Confused with variable types

[TpOreilly]

Ive come across a variable named float which has a range of 3.4E to 38.

I understand that its for floating point devision numbers.

But i dont understand the range numbers, what does the letter "E" mean or represent after the 3.4 number?

Im new to programming btw

Thanks :)

[Disch]

that's scientific notation and isn't really specific to programming. It's more of a mathematical thing.

3.4e38 is 3.4 * 10^38 or 340000000000 ... (37 zeros)

[TpOreilly]

ermm ok....

can you tell me in words whats going on there?

[Galik]

Its a way to separate the digits of a number from their magnitude in 'powers of ten'. Instead of writing down bunches of zeros all the time mathematicians came up with a short hand notation where they just write the number of zeros down rather than the zeros themselves.

So instead of writing 100000000 I can just say 1x10⁸

That works because 10⁸ = 10x10x10x10x10x10x10x10 = 100000000

[TpOreilly]

ok thanks, i kinda get that, but im just wondering, what actual word the "e" short for, is it short for a word, or is "e" just "e" on its own :)

[Duthomhas]

It is short for 'exponent'.

1.2e4 is the same as 1.2x10⁴ is the same as 12000.

Hope this helps.

[TpOreilly]

thanks for all the replies, its coming clearer :)

its confusing me because in my book ive got it says:

type: float values: 3.4e +/- 38 (seven significant digits)

[Disch]

that's saying the largest number is 3.4e38 and the smallest (nonzero) number is 3.4e-38

negative exponents are the same thing. 1.2e-4 is the same as 1.2x10^-4 is the same as 0.00012

[TpOreilly]

Thanks alot

[TpOreilly]

oh, one last thing, what does the"(seven significant digits)" mean

[Disch]

It means that while numbers can be very large or very small, they can only have 7 (nonzero) digits.

For example the number 76543210000000 probably could be represented, but the number 11111111111111 probably couldn't be.

Even though 111... is smaller than 765.... it has more significant digits.

[TpOreilly]

ok, so because the value of float is 3.4e +/- 38, does this mean this is correct:

the largest number is:

340000000000000000000000000000000000000 (37 zeros)

and the smallest number is:

00000000000000000000000000000000000000.34 (37 zeros)

are floating point numbers just numbers with decimal places, which are used for precise variables?

[lilactiger89]

Almost! Watch where you put your points :-)

0.000000000000000000000000000000000000034 (37 zeros)
not
00000000000000000000000000000000000000.34 (37 zeros)

floats will probably do you for most purposes. If you really need something more precise then use a double (which has a greater range)
http://www.cplusplus.com/doc/tutorial/variables/

[TpOreilly]

oh yh lol

Thanks