# What is \`Char\`?

**URL:** <https://discourse.julialang.org/t/what-is-char/8480>\
**Category:** General Usage\
**Created:** [January 19, 2018, 4:48pm UTC](https://discourse.julialang.org/t/what-is-char/8480 "2018-01-19T16:48:14Z")\
**Posts on this page:** 7\
**Page:** 1

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**Author:** ![ExpandingMan](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/expandingman/32/866_2.png) [@ExpandingMan](https://discourse.julialang.org/u/ExpandingMan)\
**Post date:** [January 19, 2018, 4:48pm UTC](https://discourse.julialang.org/t/what-is-char/8480/1 "2018-01-19T16:48:14Z")

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Here’s something that came as a surprise

```julia
A = UInt8['a', 'b', 'c']

ptr = convert(Ptr{Char}, pointer(A))

a = unsafe_load(ptr, 1) # this is not 'a'; it is '\U636261'

```

so Julia for some reason decided to load a 24-bit `Char` (correction: no, it’s actually 32 bit, see below). I’m guessing that people are going to tell me that the right way to go about doing this is simply to load a `UInt8` and convert to `Char` (not ideal as it requires special handling in code which is designed to load generic stuff). I don’t even know why it stopped at 24 bits and not 16 or 32. Is there a way of loading directly to an 8-bit `Char`? I’m now pretty confused about what a `Char` even is.

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**Author:** ![sdanisch](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/sdanisch/32/1406_2.png) [@sdanisch](https://discourse.julialang.org/u/sdanisch)\
**Post date:** [January 19, 2018, 5:08pm UTC](https://discourse.julialang.org/t/what-is-char/8480/2 "2018-01-19T17:08:14Z")

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Char represents a 32 bit Unicode code point ( I think :D) so the translation from `x[idx]::UInt8` is not straight forward and you might need multiple (up to 4) UInt8 elements to construct a valid char from an uint8 utf8 string array.  
On 0.6 & 0.7 I get a 32 bit char out of this, which is what you expect.  
What you do should be an out of bounds error, wouldn’t it be for the `unsafe`, since your array only has 24 bit 😉

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**Author:** ![ExpandingMan](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/expandingman/32/866_2.png) [@ExpandingMan](https://discourse.julialang.org/u/ExpandingMan)\
**Post date:** [January 19, 2018, 5:24pm UTC](https://discourse.julialang.org/t/what-is-char/8480/3 "2018-01-19T17:24:45Z")

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Sorry, correction to the above: when I do `sizeof(a)` I do indeed get `4`. I was confused because `\U636261` _looks_ 24-bit. Evidently you are right @sdanisch, they are always 32-bit.

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**Author:** ![ScottPJones](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/scottpjones/32/146_2.png) [@ScottPJones](https://discourse.julialang.org/u/ScottPJones)\
**Post date:** [January 19, 2018, 9:09pm UTC](https://discourse.julialang.org/t/what-is-char/8480/4 "2018-01-19T21:09:05Z")

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You are casting a pointer to `UInt8` into `Char`, which is a 32-bit quantity.  
That’s why you are seeing the 3 characters packed into that one 32-bit word (along with a trailing \0).

In master, `Char` is not even simply a Unicode code point (i.e. `0-0xd7ff`, `0xe000-0x10ffff`) anymore,  
it is a rather complex method of packing a 1 to 4 byte UTF-8 encoding of a Unicode code point into a 32-bit value, and also allowing storing invalid UTF-8 1 to 4 byte sequences.

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**Author:** ![StefanKarpinski](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/stefankarpinski/32/24_2.png) [@StefanKarpinski](https://discourse.julialang.org/u/StefanKarpinski)\
**Post date:** [January 19, 2018, 10:30pm UTC](https://discourse.julialang.org/t/what-is-char/8480/5 "2018-01-19T22:30:21Z")

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> [@ScottPJones](#):
>
> In master, `Char` is not even simply a Unicode code point (i.e. `0-0xd7ff`, `0xe000-0x10ffff`) anymore, it is a rather complex method of packing a 1 to 4 byte UTF-8 encoding of a Unicode code point into a 32-bit value, and also allowing storing invalid UTF-8 1 to 4 byte sequences.

It’s not really complicated at all. `Char` values are now just UTF-8 bytes padded with trailing zeros:

```julia
julia> reinterpret(UInt32, '∀')
0xe2888000

julia> codeunits("∀")
3-element Base.CodeUnits{UInt8,String}:
 0xe2
 0x88
 0x80

```

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<div class="post-metadata">

**Author:** ![ScottPJones](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/scottpjones/32/146_2.png) [@ScottPJones](https://discourse.julialang.org/u/ScottPJones)\
**Post date:** [January 20, 2018, 1:30pm UTC](https://discourse.julialang.org/t/what-is-char/8480/6 "2018-01-20T13:30:41Z")

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> [@StefanKarpinski](#):
>
> Char values are now just UTF-8 bytes padded with trailing zeros:

And that is very complex, compared to simply having the code point stored as its numerical value.  
As I showed elsewhere, the difference in code generated to pack and unpack that UTF-8 based format is very large (it’s a noop in v0.6 and earlier versions of Julia to go between `Char` and `UInt32`)  
It also means that you can’t share a `Vector{Char}` any more with a C/C++ array of `wchar_t` (when it is 32-bit) or `char32_t`.

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**Author:** ![nalimilan](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/nalimilan/32/147_2.png) [@nalimilan](https://discourse.julialang.org/u/nalimilan)\
**Post date:** [January 20, 2018, 2:47pm UTC](https://discourse.julialang.org/t/what-is-char/8480/7 "2018-01-20T14:47:46Z")

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Can we avoid having this discussion again please?