1bits_to_bits 7-bit = 6-bit + 6-bit
2lost_carry 6-bit = 6-bit + 6-bit
3extension 9-bit = 6-bit + 6-bit
4truncation 4-bit = 6-bit + 6-bit
5
6promote 7-bit = 4-bit + 6-bit
7promote_lost_carry 6-bit = 4-bit + 6-bit
8promote_extension 9-bit = 4-bit + 6-bit
9promote_truncation 4-bit = 4-bit + 6-bit
10