Exam 70-483 topic 2 question 124 discussion

Actual exam question from Microsoft's 70-483

Question #: 124
Topic #: 2

You are developing an application that includes methods named ConvertAmount and TransferFunds.
You need to ensure that the precision and range of the value in the amount variable is not lost when the TransferFunds() method is called.
Which code segment should you use?

A. Option A
B. Option B
C. Option C
D. Option D

Show Suggested Answer

Suggested Answer: A 🗳️
The double keyword signifies a simple type that stores 64-bit floating-point values.
The float keyword signifies a simple type that stores 32-bit floating-point values.
Reference: double (C# Reference)

by supersunny at July 25, 2019, 7:39 a.m.

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supersunny

Highly Voted 5 years, 10 months ago

A is good for the requirement.

upvoted 11 times

ptarasov

5 years, 4 months ago

Why not B?

upvoted 4 times

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rhysabray

Highly Voted 5 years, 3 months ago

It seems both A and B are correct, but if I had to pick then I choose B. A - Converts float(4 bytes) to double(8 bytes) and keeps the double B - Converts float(4 bytes) to decimal(12 bytes) and keeps the decimal Because both are being converted to something more precise and do not undergo further conversions then both are suitable. However, decimal needs 12 bytes of memory and millions of stored values in this form would certainly be larger than storing the same number of doubles. Despite this, Decimals do not employ the same ability to lose or round digits through conversion unlike their binary counterparts and as the question explicitly asks to ensure that "precision and range is not lost". Within finance, use decimals, people don't like losing money through rounding errors.. so B! Anywhere else, A would be the best - less memory and usually tiny rounding errors wont matter.

upvoted 7 times

Ragou

5 years ago

the requirement are to keep precision and range of the float. Only the double is suitable for both: https://stackoverflow.com/questions/618535/difference-between-decimal-float-and-double-in-net float: ±1.5 x 10^-45 to ±3.4 x 10^38 (~7 significant figures) double: ±5.0 x 10^-324 to ±1.7 x 10^308 (15-16 significant figures) decimal: ±1.0 x 10^-28 to ±7.9 x 10^28 (28-29 significant figures)

upvoted 6 times

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