What does the “M” stand for in decimal value assignment?

Question

MSDN says:

\"Without the suffix m, the number is treated as a double, thus generating a compiler error.\"

What does the \"M\" in:

decimal curren         


        

Answer 1

M makes the number a decimal representation in code.

To answer the second part of your question, yes they are different.

decimal current = (decimal)10.99

is the same as

double tmp = 10.99;
decimal current = (decimal)tmp;

Now for numbers larger than sigma it should not be a problem but if you meant decimal you should specify decimal.

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Update:

Wow, i was wrong. I went to go check the IL to prove my point and the compiler optimized it away.

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Update 2:

I was right after all!, you still need to be careful. Compare the output of these two functions.

class Program
{
    static void Main(string[] args)
    {
        Console.WriteLine(Test1());
        Console.WriteLine(Test2());
        Console.ReadLine();
    }

    static decimal Test1()
    {
        return 10.999999999999999999999M;
    }
    static decimal Test2()
    {
        return (decimal)10.999999999999999999999;
    }
}

The first returns 10.999999999999999999999 but the seccond returns 11

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Just as a side note, double will get you 15 decimal digits of precision but decimal will get you 96 bits of precision with a scaling factor from 0 to 28. So you can represent any number in the range ((-2⁹⁶ to 2⁹⁶) / 10^{(0 to 28)})

Answer 2

Well... I think "D" would be confused with double, so... they chose "M"? Maybe for "Money"? Seems a bit silly... but I couldn't find anything definitive.

Answer 3

Description

decimal current = 10.99M; 

Tells the compiler you want a decimal number.

decimal current = (decimal)10.99

Tells the compiler you want to cast your double 10.99 to a decimal.

Some say it stands for money. M because you must use decimals in financial applications. You must use decimals because they are more accurate than floating point numbers (double).

The decimal suffix is M/m since D/d was already taken by double. Although it has been suggested that M stands for money, Peter Golde recalls that M was chosen simply as the next best letter in decimal.

The decimal has more significant figures than the double, therefore it can be more precise- it also takes up slightly more memory. Other than certian math or physics-related algorithms, the double or float should do fine.

For example

• If you do ANYNUMBER / 0.5d you will not get the half of ANYNUMBER.

• If you do ANYNUMBER / 0.5m you will get everytime the half of ANYNUMBER.

• Use decimal for money

• Use double for exchange rates

More Information

• Decimal vs. Double - difference?
• What Every Programmer Should Know About Floating-Point Arithmetic