Flag Manipulation and a Processor Control Instructions These instructions control the functioning of the available hardware inside the processor chip. These instructions are categorized into two types: Flag Manipulation instructions. Machine Control instructions. 1. Flag Manipulation instructions The Flag manipulation instructions directly modify the carry flag. These are STC - Set the carry Flag CMC - Complement the carry Flag 2. Machine Control instructions The Machine control instructions control the bus usage and execution HLT – Halt the process. NOP – No operation. DI     -  Disable Interrupt EI     - Enable Interrupt