The document states: >"In order to reduce the complexity a bit, all the decoding of the operand fields is done first and then the instruction is executed by on

The document states: >"In order to reduce the complexity a bit, all the decoding of the operand fields is done first and then the instruction is executed by one of many hundred small methods that don't have to care(much) about their operands." I'm confused by this, the operands are decoded first and then the op code is decoded? Or am I reading this incorrectly?