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 :

(assign register-name (reg register-name))


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


(assign register-name (op operation-name) input1 ... inputn)


(perform (op operation-name) input1 ... inputn)


(test (op operation-name) input1 ... inputn)


(branch (label label-name))


(goto (label label-name))

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

(assign register-name (label label-name))


(goto (reg register-name))

Instructions to use the stack were introduced in section :

(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.