What is E in floating point?

Asked 21/5, 2012 at 14:18 Answered 21/5, 2012 at 14:21

Solved c#.net floating-point scientific-notation

What is E+3? What exactly happens here? Can we use this approach in other data types or can we only use it in floating point numbers?

static void Main(string[] args)
{
    double w = 1.7E+3;
    Console.WriteLine(w);
}

Output: 1700

Ossieossietzky answered 21/5, 2012 at 14:18 Comment(5)

The answers you will get for the various languages will be similar, but not identical. Please choose one programming language and limit your question to it. – Barbital 21/5, 2012 at 14:19

E+3 == 10^3 == 10*10*10 == 1000. Thus, 1.7 * 1000 = 1700. It's called "engineering notation" afaik – Soapberry 21/5, 2012 at 14:20

I wonder why would anybody prefer 1.7E+3 compared to just 1700. – Edict 21/5, 2012 at 14:24

@Rob: I don't know about asp, but for all the other languages he's chosen, the answer is in fact identical. – Cordellcorder 21/5, 2012 at 14:29

@Edict - Because for much larger or smaller numbers it is more compact, e.g., 1.7E+30 is easier than typing or reading the 29 zeros in 1700000000000000000000000000000. (And if you know you'll be dealing with a range of large numbers it is often easier to stick to the one notation style. I wouldn't use E notation if I knew all the numbers I needed were only up to four or five digits.) – Favourite 22/5, 2012 at 6:4

E notation

Most calculators and many computer programs present very large and very small results in scientific notation. Because superscripted exponents like 10⁷ cannot always be conveniently displayed, the letter E or e is often used to represent times ten raised to the power of (which would be written as "x 10^b") and is followed by the value of the exponent. Note that in this usage the character e is not related to the mathematical constant e or the exponential function e^x (a confusion that is less likely with capital E); and though it stands for exponent, the notation is usually referred to as (scientific) E notation or (scientific) e notation, rather than (scientific) exponential notation (though the latter also occurs). The use of this notation is not encouraged by publications.

As for your second question:

can we use this approach in other data type or we can only use it in floating points?

See the C# spec:

Real literals [the type of numeric literals that are allowed an E in them] are used to write values of types float, double, and decimal.

However, you have to cast or suffix the literal appropriately when assigning to anyhting other than a Double, because any literal with an e or E in it is recognized as a Double in Visual Studio. I cannot find where this behavior is specified.

float f1 = 7E1;     // Compile error. Needs F suffix (7E1F)
decimal d1 = 8E2;   // Compile error. Needs M suffix (8E2M)
double d2 = 9E3;    // Works.

int overninethousand = (int)9E3 + 1; // Works

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