December 1998
LD201: LOGIC DESIGN

QUESTION 2

Total Marks: 20 Marks

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SUGGESTED SOLUTIONS
for Question 2

 

(a) In the context of floating point numbers, what is meant by normalisation? Why is this process necessary?

 

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(b) Explain carefully why 2's complement format is used in preference to the older formats of sign-modulus and 1's complement.

 

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(c) 2's complement numbers can be multiplied by powers of 2 using the operation of arithmetic shift left. Explain the two circumstances in which this operation can cause an overflow to occur.

 

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(d) Can the corresponding arithmetic shift right operation ever cause an overflow? Explain your answer.

 

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(e) (i) Show how the hexadecimal number -1.AA16 can be written in normalised floating point format, with a 10-bit mantissa and a 4-bit exponent.

 

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(ii) Show how the octal number 1.2628 can be written in the same normalised floating point format, with a 10-bit mantissa and a 4-bit exponent.

 

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(iii) Working in the same floating point format, perform floating point addition to calculate the sum

-1.AA16  +  1.2628 = ...

Convert your answer to decimal format

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