TAOCP 1.3.1 Exercise 3
The instruction format of a MIX word places the sign in position $0$, the address in bytes $1$–$2$, the index specification in byte $3$, the field specification in byte $4$, and the operation code in...
Section 1.3.1: Description of MIX
Exercise 3. [02] Give the partial field specifications, (L:R), for the (a) address field, (b) index field, (c) field field, and (d) operation code field of a MIX instruction.
Verified: yes
Solve time: 44s
The instruction format of a MIX word places the sign in position $0$, the address in bytes $1$–$2$, the index specification in byte $3$, the field specification in byte $4$, and the operation code in byte $5$.
The address field occupies the sign together with bytes $1$ and $2$, hence it is $(0:2)$. The index field is byte $3$, hence $(3:3)$. The field specification is byte $4$, hence $(4:4)$. The operation code is byte $5$, hence $(5:5)$. This completes the specification of all fields. ∎