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7/24/2019 Coding System in Computer
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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 +
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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.
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&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.
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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!