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Slide 5.6: Signed integers Slide 5.8: Signed integers (cont.) Home         Print version

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Signed Integers (Cont.)

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Two’s Complement of Hexadecimal
An easy way to reverse the bits of a hexadecimal digit is to subtract the digit from 15.

Starting value:   (15,268)10 = (3BA4)16		3	B	A	4
Step 1: Reverse the digits
Step 2: Add 1 to the value from Step 1	+	0	0	0	1
Sum
2’s complement notation of (-15,268)10 is	( )16

Converting Signed Binary to Decimal

• If the highest bit is a 0, convert the unsigned binary integer to decimal.
• If the highest bit is a 1, it is stored in two’s complement notation.

Starting value: (11010100)2		1	1	0	1	0	1	0	0
Step 1: Reverse the bits
Step 2: Add 1 to the value from Step 1	+	0	0	0	0	0	0	0	1
Step 3: Form the two’s complement
Step 4: Convert to decimal	negative ( )2 = ( )10

Converting Signed Decimal to Binary

• Convert the absolute value of the decimal integer to binary.
• If the original decimal integer was negative, form the two’s complement of the binary number.

Starting value: (-38)10	(-38)10
Step 1: Convert the absolute value to binary
Step 2: Reverse the bits
Step 3: Add 1 to the value from Step 2	+	0	0	0	0	0	0	0	1
Step 4: Form the two’s complement
2’s complement notation of (-38)10 is	( )2

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I’d tell you if you were going around the bend (crazy) .