MariaDB CONNECT engine BIN table - file record layout, storage of a date data type, padding
1   0   0   0  -- 1; note "little-endian"
49  50  51  52  53  54  55  56  57  48  -- ascii/utf8 for "1234567890"
32  32  32  32  32  32  32  32  32  32
32  32  32  32  32  32  32  32  32  32 -- lots of spaces for padding
48  93  116 73   -- must be the date?
97  98  99  100 101   -- ascii/utf8 for 'abcde'
32  32  32  32  32
32  32  32  32  32   -- lots of spaces for padding
184 30  133 235 1   106 248 64  -- 100000.12 --&gt; hex: 40 f8 6a 01 eb 85 1e b8
210 4   0   0  -- 1234 = 210 + 4*2^8 + 0 * 2^16 + 0 * 2*24


On INT(4), the (4) has no meaning (unless you also use ZEROFILL).  INT is always 4 byte, but not because of (4).

DOUBLE is always 8 bytes; (m,n) should not be used.

The spaces are padding CHAR(n) CHARACTER SET utf8 out to 3 bytes per character.  This is an argument for almost always using VARCHAR, not CHAR.

With utf8mb4 there would be even more spacing.