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32 Part 1 ½ Fundamentals Section 1 ½ Abstraction and Notation


The foregoing examples should allow the reader to understand all the IS PS descriptions in the book. All the descriptions follow a standard format:

Memory declarations




MP state

PC state

External state

Implementation declarations

Formats and operations

Instruction format

Address calculation

Service facilities


Instruction interpretation

Instruction set


The implementation declarations are required for temporary storage in complex expression evaluations. These variables probably have similar, if not identical, counterparts in the actual machine implementation. However, these variables are invisible to the programmer and hence are not mentioned in the programmer's manual.

The following conventions for capitalization have been adopted. Architectural features, instruction mnemonics, and other names that are capitalized in the manufacturer's literature are in uppercase in the JSPS descriptions to aid recognizability. To aid readability, all ISPS operators that affect control flow are in uppercase. These include: DECODE, IF, RESTART, LEAVE, REPEAT, RESUME, STOP, and WAIT. Everything else is lowercase, including operators (e.g., eql, eqv, leq, lss, mod, neq, no.op, not, or, sl0, sl1, sld, slr, sr0, sr1, srd, srr, tst, and xor), ISPS implementation variable, and the remaining ISPS reserve words (e.g., begin, end, next).

All the ISPS descriptions that appear in this book have been compiled and simulated. The descriptions are complete, except for the instruction-set portion in large machines. In order to keep the size of the descriptions in bounds, we have deleted all but a representative instruction of each op code decoding group for these large machines. Nevertheless, these partial ISPS descriptions have been compiled and simulated.

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