Download pdf - Coding System in Computer

7/24/2019 Coding System in Computer

http://slidepdf.com/reader/full/coding-system-in-computer 1/4

Coding Systems in Computer

How Computers Store Numbers

Computer systems are constructed of digital electronics. That meansthat their electronic circuits can exist in only one of two states: ON

or OFF. These patterns of "on" and "off" stored inside the computerare used to encode numbers using the binary number system.

The representation of numbers in computer can be done in

• Binary ( Numbers in base 2)

• Octal (Numbers in base )

• Decimal (Numbers in base ! )

• Hexadecimal. (Numbers in base !# )

Decimal System

$ecimal notation is the writing of numbers in the base%ten numeralsystem& which uses 'arious symbols (called digits) for no more than

ten distinct 'alues (& !& 2& & & *& #& +& and ,) to represent anynumbers& no matter how large.

The 'alues of each position correspond to powers of the base of thenumber system. -o for our decimal number system& which uses base!& the place 'alues correspond to powers of !:

... ! ! ! !

...! !2 !! !

Binary Code

/undreds Tens 0nits 1esult

! # ! x ! # x ! 3 !#

x ! 3

+ x ! x ! + 3 +



The binary number system is a method of storing ordinary numbers

such as 2 or #* as patterns of !4s and 4s. 5ecause of their digitalnature& a computer4s electronics can easily manipulate numbersstored in binary by treating ! as "on" and as "off." Computers ha'ecircuits that can add& subtract& multiply& di'ide& and do many other

things to numbers stored in binary.

The Octal Number System (Base-!

The octal number system uses 678/T 'alues to represent numbers.The 'alues are& & !& 2& & & *& # 9 +with "ero ha'ing the least 'alue and se#en ha'ing the greatest

'alue. Columns are used in the same way as in the decimal system&in that the left most column is used to represent the greatest 'alue.

ctal was used extensi'ely in early mainframe computer systems&but has become less popular in fa'our of binary and hexadecimaltoday.

The Hexadecimal Number System (5ase%!#)The hexadecimal number system uses -7;T66N 'alues to representnumbers. The 'alues are&

& !& 2& & & *& #& +& & ,& $% B% C% D% & and Fwith ' ha'ing the least 'alue and F ha'ing the greatest 'alue./exadecimal is often used to represent 'alues (numbers and memoryaddresses) in computer systems.

$SC $lphanumeric Code

<-C77 stands for American S tandard C ode for I nformation I nterchange. 7t is a code for representing 6nglish characters asnumbers& with each letter assigned a number from to !2+. Thestandard <-C77 character set uses =ust + bits for each character.

The BCD Number System5inary Coded $ecimal (5C$) is a system in which each integer of adecimal number is represented by a %bit binary number.

http://www.webopedia.com/TERM/A/bit.html

http://www.webopedia.com/TERM/A/bit.html



&BCDC

65C$7C (6xtended 5inary Coded $ecimal 7nterchange Code ) is abinary code for alphabetic and numeric characters that 75>de'eloped for its larger operating systems. 7t is an bit code and canpro'ide 2*# different characters. 7t is used on 75> mainframes andon other large computers.

)&)O*+ ,NTSBit

< binary digit is called a bit. 0sually expressed as and ! the twonumbers of the binary numbering system. < bit is the smallest unit of information a computer can use.

1eading a series of bits is 'ery difficult and to ma?e this processeasier they are often displayed in groups of bits ! !!!! !!

!

< group of bits is called a NBB&. 7t contains four digits. 6.g.!!& !& e.t.c

Byte

< group of bits are in a byte. @ith bits ( binary digits )& thereexists /01 possible denary combinations.< byte can represent any alphabetical letter& single digit& or a single

characterAsymbol& such as B.arge numbers of bytes can be expressed by 2ilobyte% me3abyte%

3i3abyte and terabyte. &.3.

The word DCO)4,T&* E has byte or characters. 7t contains # Bits

and !# nibbles.



Kilobyte

The 'alue of a ?ilobyte is !2 5yte. @or?ed out as /5' bytes.Normally Filo refers to ! but in computing ?ilobyte is !2.

Megabyte

i?ewise& !2 Filobyte (Fb) is referred to as a ">egabyte". Normallya >ega refers to a million. 7n computing ! >ega byte is !&&*+#bytes. @or?ed out as //' bytes or !2 6 !2.

Gigabyte

The 'alue of a gigabyte is !2 >b. That is% /7' bytes

n summary%

Bits 8 5 Byte

5'/9 Bytes 8 5 :ilobyte (:b!

5'/9 :b 8 5 )e3abyte ()b!

5'/9 )b 8 5 ;i3abyte (;B!

5'/9 ;B 8 5 Terabyte (Tb!