2.2.2.3 Bit patterns of characters

The representation in machine words uses the least significant byte as tag:

00000000 00000000 00000000 00001010 value=#\nul C_make_character('\0')
00000000 00000000 01000001 00001010 value=#\A   C_make_character('A')

Characters do not make full use of the available bits, because the lower byte’s high nibble is always 0000. This means that only 24 bits are available for representing the character on 32-bit platforms; luckily, this is enough for representing the full Unicode range. If Unicode ever starts using up a bigger code space, we can always sneak in 4 more bits.

The preprocessor macro C_make_character() is defined in the header file chicken.h.