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Chapter 3 Coding System (3.3 Number Reresentation in Computer System…
Chapter 3 Coding System
3.1 Binary, Denary & Hexadecimal
3.5 Character Coding Systems
Character coding system represents character
can be manipulated efficiently by computer
Chinese Character
Coding System
Big5 Code
mainly used
represent traditional
Chinese character
double bytes
Guo Biao (GB) Code
standard code for simplified Chinese character
1-4 bytes
Unicode
represent all existing language
cover about 100,000 characters
1-4 bytes (120,000 characters)
American Standard Code for Information Interchange (ASCII)
originally 7 bits
now 8 bits
stored up 2^7 (128) character
e.g. alphanumeric character
& graphics symbols
3.3 Number Reresentation in Computer System
Bit = 1 Binary Digit
e.g. 8 bit represents 256 distinct values
n bit represents 2^n distinct values
1 byte = 8 bits
1 KB = 1024 Bytes
1 MB = 1024 KB
1 GB= 1024 MB
1 TB= 1024 GB
1 PB = 1024 TB
Word length = natural unit of processing data= n
Two's Complement
2 = 0010
1 = 0001
0 = 0000
-1 = 1111
-2 = 1110
3.2 Number System Conversion
Binary
to Denary
0000 = 0
0011 = 3
to Hexadecimal
0011 0000 1101 = 30D
1101 = D
Denary
to Binary
0 = 0000
3 = 0011
to Hexadecimal
11433 = 2CA9
3.4 Addition and Subtraction of Different Number Representations
overflow error
the result cannot be represented by fixed number of digits
addition of two's complement numbers is the same as that of unsigned binary integers
-occurs when two numbers of the same sign are added and the result has the opposite sign
