Properties of an Ideal ISA (Instruction Set Architecture):

1. Completeness – All essential operations (data transfer, arithmetic/logic, control, I/O) are provided so any computable function can be implemented.

2. Orthogonality – No special cases; any addressing mode can be used with any operation and any register. Instructions are independent and uniformly available.

3. Regularity / Symmetry – Uniform instruction format, consistent opcode field, operand interpretation. Simplifies decoding.

4. Efficiency – High code density, good performance, optimal use of registers/memory and support for high-level language constructs.

5. Expandability / Extensibility – Opcode space reserved for future instructions/extensions without redesign.

6. Compatibility & General Purpose – Balanced between hardware simplicity and software convenience; often includes support for interrupts, virtual memory and protection.

An ideal ISA thus simplifies compiler design, hardware decoding and pipelining while remaining complete and efficient.