Instruction Summary

A controller instruction in our register-machine language has one of the following forms, where each <input_i> is either (reg <register-name>) or (const <constant-value>).

These instructions were introduced in section 5.1.1:

(assign <register-name> (reg <register-name>))

(assign <register-name> (const <constant-value>))

(assign <register-name> (op <operation-name>) <input₁> ... <input_n>)

(perform (op <operation-name>) <input₁> ... <input_n>)

(test (op <operation-name>) <input₁> ... <input_n>)

(branch (label <label-name>))

(goto (label <label-name>))

The use of registers to hold labels was introduced in section 5.1.3:

(assign <register-name> (label <label-name>))

(goto (reg <register-name>))

Instructions to use the stack were introduced in section 5.1.4:

(save <register-name>)

(restore <register-name>)

The only kind of <constant-value> we have seen so far is a number, but later we will use strings, symbols, and lists. For example, (const "abc") is the string "abc", (const abc) is the symbol abc, (const (a b c)) is the list (a b c), and (const ()) is the empty list.

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Structure and Interpretation of Computer Programs by Harold Abelson and Gerald Jay Sussman with Julie Sussman is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License by the MIT Press. Modifications to the material were made by syntaxhelper.com.