TAOCP 1.3.1 Exercise 5

Let (6) be a MIX word written in its physical layout as (6):\quad \pm \; \text{AA} \; \text{I} \; \text{F} \; \text{C}, where AA is the address field, I the index field, F the field specification, and...

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Section 1.3.1: Description of MIX

Exercise 5. [10] What symbolic notation, analogous to (4), corresponds to (6) if (6) is regarded as a MIX instruction?

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Let (6) be a MIX word written in its physical layout as

$$ (6):\quad \pm ; \text{AA} ; \text{I} ; \text{F} ; \text{C}, $$

where AA is the address field, I the index field, F the field specification, and C the operation code.

In symbolic MIX notation (as in (4)), the instruction is written using the mnemonic corresponding to the operation code, followed by the address, index, and field specification:

$$ \text{OP } \text{ADDRESS}, I(F). $$

To convert (6) into this form, we apply the field correspondences explicitly:

  • the operation code field $C$ is replaced by its mnemonic $\text{OP}$,
  • the address field $\text{AA}$ becomes the symbolic address,
  • the index field $\text{I}$ remains the index specifier,
  • the field specification $\text{F}$ becomes $(F)$,
  • the sign is ignored in the symbolic instruction form, since it is not part of instruction syntax.

Thus (6) corresponds to the symbolic instruction

$$ \boxed{\text{OP } \text{AA}, I(F)}. $$

Here OP is the mnemonic determined by the operation code $C$, i.e., $\text{OP} = \text{mnemonic}(C)$.