What is this encoding? 0x21

Question

I am reading about ASCII and the book said that ! was represented as 0x21.

Now I know that ! is the binary 00100001 in the ASCII table, which is also 33 in decimal, which converted to hex is 21. But what is this 0x part of the encoding 0x21?

Solution

0x is the prefix used for hexadecimal numbers in almost every C-like programming language, so it has become the de-facto standard when writing hex numbers.

Sometimes you may also find hexadecimal numbers denoted by the h suffix (many assembly dialects follow this convention), or (in BASIC dialects) by the &H prefix.

Comments

[richard]

Why are they encoded into Hex? What would it be used for? Why not just use their binary or decimal values?

[Matteo Italia]

@Richard: hex is often used for values that have some particular significance in binary because hex is compact b the conversion from/to hex is straightforward. Also, groups of bits multiple of 4 stay in fixed length hex numbers (one "normal" byte is always two hex digits).

[fyr]

@Richard thats pretty easy developers are lazy. And numbers to the base of 16 are shorter than numbers to the base of 10 or 8 or 2 ... :) and they also can be easily translated to a binary string. Because every hex character can be translated to a 4 character binary respresentation.

[Matteo Italia]

Other than these motivations, in reality often hex is used for constants for no other reason than being "cool" and 1337 :)