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Ch 2 . Number Systems and Codes. 2.2 Octal and Hexadecimal Numbers. 10 ~ 15 : Alphabet . 2.3 General Positional-Number-System Conversions. p digit to the left of the point and n digits to the right of the point. Ex) A number D of the form has the value . p. n.
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Ch 2. Number Systems and Codes 2.2 Octal and Hexadecimal Numbers 10 ~ 15 : Alphabet
2.3 General Positional-Number-System Conversions • p digit to the left of the point and n digits to the right of the point Ex) A number D of the form has the value p n
Number conversion example (decimal to hexadecimal, octal) 16 8 567 1234 70 77 16 8 2 7 4 8 13 6 8 1 0
Number conversion example (decimal to octal) 0.78 8 8 8 8 6.24 1.92 7.36
: Carry in : Burrow in : Input data 1 : Input data 2 : Carry out : Sum : Burrow out : Difference 1 0 1 0 1 - + - + 1 0 1 1 1 1 1 1 1 0 0 1 1 1 Burrow in Carry in Carry out Carry out Burrow out Burrow out
2.4 Addition and Subtraction of Nondecimal Numbers
2.5 Representation of Negative Numbers • Signed-Magnitude System • Magnitude and Symbol ( ‘+’, ‘-’ ) • Applied to binary number by using ‘sign bit’ • Ex) Sign bit • Complement System • Negates a number by taking its complement • More difficult than changing the sign bit • Can be added or subtracted directly
: :
Conversion example Number : Easy to complement
2.7 One’s-Complement Addition and Subtraction One’s complement End-around carry +6 (0110) + -3 (1100) 10010 1 0011
Binary to Gray Code Gray Code to Binary (0) 1 1 0 (0) 1 0 1 1 3 2 1 2 1 1 0 1 0 1 3 If different, ‘1’ else (same) ‘0’ If different, ‘1’ else (same) ‘0’
Hamming Distance • Distance between two vertices, the number of difference bits in each position • EX) D(010, 111) = 2
If minimum distance = 2C+1, • up to C-bits can be corrected • If 2C+D+1, then C-bits can be corrected, • and d bits can be detected • 4= 2C+D+1, • C=1, D=1 • 1 bit can be corrected • D=3, 3 bit errors can be detected
111 110 101 100 011 010 001
LSB is 1 if all 7 bits are odd LSB is 0 if all 7 bits are even
k = # of parity bits m = # of info bits , m=4,3,2,1 , m=11,10,9,…,2,1
NRZ : Non-Return to Zero NRZI : Non-Return to Zero Invert on 1s BPRZ : Bipolar Return to Zero