What is the basic principle of the stop-and-copy garbage collection algorithm described in the chapter?

Correct answer: It divides memory into 'working memory' and 'free memory', copies only the accessible 'useful' pairs to the free memory when the working memory is full, and then swaps the roles of the two memory halves.

Explanation

The stop-and-copy garbage collection method maintains the illusion of infinite memory by recycling space. It works by having two memory spaces and, when one fills up, copying only the live data to the other space. This not only reclaims garbage but also compacts the live data, after which the roles of the two spaces are flipped.

Other questions

Question 1

According to the principles of designing a register machine, what are the two fundamental components that must be designed?

Question 2

In the register machine designed to compute the greatest common divisor (GCD) using Euclid's Algorithm, what is the specific purpose of the register named 't'?

Question 3

What data structure is identified as a crucial mechanism for implementing recursive processes, like the factorial function, on a register machine with a fixed number of components?

Question 4

In the register machine for the recursive factorial function, which registers are explicitly saved on the stack before a recursive call is made?

Question 5

The `make_new_machine` function constructs a basic machine model. According to Section 5.2.1, what two registers are initially included in this model's register table?

Question 6

In the implementation of list-structured memory using vectors, how is a pointer to a pair represented?

Question 8

In the explicit-control evaluator, which register is used to hold the environment in which an evaluation is to be performed?

Question 9

What feature of the explicit-control evaluator's design allows it to be tail-recursive?

Question 10

What is the primary distinction between the execution strategies of interpretation and compilation as presented in the chapter?

Question 11

Within the compiler's design, what does a linkage descriptor of 'return' signify for the generated code?

Question 12

To support a more powerful subroutine mechanism, the register-machine language is extended. How is the `go_to` instruction modified to support this?

Question 13

In the context of the stop-and-copy garbage collector, what is a 'broken heart'?

Question 14

When the explicit-control evaluator is processing a conditional expression, why must the 'env' register be saved before evaluating the predicate?

Question 15

In the compiled code for the recursive factorial function shown in Figure 5.17, what is the first instruction executed at the function's entry point, labeled 'entry1'?

Question 16

How does the 'pair' operation get implemented in the register machine model that uses a vector-based memory with a 'free' register?

Question 17

In the explicit-control evaluator, what is the purpose of the 'unev' register?

Question 18

What is the primary efficiency advantage of compilation over interpretation as discussed in the text?

Question 19

In the compiler's `preserving` function, when are `save` and `restore` instructions actually generated for a register?

Question 20

What is the role of the `flag` register in the simulated register machine?

Question 21

How is a `save(reg)` instruction implemented in the model where the stack is represented as a list pointed to by the `the_stack` register?

Question 22

What is the role of the 'root' register in the stop-and-copy garbage collector?

Question 23

In the controller for the recursive Fibonacci machine (Figure 5.12), why is the `val` register saved before the second recursive call (`go_to(label("fib_loop"))`) but not before the first?

Question 24

How does the assembler, described in Section 5.2.2, resolve references to labels in the controller code?

Question 25

In the compiler implementation, what three pieces of information are contained within an instruction sequence data structure?

Question 26

How does the explicit-control evaluator handle the evaluation of a sequence of statements?

Question 27

What is the key difference in how the compiler and the interpreter handle the function expression part of an application like `f(96, 22)` where `f` is a name?

Question 28

In the stop-and-copy garbage collection algorithm, what is the purpose of the 'scan' pointer?

Question 29

How does the explicit-control evaluator apply a compound (non-primitive) function?

Question 30

According to footnote 37 in Section 5.5, why can the machine that runs compiled code be simpler than the interpreter machine?

Question 31

What is the function of the `continue` register in the register machines described for implementing subroutines and recursion?

Question 32

In the stop-and-copy garbage collector's main loop, what condition signals that the collection process is complete?

Question 33

Why does the `compile_lambda_expression` function in the compiler generate code for the function body immediately after the code for constructing the function object?

Question 34

What is the primary purpose of lexical addressing as a compiler optimization?

Question 35

In the explicit-control evaluator, how is a primitive function application handled at the `primitive_apply` label?

Question 36

The assembler uses the function `extract_labels` to process the controller list. What two values does this function effectively return to its continuation (`receive`)?

Question 37

According to the instruction summary in Section 5.1.5, which instruction is used to pop a value from the stack and place it into a register?

Question 38

In the vector-based memory representation, what is used to distinguish a pointer to a pair from a pointer to a number or other data type?

Question 39

When compiling a conditional expression, why does the `preserving` function save the `env` and `continue` registers around the code for the predicate?

Question 40

What is the key functional difference between the register machine instructions `branch` and `go_to`?

Question 41

In the explicit-control evaluator, how does the machine handle a return from a function if the function body terminates without executing a `return` statement?

Question 42

How many registers are specified for the explicit-control evaluator machine described in Section 5.4?

Question 43

What is the purpose of the `revert_stack_to_marker` instruction used in the explicit-control evaluator and compiler?

Question 44

In the GCD machine with a user interface (Figure 5.4), what kind of instruction is used to handle printing the result?

Question 45

When compiling the expression `f(g("x"), y)`, which registers must the compiler's `preserving` mechanism save around the code for the `g("x")` sub-expression?

Question 46

In the design of the explicit-control evaluator, which two registers are used to hold the result of `scan_out_declarations` and the corresponding list of `*unassigned*` values during the evaluation of a block?

Question 47

How many times will `vector_set` be called to implement the instruction `assign(reg1, list(op("pair"), reg(reg2), reg(reg3)))` in the vector-based memory model?

Question 48

What is the key problem with implementing a recursive function like `factorial` by simply decrementing the `n` register and re-running the machine from the beginning?

Question 49

In the context of interfacing compiled code with the evaluator, how is the evaluator modified to handle calls to compiled functions?

Question 50

According to the analysis in Section 5.5.7, how did the number of stack pushes for computing factorial(5) compare between the interpreted and compiled versions?