan represent 65,536 characters (2¹⁶= 65,536) capable of representing almost all the world’s current languages, classical and historical languages and symbols.

-Unicode coding scheme uses 16 bits to represent a character, meaning that storing data in Unicode takes up more memory.

-Example: PAY $8!

P	A	Y	SPACE	$	8	!
0000	0000	0000	0000	0000	0000	0000
0000	0000	0000	0000	0000	0000	0000
0101	0100	1010	0010	0010	0011	0010
0000	0001	1001	0000	0100	1000	0001

CHARACTERISTICS OF THE CODING SCHEME

CHARACTERISTIC	ASCII	EBCDIC	UNICODE
NUMBER OF BITS	Uses 8 bits to represent a character	Uses 8 bits to represent a character	Uses 16 bits to represent a character
NUMBER OF CHARACTERS	Represents 256 characters (28 = 256 )	Represent 256 characters (28 = 256)	Represent 256 characters (216 = 65,536)
USAGE	Primarily used in minicomputers, personal computers and server	Primarily used on IBM mainframe, midrange systems and high-end servers	Implemented in several OS (Windows, Mac OS, X, Linux)

(Continue : Part 4)