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CSE 2353 Spring 2006. Number Systems. Number Systems. Normal everyday math is in base 10 (decimal numbers) Why? Computers function in base 2 (binary numbers) Why? When interpreting computer data, humans often use base 8 (octal) or base 16 (hexadecimal) Why?. Number Systems.
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CSE 2353 Spring 2006 Number Systems SMU - Dunham
Number Systems • Normal everyday math is in base 10 (decimal numbers) • Why? • Computers function in base 2 (binary numbers) • Why? • When interpreting computer data, humans often use base 8 (octal) or base 16 (hexadecimal) • Why? SMU - Dunham
Number Systems • Decimal numbers: 0,1,2,…,9 • Binary numbers: 0,1(Bit) SMU - Dunham
Number Systems • Octal numbers: 0,1,…,7 Group binary by threes • Hexadecimal numbers: 0,1,2,…,9,A,B,C,D,E,F Group binary by fours SMU - Dunham
Exercises (EX #4) • Write the first 10 (in decimal) numbers in each number system. • Convert 101010 (binary) to decimal and octal and hexadecimal. • Convert 3920 (decimal) to binary (Algorithm p20) and octal (p22) and hexadecimal (p25). • Convert 756 (octal) to binary and decimal and hexadecimal • Convert D5E (hexadecimal) to binary and decimal and octal SMU - Dunham
How is Data Represented? • What does 01010111 mean? • If an instruction, then the opcode indicates what it is • If not an instruction then must be interpreted differently: • Integer - Based on number system used by machine and instruction • Real - Based on how real numbers are stored for this machine and instruction • Character - Based on encoding scheme (ASCII, EBCDIC) SMU - Dunham
Basic Integer Number Systems • Pp 68-74 • Unsigned: 0 to • Sign Magnitude: to • High order bit indicates sign (0-positive; 1-negative) • Low order (n-1) bits indicates “number” • One’s Complement: • Positive same as sign magnitude • Negative number obtained by inverting all bits • Same range as sign magnitude SMU - Dunham
Basic Integer Number Systems • Two’s Complement • Range: to • Positive same as sign magnitude • Leftmost bit is sign (0-positive, 1-negative) • Negative number: Invert bits and add 1 • 8088/8086 • Excess • Same range as two’s complement • Leftmost bit is sign (0-negative, 1-positive) SMU - Dunham
Why Different Number System? • Range supported • Ease of operations • Number of zeros SMU - Dunham