Instruction Set Limitions

8 Instructions, how hard can it be to program:

• Missing many instructions you would expect from later processor.
• Need to go back to basic math and Boolean logic.
• No subtract – Need to negate and add. Negate is complement and add 1.
• Operate instructions CMA IAC. Can be abbreviated CIA.
• No OR – If know bits not set can use TAD otherwise A OR B is NOT (NOT A AND NOT B).
• No stack, return address written to first location of subroutine
• No conditional jumps, only conditional skip next instruction.
• Data field to switch to in CDF is part of instruction, frequently changed with self modifying code.
• Original code has lots of tricks to save memory such as using instructions as data.