Looking at types of Elixir byte data

elixir_data_bytes.exs

is_binary <<255::size(8)>> # => true
is_bitstring <<255::size(8)>> # => true
is_binary <<255::size(4)>> # => false
is_bitstring <<255::size(4)>> # => true

# So a binary is a bitstring but a bitstring isn't necessarily a binary.
# We can see that effect in pattern matching as well:

<<255::size(4)>> # => <<15::size(4)>>
<<x>> = <<255::size(4)>> # => MatchError!

# And we can pull apart a larger byte into bits.

<<x::size(2), y::size(2)>> = <<255::size(4)>> # => <<15::size(4)>>

# This also works for utf8 bytes

<<?j>> # => "j"
<<x::size(4), y::size(4)>> = <<?j>> # => "j"
<<x,y>> # => <<6,10>> (this isn't "j" because each variable is being treated as a full byte)
<<x::size(4), y::size(4)>> # => "j" (now the bits are concatenated together into a single byte)