BCR is a family of radix-to-numeral encodings (such as BTTs) for positional numeral systems. The most well-known members being BCD and BCT.
These encodings allow efficient operations on radix N raw data and numeric values, while trading-off “minimal” memory (especially the “packed” variants).
Binary-coded-octal is just binary segmented in non-overlapping fixed-size triplets of bits, for the same reason ternary-coded-nonary is just ternary in pairs of trits: It’s all about powers.
This implies modern computers use binary-coded-base0x100, because the smallest addressable unit is an octet of bits