What is 0x10 in decimal?

I have the following code:

SN.get_Chars(5)

SN is a string so this should give the 5th Char. Ok!

Now I have another code but: SN.get_Chars(0x10)

I wonder what 0x10 is? Is it a number? If it's so, then what is it in decimal notation?

0x means the number is hexadecimal, or base 16.

0x10 is 16.

paxdiablo

0xNNNN (not necessarily four digits) represents, in C at least, a hexadecimal (base-16 because 'hex' is 6 and 'dec' is 10 in Latin-derived languages) number, where N is one of the digits 0 through 9 or A through F (or their lower case equivalents, either representing 10 through 15), and there may be 1 or more of those digits in the number. The other way of representing it is NNNN₁₆.

It's very useful in the computer world as a single hex digit represents four bits (binary digits). That's because four bits, each with two possible values, gives you a total of 2 x 2 x 2 x 2 or 16 (2⁴) values. In other words:

  _____________________________________bits____________________________________
 /                                                                             \
+----+----+----+----+----+----+----+----+----+----+----+----+----+----+----+----+
| bF | bE | bD | bC | bB | bA | b9 | b8 | b7 | b6 | b5 | b4 | b3 | b2 | b1 | b0 |
+----+----+----+----+----+----+----+----+----+----+----+----+----+----+----+----+
 \_________________/ \_________________/ \_________________/ \_________________/ 
      Hex digit           Hex digit           Hex digit           Hex digit

A base-X number is a number where each position represents a multiple of a power of X.

In base 10, which we humans are used to, the digits used are 0 through 9, and the number 7304₁₀ is:

(7 x 10³) = 7000₁₀ ; plus
(3 x 10²) = 300₁₀ ; plus
(0 x 10¹) = 0₁₀ ; plus
(4 x 10⁰) = 4₁₀ ; equals 7304.

In octal, where the digits are 0 through 7. the number 754₈ is:

(7 x 8²) = 448₁₀ ; plus
(5 x 8¹) = 40₁₀ ; plus
(4 x 8⁰) = 4₁₀ ; equals 492₁₀.

Octal numbers in C are preceded by the character 0 so 0123 is not 123 but is instead (1 * 64) + (2 * 8) + 3, or 83.

In binary, where the digits are 0 and 1. the number 1011₂ is:

(1 x 2³) = 8₁₀ ; plus
(0 x 2²) = 0₁₀ ; plus
(1 x 2¹) = 2₁₀ ; plus
(1 x 2⁰) = 1₁₀ ; equals 11₁₀.

In hexadecimal, where the digits are 0 through 9 and A through F (which represent the "digits" 10 through 15). the number 7F24₁₆ is:

(7 x 16³) = 28672₁₀ ; plus
(F x 16²) = 3840₁₀ ; plus
(2 x 16¹) = 32₁₀ ; plus
(4 x 16⁰) = 4₁₀ ; equals 32548₁₀.

Your relatively simple number 0x10, which is the way C represents 10₁₆, is simply:

(1 x 16¹) = 16₁₀ ; plus
(0 x 16⁰) = 0₁₀ ; equals 16₁₀.

As an aside, the different bases of numbers are used for many things.

base 10 is used, as previously mentioned, by we humans with 10 digits on our hands.
base 2 is used by computers due to the relative ease of representing the two binary states with electrical circuits.
base 8 is used almost exclusively in UNIX file permissions so that each octal digit represents a 3-tuple of binary permissions (read/write/execute). It's also used in C-based languages and UNIX utilities to inject binary characters into an otherwise printable-character-only data stream.
base 16 is a convenient way to represent four bits to a digit, especially as most architectures nowadays have a word size which is a multiple of four bits.
base 64 is used in encoding mail so that binary files may be sent using only printable characters. Each digit represents six binary digits so you can pack three eight-bit characters into four six-bit digits (25% increased file size but guaranteed to get through the mail gateways untouched).
as a semi-useful snippet, base 60 comes from some very old civilisation (Babylon, Sumeria, Mesopotamia or something like that) and is the source of 60 seconds/minutes in the minute/hour, 360 degrees in a circle, 60 minutes (of arc) in a degree and so on [not really related to the computer industry, but interesting nonetheless].
as an even less-useful snippet, the ultimate question and answer in The Hitchhikers Guide To The Galaxy was "What do you get when you multiply 6 by 9?" and "42". Whilst same say this is because the Earth computer was faulty, others see it as proof that the creator has 13 fingers :-)

It's a hex number and is 16 decimal.

Notice that '10' is the representation of the base in that base:

10 is 2(decimal) in base-2

10 is 3(decimal) in base-3

...

10 is 10(decimal) in base-10

...

10 is 16(decimal) in base-16 (hexadecimal)

...

10 is 1024(decimal) in base-1024

...and so on

The simple version is 0x is a prefix denoting a hexadecimal number, source.

So the value you're computing is after the prefix, in this case 10.

But that is not the number 10. The most significant bit 1 denotes the hex value while 0 denotes the units.

So the simple math you would do is

0x10

1 * 16 + 0 = 16

Note - you use 16 because hex is base 16.

Another example:

0xF7

15 * 16 + 7 = 247

You can get a list of values by searching for a hex table. For instance in this chart notice F corresponds with 15.

来源：https://stackoverflow.com/questions/692286/what-is-0x10-in-decimal

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